Abstracts are listed alphabetically by presenting author in two lists: Oral Presentations and Poster Presentations.
Nondiffusive Electron Acceleration From Resonant VLF Waves
Jay Albert (Boston College and Air Force Research Laboratory; firstname.lastname@example.org)
Storm-time acceleration of outer zone electrons is an outstanding unsolved problem. Several theories invoke VLF waves, either for direct acceleration or in cooperation with ULF waves. Recent work has analyzed the gyroresonant interaction of a particle with VLF waves using a Hamiltonian approach that accounts for the passage through resonance in the spatially varying geomagnetic field. Under certain conditions, phase trapping can cause pitch angle and energy to change deterministically rather than diffusively, so that the cumulative effect of many interactions is much greater than usually supposed. Here, these results are applied to outer zone electrons, to see if storm-time acceleration is a plausible outcome of this mechanism.
The Climatology of the Earth's High-Energy Electron Environment
D. N. Baker (email@example.com), S. G. Kanekal, and X. Li (all at Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA)
Long-term observations of relativistic magnetospheric electrons (E > 0.5 MeV) have in the past been made principally at geostationary Earth orbit (GEO). Some of these homogeneous data sets extend back to the 1970s and such data reveal significant solar-cycle (~11-year) variations of electron flux. Establishing such long-term ``climatology'' for electron populations is very important for spacecraft design considerations, space operations, and other practical purposes. Newer data sets especially those from the SAMPEX and POLAR missions are now allowing us to describe the climatology of high-energy electrons at many other L-values besides at GEO (i.e., at L-values other than just L=6.6). We have assembled a year-by-year view of all relevant L-shells from SAMPEX sensors, for example, from 1992 to the present. We have made comparisons to concurrent solar wind measurements and to other putative geomagnetic ``drivers''. Our observations and analyses should be valuable to spacecraft designers, operators and to International Space Station planners.
Long term observations of radiation belt electrons by STRV
P. Bühler1 (firstname.lastname@example.org), L. Desorgher2, E. Daly3, A. Zehnder1. 1 Paul Scherrer Institute, Laboratory for Astrophysics, CH-5232 Villigen PSI; 2 University of Bern, Space Research & Planetary Sciences, CH-3012 Bern; 3 ESA/ESTEC, Space Environments and Effects Analysis Section, NL-2200 AG Noordwijk.
In June 1994 the UK satellites Strv-1b and 1c were launched into a nearly equatorial geostationary transfer orbit (GTO). As part of the scientific payload one satellite carried the particle detector REM which measured high energetic protons and relativistic (>1 MeV) electrons. In this paper we summarize the results on the outer radiation belt electrons, obtained with the data from REM during its four years of operation.
The high energy tail of the outer radiation belt is subject to strong variations with time-scales reaching from a fraction of a day to the period of the solar cycle, and which are strongly influenced by the solar wind and interplanetary magnetic field (IMF) conditions. Our analysis aimed at characterizing different types of variations and at defining the underlying physical processes. This was striven for by detailed analysis of specific time periods but also long term correlation studies with solar wind, IMF, and geomagnetic activity parameters.
Radiation Belt Transport Theory Using Phase-Space Lagrangian Methods
Anthony A. Chan (Department of Physics and Astronomy, Rice University, Houston, Texas, USA; email@example.com) and Alain J. Brizard (Department of Physics, Saint Michael's College, Colchester, Vermont, USA)
Radiation belt transport theory is based on the theory of adiabatic invariants and has been developed in the classic work of Alfvén , Northrop and Teller , Kruskal , Roederer , and Schulz and Lanzerotti , among others. More recently, a powerful and general formulation of adiabatic invariant theory and plasma transport has been developed using phase-space Lagrangian (PSL) methods [Littlejohn, 1983; Brizard, 1989; Chan et al, 1989]. These methods provide an elegant mathematical formulation of guiding center theory, adiabatic invariants, and plasma transport theory using noncanonical Hamiltonian mechanics and they have several advantages over earlier formulations. We have applied the PSL methods to derive equations of motion and kinetic equations for relativistic particles (electrons) in magnetospheric field configurations. The resulting guiding center equations of motion conserve energy in static magnetic fields (whereas the guiding center equations of Northrop  and Roederer  do not), and the PSL methods allow a rigorous explicit derivation, for the first time, of the well-known (Fokker-Planck) radiation belt transport equation. The PSL methods will be outlined, the advantages and disadvantages of the methods will be discussed, and new expressions for relativistic electron diffusion coefficients due to ULF wave-particle interactions will be presented.
Mapping the Radiation Belts: Frequency Distribution Functions
Norma B. Crosby (University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK; email: firstname.lastname@example.org).
The radiation belts have been found to be dynamical on all spatial and time scales. As many spacecraft cross through this region of geo-space it is crucial to map them as precisely as possible, indicating where the probability of exceeding a given measured threshold value is highest. Frequency distribution functions of measured radiation belt parameters are shown to be well-represented by power-laws over a couple of decades. Using measurements from various spacecraft, the probability of having a flux value over a given value is investigated as a function of L-shell and local magnetic time. The results offer new information in the mapping of this not well-measured region of geo-space. Furthermore applying the concept of self-organised criticality to interpret the shape of the distribution functions suggests another approach in the understanding of this complicated environment.
In-flight discriminating Energetic Particle Telescope (EPT): Design Methodology
M. Cyamukungu (UCL/FYNU/CSR, Belgium; email: email@example.com), Gh. Gregoire (UCL/FYNU/CSR, Belgium) and J. Lemaire (UCL/ASTR and BISA, Belgium)
The raw data acquired by detectors of various charged particle species (electrons, protons and heavy ions) on board satellites usually need to be re-processed to extract particle fluxes, fluences, doses,...
The most time consuming task of the post-processing phase is the conversion of the instrument outputs (counting rates, current, voltage,...) into physically meaningful angle and energy-dependent fluxes. In particular, the so-called ``corrected geometrical factors'' are used for counting rate conversion into fluxes. The deconvolution of particle spectra and angular distribution, taking into account the angle and energy-dependent intrinsic detection efficiencies of each channel and particle type, is the most accurate method to obtain directional particle fluxes. Of course, the amount of computational resources needed to apply this more general method increases dramatically with the number of particle species to discriminate, especially when several particle species are detected by the same channel.
The Energetic Particle Telescope (EPT) is a 30 deg. field-of-view detector equipped with 96 energy channels (24 channels for each particle). It has been designed to provide users with an instrument that directly outputs spectra of electrons (0.1 - 10 MeV), protons (1 - 300 MeV), Helium ions (4 - 500 MeV) and Lithium ions (10 - 500 MeV). This goal was reached by extensive use of the GEANT Monte-Carlo simulation code and in-beam tests at each phase of the design. The whole design methodology and the present status of the instrument development will be presented.
Radial diffusion in a non-axisymmetric magnetic field: towards a generalized theory of radial diffusion
S. R. Elkington (Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303; email: firstname.lastname@example.org), A. A. Chan (Department of Physics and Astronomy, Rice University, Houston, TX 77005), M. K. Hudson (Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755), I. R. Mann (Magnetospheric Physics Group, University of York, Heslington, York, YO10 5DD, UK)
Electric and magnetic field variations, occurring on time scales commensurate with the drift period of a trapped particle, can induce the particle into regions of higher or lower magnetic field strength through violation of the third adiabatic invariant. If the first adiabatic invariant is however conserved in this process, the particle will gain or lose energy in its radial drift across L shells. Stochastic electric field variations at ULF frequencies have long been recognized as an important process affecting the energetic particles comprising the outer radiation belts. In an axisymmetric magnetic field these variations result in a radial diffusion of the particles, with diffusion rates scaling directly with the power in the ULF spectrum and varying radially as L6.
In a non-axisymmetric magnetic geometry, such as in a geomagnetic dipole distorted by the solar wind, new drift-resonant interactions between the particles and ULF waves are possible, resulting in additional modes of radial diffusion. In this work we compare these asymmetric diffusion modes with the traditional L6 diffusion that results in a dipole field geometry. We examine the combined effects of the symmetric and asymmetric diffusion modes on radiation belt particles, and address the effects of realistic local time and radial variations in ULF wave profiles.
Pc5 Hydromagnetic Waves in the Middle Magnetosphere: Modulation of Pc1 Ion Cyclotron Waves and the Role of Medium Energy Ions
B. J. Fraser (CRC for Satellite Systems, Physics Department, University of Newcastle, NSW 2308, Australia; email@example.com), Y. D. Hu (Now at: Weapons Systems Division, DSTO, P. O. Box 1500, Salisbury, SA 5108, Australia), A. Korth (MPAe, Katlenburg-Lindau, D-37189, Germany), H. J Singer, (NOAA, R/E/SE Space Environment Centre, Boulder, CO 80303, USA), D. A. Hardy (AFRL, Hanscom AFB, MA 01731, USA) R.R. Anderson (Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242)
The influence of compressional Pc5 ULF waves on the Pc1-2 electromagnetic ion cyclotron wave generation process involving medium energy ions in the middle magnetosphere is studied using CRRES observations. The two types of waves are seen simultaneously in association with magnetic storms. In the waves studied here, EMIC waves have a short duration in comparison with the Pc5 wave cycle and appear to be modulated by the Pc5 waves. There is also a tendency for the EMIC waves to increase in amplitude during the decrease in Pc5 wave magnetic field, with maximum EMIC wave power shifting to lower frequencies. From consideration of instability theory it is shown that the modulation of the EMIC waves by the Pc5 waves may not be controlled only through the variation of energetic ion temperature anisotropy in an adiabatic process which shows in-phase modulation, but also through the variation in the magnetic field on the ion cyclotron instability, and the variation of the number and energy density of the energetic ions in a non-adiabatic interaction with the Pc5 waves. These latter modulations will be discussed with respect to the CRRES magnetic field, wave and particle data analysed.
Parameterization of relativistic electron losses using GPS and HEO measurements and application to the Salammbo radiation belt code
R. H. W. Friedel (Los Alamos National Laboratory, firstname.lastname@example.org), S. Bourdarie (ONERA-CERT/DESP), J. F. Fennell (The Aerospace Corporation), T. Cayton (Los Alamos National Laboratory)
The dynamics of relativistic electrons in the inner magnetosphere has been a topic of considerable attention in recent years. While the main focus of research in this area has been directed at the understanding of the storm-time enhancements of relativistic electrons, the loss processes associated with even moderate geomagnetic activity is as puzzling and not nearly as well studied.
The GPS constellation of energetic particle detectors covers the inner region from L=4 outward at sub-hour resolution. We routinely observe abrupt flux gradients, indicative of the satellite having left the relativistic electron trapping boundary. Observation of this boundary is only limited by instrument counting statistics; generally the boundary has to be below L=8 to be discernible above background levels.
We present here a statistical study of the relativistic electron trapping boundary as observed by the GPS constellation since 1997. We further intent to increase our relativistic electron trapping boundary detection time resolution by applying the same methods developed for GPS to HEO data.
The Salammbo radiation belt code has been fairly successful at modeling the dynamics of relativistic electrons during disturbed times. To date this code has not included the catastrophic losses (dropouts) associated with relativistic electron dynamics. We intend to present the first model runs incorporating the the relativistic electron trapping boundary as established by GPS and HEO.
Radiation Belt Science Objectives for Living with a Star
B. L. Giles, R. A. Hoffman and J. L. Barth (NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States; email: email@example.com), B. H. Mauk and L. J. Zanetti (Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099 United States), G. D. Reeves (Los Alamos National Laboratory, Los Alamos, NM 87545 United States)
The radiation belt science initiative of NASA's Living with a Star (LWS) program will enable understandings of the sources, transport and losses of radiation belt particles. Special emphasis will be directed toward penetrating radiation associated with geomagnetic storms. To gain these understandings, plasma measurement requirements have to include coverage of phase space distributions over local time and altitude of the most important radiation belt particles and electric and magnetic fields over the frequency domains of interest to the radiation belts. The data acquired and these understandings will lead to the development of empirical and three dimensional dynamic science-driven radiation belt models with short scale (magnetic storm) to long scale (solar cycle) temporal characteristics.
A review of the pre-definition stage science objectives and mission constraints will be presented. Emphasis will be placed upon the measurement requirements and analysis methods necessary for the in-situ measurements to be transformed into reconstructions of a dynamic global picture. A broad exchange of ideas and concepts is advantageous in preparation for the formal science definition team process and the subsequent development of level 1 program plan requirements for the mission.
Simultaneous simulation of the Global (MHD) Magnetosphere and Radiation Belt (Kinetic) Energetic Ions and Electrons
C. Goodrich (University of Maryland, firstname.lastname@example.org), M. Hudson (Dartmouth College), J. G. Lyon (Dartmouth College), M. Wiltberger (Dartmouth College) and S. Elkington (University of Colorado).
We present the results of a project supported by NSF to compute simultaneously the global structure of the magnetosphere using the Lyon-Fedder-Mobarry MHD code and the kinetic particle codes developed at Dartmouth by Elkington and Hudson. We have used both codes to obtain excellent results for the radiation belt environment for several magnetic storms. However, the codes were used sequentially for these studies. We first stored the time series of MHD electric and magnetic fields on disk, then read the data, after several data conversions, into the kinetic code to drive the tracing of energetic ions and electrons. We now can run the codes together asynchronously, and pass the fields as they are produced in the MHD code to the kinetic code. At present the particle calculations follow the bounce averaged particle trajectories in two dimensions, and the appropriate two dimensional slice of MHD fields are passed. In the near future, we will move to three dimensional tracing of the particles requiring access to the full MHD field structure in the inner magnetosphere, and tighter coupling of the codes.
Relation Between Dst and Relativistic Electrons During Magnetic Storms
M. Grande (1,2)(M.Grande@rl.ac.uk), M. Carter (1), C. H. Perry (1), B. Blake (3), J. Fennell (3), R. Nakamura (4), G. Reeves (5). (1) Rutherford Appleton Lab, UK; (2) Warwick University, UK; (3) Aerospace Corp., California, USA; (4) MPI Garching, Germany; (5) LANL, USA
Conventionally Geomagnetic Storms are associated with increases in energetic electrons. We have used Polar and CRRES data to investigate the correlation between Dst and energetic electrons on a number of timescales. On a range of timescales, Dst excursions and the fluxes of energetic electrons actually seem to anticorrelate. Most obviously, the flux of relativistic electrons begins to increase at precisely the moment when Dst begins to recover.
This is not simply a question of adiabaticity. It appears that while the onset of a storm can indeed set up the conditions for an enhancement of the electrons, the immediate effect is actually to remove electrons from the system. It is also this effect which finally ends the lifetime of the new belt formed. We investigate the possible role of adiabaticity in reducing measured fluxes. Under this hypothesis, although relativistic electrons are seen immediately following Dst max excursion, the energisation process was going on before, but masked by adiabatic contraction of electron orbits due to the ring current. By comparing phase space density of electrons of fixed at different L values, we conclude that this explanation does not appear correct. Phase space density calculations are further employed to address the question of the source of stormtime energetic electrons. We find no evidence of an internal source.
Testing Relativistic Electron Acceleration Mechanisms
J. C. Green (email@example.com) and M. G. Kivelson (both at University of California, Los Angeles)
Observations of relativistic electrons show extreme temporal variations in flux that have been difficult to explain. Many theories have been proposed to account for the rapid changes in flux including the ``Dst effect'' [Dessler and Karplus, 1961; McIlwain, 1966; Rinaldi et al. 1994; Kim and Chan, 1997; Li et al., 1999; Selesnick et al. 2000], ULF wave resonance [Elkington et al. 1999; Hudson et al. , 1999], ULF compressional wave acceleration [Summers et al., 2000], VLF wave resonance [Summers, 1998; Horne and Thorne, 1998; Roth et al., 1999], simultaneous ULF and VLF wave interactions [Rostoker et al., 1998; Liu et al., 1999], and multi-mode diffusion [Beutier and Boscher, 1995; Bourdarie et al., 1996]. It is unclear which if any of these acceleration and loss mechanisms are relevant to the electron radiation belts.
The ``Dst effect'' states that relativistic electron fluxes observed at constant position and energy will mimic changes in the magnetic field as measured by Dst as the relativistic electrons move to conserve all three invariants. This effect can cause order of magnitude changes in flux that will obscure enhancements due to other acceleration processes. Using Polar HIST electron data we produce a dataset of phase space densities at constant invariants which are unaffected by slow changes in the magnetic field allowing us to identify enhancements due to other processes.
The ULF wave radial diffusion mechanism accelerates electrons by transporting them radially inward while conserving the first and second adiabatic invariant. The mechanism requires a source of electrons at large L and a phase density versus L profile with a positive slope. Other mechanisms accelerate electrons locally and will cause a local peak in phase space density. We test the ULF wave radial diffusion mechanism by analyzing phase space density versus L profiles for a series of relativistic electron phase space density enhancement events.
Electron Loss and Acceleration in the Outer Radiation Belt Associated with Whistler Mode Chorus and Enhanced Substorm Activity
Richard B. Horne (British Antarctic Survey, Cambridge, UK; firstname.lastname@example.org), Nigel P. Meredith and Roger H. A. Iles (Mullard Space Science Laboratory, UK), Richard M. Thorne (Department of Atmospheric Sciences, UCLA), Roger R. Anderson (Department of Physics and Astronomy, University of Iowa), and Daniel Heynderickx, (BIRA, Brussels, Belgium)
Recent work shows that 90% of magnetic storms are associated with electron acceleration to relativistic energies (MeV) in the outer radiation belt during the recovery phase. Here we analyse three case events using data from the CRRES satellite to provide information on the acceleration mechanism. In the first event, the electron flux in the outer radiation belt is enhanced by more than an order of magnitude over the pre-storm level during the recovery phase. The event is associated with strong substorm activity as measured by the AE index and enhanced whistler mode chorus. In the second event, there is no acceleration during the recovery phase of the storm. The event is characterised by a strong northward turning of the interplanetary magnetic field, little or no substorm activity in the recovery phase, and little or no enhancement in the whistler mode chorus. In the third event, we find evidence for electron acceleration during a period of prolonged substorm and whistler mode chorus activity in the absence of any moderate or stronger storm. Our analysis suggests that gradual electron acceleration in the radiation belts is associated with periods of prolonged substorm activity rather than magnetic storms, and that acceleration can occur in the absence of magnetic storms. Since substorm activity provides an enhanced seed population of electrons < 500 keV, and enhances whistler mode chorus, the data are consistent with electron acceleration by whistler mode waves.
Radiation Belt Particle Acceleration by ULF Wave Drift Resonance
M.K. Hudson (Mary.K.Hudson@dartmouth.edu), K.L. Perry and W.J. Wiltberger (all at Physics and Astronomy Dept., Dartmouth College Hanover NH 03755), S.R. Elkington (LASP, University of Colorado Boulder, CO 80303)
Coronal Mass Ejections (CMEs) and recurring high speed streams in the solar wind have been correlated with increased trapped MeV electron fluxes in the magnetosphere. Recent progress has been made in simulating the rise in trapped fluxes of MeV electrons, using a 3D global MHD simulation of solar wind interaction with the magnetosphere as a source of time-varying electric and magnetic field input to guiding center test particle simulations. Both rapid radial transport due to the induction electric field that results from a large amplitude compression of the magnetopause, e.g. the March 24, 1991 event, and more gradual boundary perturbations, such as that of January 10-11, 1997, and other recent ISTP events, have been simulated using this technique. A common feature is the excitation of ULF waves, eigenmodes of the magnetosphere which oscillate either in response to a rapid radial distortion of the boundary, or may be excited by shear flow (Kelvin-Helmholz instability) or directly transferred from solar wind fluctuations in the mHz frequency range. Substorms also produce power on the nightside in this frequency range. Whatever the origin of excitation, ULF waves have been seen in both groundbased and satellite measurements to be correlated with the rise in flux of relativistic electrons in the magnetosphere. The MHD simulations driven by measurements of solar wind parameters at or near the L1 point upstream from earth (historically at WIND and currently at ACE), exhibit electric and magnetic field oscillations at ULF wave frequencies. Such fluctuations give rise to enhanced radial diffusion. Inward diffusion leads to energization at a rate determined by first invariant conservation, hence L-3/2 for outer zone electrons, already relativistic above 0.5 MeV, and L-3 for protons. This transport produces enhancement of outer zone electron fluxes throughout the storm recovery phase period of enhanced ULF wave activity. The same mechanism can trap solar energetic protons and produce transient belts which last for days to weeks, depending on the level of subsequent geomagnetic activity.
Chorus emissions in the vicinity of the outer radiation belt correlated with magnetic storm
Yoshiya Kasahara (email@example.com), Hiroki Uchiyama, Yoshitaka Goto, Toru Sato (Dept. of Communications and Computer Eng., Kyoto Univ., Kyoto 606-8501, Japan Phone:+81-75-753-3365, Fax:+81-75-753-3342) Isamu Nagano (Dept. of Information and Systems Eng., Kanazawa Univ., Kanazawa 920-8667, Japan).
Akebono was launched in 1989 into a semi-polar orbit with an altitude range between 300km and 10,000km, and has been operated successfully for about 12 years. The VLF instruments onboard Akebono were designed to investigate VLF/ELF range plasma waves and to determine the wave normal direction of the waves. We investigate spatial and temporal distributions of plasma wave intensity in the inner magnetosphere using the long period observation datasets obtained by Akebono. This global mapping is useful not only in deriving the energy distribution of plasma waves but also energy transfer processes between wave and particle in the magnetosphere.
The wave above 1kHz in the vicinity of the outer radiation belt is dominantly chorus emission. The strongest chorus is observed in the dawn to noon sector. Our statistical study clarified that the wave intensity is enhanced in the recovery phase of magnetic storm. It is also found that higher frequency part of chorus distributes along smaller L-value and in earlier local time sector, and the projected map to the equatorial plane of the active region of chorus is possibly correspond with the region of injected energetic electrons. Direction finding method clarified that the chorus basically propagates along the same geomagnetic field line with a large wave normal angle. This result will be an important clue to understand a generation mechanism of relativistic electrons in the recovery phase of magnetic storm.
The ion composition of the ring current during quiet and disturbed periods. Measurements from the CRRES Spacecraft
A. Korth (Max-Planck-Institut fuer Aeronomie, Lindau, Germany; firstname.lastname@example.org), R.H.W. Friedel (Los Alamos National Laboratory, Los Alamos, NM, USA), F. Frutos (Max-Planck-Institut fuer Aeronomie, Lindau, Germany). A global view of the ring current composition is presented with data from the Combined Release and Radiation Effects Satellite (CRRES). We analyzed a comprehensive set of data using plasma ions, energetic electrons and ions (ion composition), electric field and magnetic field data. These data are ideal for investigating the interrelationship between the ring current strength as measured by Dst, the particles in the outer radiation belt, their effect on the global magnetic field and the convection effects caused by large electric fields. The abundance of ionospheric origin O+ is highly correleated with magnetic activity. During magnetic storms the O+ energy density exceeds the H+ energy density by up to an order of magnitude. The O+ ions are the main contributor to the ring current during the main phase of the storm. In the recovery phase the loss of H+ and O+ happens by charge exchange and escape of O+ through the magnetopause into the magnetosheath. An asymmetry is observed in the O+ ring current. The decay time for 100 keV ions is 10 times faster for O+ than for H+ ions for the charge exchange process. Therefore the O+ ring current is lost pretty fast.
Long Term Measurements of MeV Electrons by SAMPEX and Quantitative Prediction of MeV Electrons at Geostationary Orbit Using Solar Wind as the Only Input
Xinlin Li (LASP, Boulder, CO 80303; email: email@example.com), M. Temerin (SSL, U. of California, Berkeley, CA 94720), D. N. Baker (LASP, Boulder, CO 80303), S. G. Kanekal (LASP, Boulder, CO 80303), G. D. Reeves (MS D-466, LANL, Los Alamos, New Mexico, 87545), D. Larson (SSL, U. of California, Berkeley, CA 94720)
The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), a low-altitude and polar-orbiting satellite, has been measuring the outer radiation belt electron fluxes since its launch (July 3, 1992). The data provide a long-term global picture of the radiation belt electrons. The outer belt electrons show a great deal of variability on various time scales: a solar cycle, semi-annual (or seasonal), solar rotation time scales, and associated with magnetospheric storms. Since 1995 there have been almost continuous solar wind measurements from Wind (launched in late 1994) and ACE (launched in 1998). A new method of predicting relativistic electron fluxes at geostationary orbit based only on solar wind measurements has been developed. Using this method we have achieved a prediction efficiency of 0.81 and a linear correlation of 0.90 for the two years 1995 and 1996 for the logarithm of average daily flux of electrons with energies of 0.7-1.8 MeV. Using the model parameters based on the years 1995-1996, the prediction efficiency and the linear correlation for the entire five year period 1995-1999 are 0.59 and 0.80, respectively [Li et al., GRL, 2001]. The model is based on the standard radial diffusion equation, which was solved by making the diffusion coefficient a function of solar wind velocity and interplanetary magnetic field properties. The average lifetime of the electrons, however, was kept as a constant at a given location. Here we report that if we make the average lifetime of the electrons vary with the solar cycle such that the average lifetime is shorter during sunspot maximum (when the ionosphere is expanded), the prediction efficiency for the five year period 1995-1999 is enhanced to 0.62. We also report the prediction of higher energy electrons (1.8-3.5 MeV and 3.5-6.0 MeV) using the same model.
Multi-MeV ion injections into the inner magnetosphere associated with shocks and magnetic storms, based on observations from Polar, HEO, and SAMPEX
K. R. Lorentzen (firstname.lastname@example.org), J. E. Mazur, M. D. Looper, J. F. Fennell, and J. B. Blake (all at The Aerospace Corporation, Los Angeles, California, USA)
In association with several solar energetic particle events and large geomagnetic storms in 1998 and 2000, new 2-15 MeV proton radiation belts were formed at various locations between L=2.0 and L=3.5. We use observations from the Polar, highly elliptical orbit (HEO) 1997-068, and SAMPEX spacecraft to study details of the inner zone radiation belt at high and low altitudes. We focus specifically on the ISTP events of August 1998, September 1998, April 2000, and July 2000. During the July 2000 event, energetic helium and iron were also observed at L~2, suggesting a solar energetic particle source for these injected ions. We compare observations of these new belts and remark on the significant differences from event to event. The enhancements in protons are similar to enhancements in MeV electrons seen in the outer radiation belts, and we examine whether the same mechanisms could create increases in both electrons and protons.
On the Relationship Between Cross L-Shell Pc5 ULF Wave Power and Storm-Time Relativistic Electron Flux Enhancements in the Outer Radiation Belt
I. R. Mann (email@example.com), R. A. Mathie (both at Department of Physics, University of York, York, England) R. H. A. Iles and A. N. Fazakerley (both at Mullard Space Science Laboratory, University College London, Surrey, England)
Recent research has highlighted the possibility that large-amplitude ULF pulsations may act as an acceleration mechanism for generating relativistic electron populations in the outer zone magnetosphere during storm-time. We examine solar wind characteristics, Pc5 ULF wave power and outer magnetospheric measurements of high energy electron flux during the recurrent fast solar wind speed streams which occurred during the first half of 1995. We find a close correlation between extended intervals of significant pulsation power and GOES7 observations of enhanced relativistic (>2 MeV) electron flux in the outer zone magnetosphere, suggesting that these two features may be causally related. We demonstrate that significant electron flux increases at geosynchronous orbit are only observed in response to ULF wave power which is sustained at high levels over a number of days following storm onset. Further, using data from the STRV microsatellites, we examine the evolution of cross L-shell ULF wave power and relativistic (>750 keV) electron flux from L=3.75 to L=6.79. We find that in general, the fluxes in these fixed energy detectors rise across the whole of this L-shell range. In contrast, ULF wave power increases with increasing L-shell, and is typically an order of magnitude higher at L=6.6 than at L=4. Our observations suggest that ULF pulsations may be the likely acceleration mechanism for generating storm-time MeV ``killer'' electrons in the magnetosphere, and we discuss the implications of our observations for various proposed ULF wave-electron acceleration mechanisms.
X-ray Observations of Relativistic Electron Precipitation
R.M. Millan (Space Sciences Lab, U.C. Berkeley; firstname.lastname@example.org), K.R. Lorentzen (The Aerospace Corporation), R.P. Lin (Space Sciences Lab, U.C. Berkeley) and D.M. Smith (Space Sciences Lab, U.C.Berkeley)
The MAXIS (MeV Auroral X-ray Imaging and Spectroscopy) balloon experiment was launched on a long duration balloon from McMurdo, Antarctica on Jan. 12, 2000 carrying two hard X-ray imagers, a germanium spectrometer and a BGO scintillator. Seven x-ray bursts with significant flux extending above 0.8 MeV were detected during the 18 day flight. These events are characterized by an extremely flat spectrum (~E-1) indicating that the bulk of precipitating electrons producing the x-rays is at relativistic energies. The bursts were detected between magnetic latitudes 58-67(corresponding to L-values between 3.8-6.7) with durations varying from several minutes to several hours. The relativistic bursts were found to occur preferentially in the late afternoon/dusk sector (14:30-00:00 MLT) while softer precipitation was detected at all magnetic local times. From data obtained with the germanium spectrometer, we estimate the average flux of precipitating electrons with E greater than or equal to 0.8MeV to be ~100cm-2s-1 assuming bremsstrahlung production at 70km altitude. Assuming the events are distributed evenly over the range of magnetic latitudes, this corresponds to about 1025 precipitated electrons during the ten day observing interval and is comparable to the trapped fluxes suggested by Baker . The MAXIS observations thus suggest that these precipitation events may represent a significant loss of relativistic electrons.
Rebuilding of the outer radiation belt during the recurrent magnetic storms - Non-adiabatic acceleration by wave-particle interaction
Y. Miyoshi (Planetary Plasma & Atmospheric Research Center, Tohoku University, Japan; email@example.com) A. Morioka (Planetary Plasma and Atmospheric Research Center, Tohoku University, Japan) T. Obara (Communications Research Laboratory, Japan) T. Nagai (Tokyo Institute of Technology, Japan) Y. Kasahara (Kyoto University, Japan)
We have analyzed the data for energetic electrons and plasma waves from the EXOS-D and NOAA satellites, in order to seek the origin of the energetic electron flux enhancement during the recurrent storm recovery phase. The analysis showed that the outer belt electrons disappeared during the storm main phase, and reappeared and increased the intensity during the recovery phase.In the late main phase, the electron energy spectrum changed to hard and the phase space density increased with a significant peak structure in the inner portion of the outer radiation belt. The pitch angle distribution of enhanced electrons showed a pancake distribution. On the other hand, the intense whistler mode waves were generated just outside plasmapause, coinciding with the region where the electron energy spectrum changed to hard and the peak of the phase space density appeared. These results indicate the existence of the non-adiabatic acceleration process inside the outer radiation belt, and also suggest that the wave-particle interaction outside the plasmapause is a plausible candidate for the non-adiabatic acceleration.
The numerical analysis of the wave-particle interaction was performed, in order to verify whether the observed whistler mode waves could generate relativistic electrons. The simulation of the stochastic acceleration revealed the high-energy tail in the energy spectrum to be formed from the injected hot electrons with Maxwell energy distribution. The spatial and temporal variations of electron flux obtained by the numerical simulation are consistent with the observations. The simulated energy spectrum development is also consistent with the observed spectrum variation.
Magnetic field variations at geosynchronous orbit and its relations to relativistic electron flux during storm time
Tsutomu Nagatsuma and Takahiro Obara (Communications Research Laboratory 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795 JAPAN, firstname.lastname@example.org)
By doing a statistical analysis of the variation of the dipole tilt angle at geosynchronous orbit during storms, we found that the tail current significantly contributes to the magnetic field variation in the midnight sector. We, further, examined the drop out of the relativistic electrons and its relation to the magnetic field variations at geosynchronous orbit is controlled by the formation of the tail-like or stretched field in the night side sector. The stretched field can be made not only the development of storms (Dst) but also the enhancement of the dynamic pressure. And the mechanisms of the electron flux drop out during the storm time period are essentially the same with that during the growth phase of a substorm. The difference might be the magnitude and extent of the current system. Further, we found that drop out of the flux does not recover when the kappa, the square root of the ratio between curvature radius of magnetic field and particle gyroradius, is smaller than 5. This result suggests that the non-adiabatic pitch angle scattering is one of the important loss process for relativistic electron flux.
Correspondence Between Energetic Electron Events and the Parameters of the Near Earth Environment
T.P. O'Brien (email@example.com), R.L. McPherron, (both at IGPP, Univ. Calif. Los Angeles), G.D. Reeves, R. Friedel (both at Los Alamos National Laboratory)
We present general results showing what solar-terrestrial parameters are associated in a statistical sense with the appearance or absence of energetic electrons at geosynchronous orbit subsequent to magnetic storms. We have assembled an entire solar cycle worth of near Earth parameters. We combined this database with hourly geosynchronous and GPS equatorial energetic electron fluxes mapped to local noon. We examine the properties of storms that do and do not lead to energetic electron enhancements, and we examine which of those properties can themselves be used to anticipate which storms will produce energetic electrons. Finally, we present an empirical dynamic equation describing the hourly evolution of energetic electron flux at local noon, geosynchronous orbit, dependent on the local conditions.
Akebono Radiation Belt Map and Its Application for Space Weather
Takahiro Obara (Communications Research Lab.; T.Obara@crl.go.jp) Yoshizumi Miyoshi and Akira Morioka (PPARC, Tohoku Univ.)
In order to investigate global change in the Earth's radiation belts during the magnetic storms, we made radiation belt map based on 11 years of Akebono observations. The map, sorted by the storm phase, shows local time, radial and particle-energy dependence, and it provides some new things. The outer radiation belt connects inner radiation belt at the equatorial region. There is a clear local time dependence of the outer belt disappearance. The outer belt reappears, first, in the heart of the outer belt and in lower-energies, and then expands both inward and outward with time. Correlation with magnetic activities during the storm recovery phase demonstrates that the outer belt activated very much for the large magnetic activity. The radiation belt map also seems useful for the Space Weather Nowcast.
Nonadiabatic behaviour of particles near the dayside magnetopause
Kaan Ozturk (firstname.lastname@example.org), Anthony A. Chan, Richard A. Wolf (all at Department of Physics and Astronomy, Rice University, Houston, Texas, USA)
Near the magnetopause and local noon, magnetic field strength has a local maximum near the equatorial plane and two local minima to the north and south. Consequently, when a night-side particle which bounces symmetrically around the equator drifts toward noon, it may shift out of the equatorial plane and mirror about either the northern and southern polar cusp. Shabansky (1971) argued theoretically that particles following such trajectories in a static magnetic field will still conserve their first and second invariants from one orbit to the next, and their drift orbits will be periodic. However, our numerical particle traces in a simple magnetic field show that the second invariant is often not conserved from one orbit to the next and the drift path is then not periodic. The violation of the second invariant I occurs near the critical points where the particle shifts from mirroring about the equatorial plane to mirroring in the cusp region. We study this behaviour by following many guiding center trajectories. Each particle is followed for many drift periods to check the pattern of change in I. For particles that start with pitch angles close to 90 degrees, the evolution of I seems to be random.
Numerical Simulation of Steady State Proton, Positron, Isotope Ion Radiation Belts and of a Sudden Creation of Transient Helium Radiation Belt During Geomagnetic Storms
G. I. Pugacheva(1) (email@example.com), W. Gonzalez(1), A. A. Gusev(1), U. Jayanthi(1), I. M. Martin(2), D. Boscher(3), S. Bourdarier(3), W. N. Spjeldvik(4). (1) Instituto Nacional de Pesquisas Espaciais, INPE, Sao Jose dos Campos, SP 12201-970 , Brazil; (2) Instituto de Fisica, Universidade Estadual de Campinas, CP 6165, SP 13083-970, SP, Brazil; (3) ONERA/DESP - 2, Av. E. Belin, BP 4025, 31055 Toulouse Cedex4, France; (4) Weber State University, Department of Physics, Utah, Ogden, USA
We report the results of numerical solutions to the diffusive transport equation for energetic magnetospheric trapped protons, helium ions, and anti-particles. The governing equation for geomagnetically confined protons takes into account the deceleration of protons by Coulomb interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method (FEM) with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the kinetic energy range of 0.1-1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactory agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5-100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain due to uncertainties on boundary spectrum parameters or transport coefficients, unless they results from the NASA model also incorporating helium and oxygen ions rather than purely protons. In further work, we also considered the production of positron fluxes due to nuclear reactions in the Earth's magnetosphere, to simulate numerically the possible formation of a radiation belt populated with anti-electrons (positrons). In that work it is assumed that positrons and electrons are mainly produced in the decay of charged pions (pions - muons - electrons/positrons), which were produced in nuclear collisions of trapped relativistic inner zone protons with the residual atmosphere constituents at high altitudes. These positrons and electrons are immediately captured in the magnetosphere and create positron and electron radiation belts of purely nuclear reaction origin. We simulated the positron and electron trapped magnetospheric fluxes due to this source and obtained e+/e- flux ratios ~ 4. However, this positron excess would be absent when we considered source-protons of energies of the primary cosmic rays. The Alpha Magnetic Spectrometer (AMS) on board the space shuttle, in the equatorial region at altitudes of ; 400 km (i.e., The AMS collaboration, 2000), registered positron fluxes with flux intensities about 4 times higher than the electron fluxes at energies above 200 MeV. This agreement between the e+/e- flux ratio calculated due to the nuclear collisions of the trapped protons and the AMS positron and electron observations is significant. Furthermore, our modeling of nuclear spallation reactions show production of light element isotopes of D, T, 3He and 4He, and we found especially significant the generated excess of 3He over 4He fluxes. The AMS instrument also looked at the isotopic distribution of helium nuclei and only 3He was observed, and that observed fact additionally favors our hypothesis of the nuclear interactions of trapped protons with residual atmosphere in the production of positrons and light element isotopes. We also attempted to reproduce the characteristics of the observed sudden increase in deep inner zone particle fluxes by computational modeling using a three dimensional charged particle transport code. In this regard, measurements from the CRRES spacecraft had shown the sudden formation of three additional radiation belts of >10 MeV electrons, of >30 MeV protons, and of several MeV helium ion fluxes, all on a rather short time scale of less than a drift time period around the Earth. In the present work we used a version of the multi-dimensional Salammbo-code for Helium ions, and we show that two simultaneous events:  solar energetic particles arriving in the vicinity of the Earth; and  an intense geomagnetic storm can lead to a build-up of a new Helium belt over a wide energy range even well inside the classical charged particle trapping region. For parameters corresponding to the March 1991 geomagnetic storm we can reproduce a helium transient radiation belt at L~3 over a time span of hours after beginning of the storm. The presentation will highlight direct comparison between theory and experiment.
Early Results from the Compact Environmental Anomaly Sensor (CEASE) on TSX-5
Kevin Ray (Kevin.Ray2@Hanscom.af.mil), Wallace Turnbull, Don Brautigam, Bronislaw Dichter (all at Air Force Research Laboratory, USA), and Robert Redus (Amptek Inc., USA).
The Compact Environmental Anomaly Sensor (CEASE) was launched on-board the USAF Space Test Program (STP) Tri-Service Experiment-5 (TSX-5) satellite on June 7, 2000 into a 410 X 1710 km orbit with a 70 degree inclination. CEASE is a small (10 X 10 X 8.2 cm3), low-power (1.5 W), low-mass (1 kg) instrument that measures the local space radiation environment and generates warnings of radiation damage, dielectric charging, and single event effects (SEE). CEASE uses a complement of five silicon, solid-state sensors to measure the radiation environment: two independent dosimeter detectors, a two-element energetic particle telescope, and an SEE detector.
The low-earth, highly inclined orbit is ideal for demonstrating the instrument's capabilities. Apogee occurs in the inner proton belt, perigee occurs in a very benign environment, and the high inclination portions of the trajectory pass through the auroral oval and the horns of the outer electron belt. Initial flight data including measurements made during the Bastille Day storm and its interpretation will be presented. Comparisons between flight data and predicted dose data from radiation belt models will be presented.
Observations of Relativistic Electron Coherence as a Function of Energy, L-Shell, and Pitch Angle
G. D. Reeves (firstname.lastname@example.org), R. H. W. Friedel, K. L. McAdams, and T. E. Cayton (all at Los Alamos National Laboratory, Los Alamos, NM, USA)
Observations of relativistic electrons in the outer radiation belt made by multiple satellites in different orbits typically show very good agreement with one another in spite of the fact that the measurements sample different ranges of the equatorial pitch angle distribution. Several authors [e.g. Kanekal et al., 1999] have discussed this remarkable coherence and its implications for relativistic electron acceleration and dynamics, particularly with respect to pitch angle diffusion rates. The nature and extend to which the radiation belts are coherent is important for several reasons. From the perspective of basic physical understanding it has relevance to the investigation of acceleration, transport, and loss processes. From the perspective of space weather applications it has relevance to the construction of models and to the extrapolation of measurements from their point of observation to other regions or satellites of interest which may not have environmental monitors. The established coherence of relativistic electron dynamics is a useful characteristic but it does not apply to all aspects of radiation belt dynamics or under all conditions. For example, it has been noted that the changes in relativistic electron fluxes measured at different L-shells (e.g. L=6.6 vs. L=4.2) can be quite different. Likewise relativistic electron events can look quite different at different energies. We have also found that, for at least some events and some time scales, the fluxes at different equatorial pitch angles can have different time profiles even when gross characteristics appear quite coherent. Here we further examine the coherence of the outer radiation electron belt population and investigate the exceptions to the overall coherence in order to assess the implications for proposed physical processes and for space weather applications.
Determining the size of lightning-induced electron precipitation patches
Mark A. Clilverd (Physical Sciences Division, British Antarctic Survey, Cambridge, England), Craig J. Rodger (Low Frequency Electromagnetic Research Ltd., Dunedin, New Zealand; email: email@example.com), David Nunn (University of Southampton, Southampton, England), Richard L. Dowden (Low Frequency Electromagnetic Research Ltd., Dunedin, New Zealand)
We analyse perturbations (known as ``Trimpi'' perturbations) on VLF transmissions due the precipitation of radiation belt electrons into the Earth-ionosphere waveguide. Trimpi signatures are examined during 23 and 24 April 1994 at 4 sites on or near the Antarctic Peninsula (Palmer, Faraday, Rothera, and Halley) on subionospheric VLF signals received from 4 US naval transmitters (NAA, NSS, NLK and NPM). Electron precipitation patches are found to be large i.e. at least 1500 km X 600 km, with the longer axis orientated east-west. Calculations using a 3-D Born scattering model provides results which are consistent with this picture, where patch densities are 2 el cm-3 above ambient at the center, at about 84 km altitude. A high proportion (38%) of the Trimpi events were associated with strong lightning flashes in Eastern USA. When lightning discharges had currents >65 kA (positive or negative) there was a >80% chance of seeing an associated Trimpi event. The chance of seeing any Trimpi events fell to near-zero for discharges of <45 kA. The largest Trimpi perturbations occur when the center of the precipitation patch is 700-800 km from the receivers. This result is consistent with the modelling calculations for large patches. The equatorwards edge of the precipitation patch was estimated to be at about 60°S, close to the magnetic conjugate of the lightning. The close association of the equatorwards edge of the precipitation patch with the conjugate location of the causative lightning is consistent with a quasi-ducted mechanism. Nonducted whistler precipitation mechanisms would predict a 5-10°latitudinal gap between the lightning and the equatorwards edge of the patch. However, the lack of observed whistlers at the time of the Trimpi events is consistent with the nonducted whistler mechanism and is not consistent with the quasi-ducted mechanism, although the distances from duct exit point to receiver may have been too large (~700-1000 km) for the signals to propagate clearly. Using the significantly larger patch dimensions determined in this study it is estimated that lightning may well be 10-100 times more effective at depleting the radiation belts than hiss.
The role of ULF and VLF waves on non-adiabatic radiation belt dynamics during storms
Richard M. Thorne (Department of Atmospheric Sciences, UCLA; firstname.lastname@example.org)
The adiabatic treatment of energetic radiation belt electrons becomes invalid during geomagnetically disturbed periods. Enhanced levels of ULF waves (periods of minutes) can violate the third adiabatic invariant during a magnetic storm. This generally leads to rapid inward radial diffusion and a concomitant energization, as long as the first invariant is approximately conserved during the inward transport. However, the injection of plasmasheet particles into the outer radiation belt during a storm, provides a source of free energy for the excitation of VLF waves. Such waves are also able to interact with the high-energy electron population causing first invariant violation, which leads to both pitch-angle scattering and energy diffusion. Resonant interactions between stormtime VLF waves and relativistic electrons can induce rapid precipitation loss to the atmosphere and local stochastic acceleration, leading to a hardening of the energy spectra during the storm recovery. Such VLF resonant processes provide important constraints on the acceleration of electrons to relativistic energies that may account for the widely varied response during different magnetic storms.
Magnetic field models for studying radiation belt dynamics
Frank Toffoletto (Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA; email@example.com)
This presentation reviews the use of magnetic field models in studying radiation belt dynamics. While all such models need to be quantitative and global in scope, other requirements vary depending on the type of study being done. For example, particle-tracing studies require a mutually consistent specification of not only the magnetic field vector, but also of the convection electric field vector. Full-particle traces require, additionally, that the computational algorithm be quick and efficient. This presentation examines three classes of magnetic field models: (1) empirical, (2) global MHD, and (3) fully theoretical. The advantages and appropriateness of each class of model are discussed.
Results of Radiation Monitoring on the International Space Station and Associated Biological Risks
Mark Weyland (Lockheed Martin - Johnson Space Center, Houston, TX 77058, USA; firstname.lastname@example.org), Edward Semones (Lockheed Martin - Johnson Space Center, Houston, TX 77058, USA) and Mike Golightly (NASA Johnson Space Center, Houston, TX 77058, USA)
The radiation exposure on board the International Space Station (ISS) has been measured since May 1999 with thermo luminescent dosimeters (TLDs). We will discuss measurements taken at three locations in the US built Node 1 and four locations in the Russian built Service Module, and preliminary results from the US Lab module. Routine measurements taken aboard the Space Shuttle during four separate missions that installed/exchanged the ISS dosimeters will also be discussed. The ISS area measurements also overlap with ISS crew personal dosimeter measurements and provide an early estimate of crew-absorbed dose. The potential short and long term health risks from these exposures will also be discussed. The current results show dose rates ranging from 0.19 mGy/d to 0.30 mGy/d in Node 1 and 0.14 mGy/d to 0.20 mGy/d in the Service Module.
Global MHD simulations of Magnetic Storms Driven by Magnetic Clouds
M. Wiltberger (email@example.com), M. K. Hudson and J. G. Lyon (all at Dartmouth College, USA)
Global magnetohydrodynamic simulations provide a unique perspective on the transfer of energy and momentum from the solar wind into the magnetosphere. In this paper we present results from the Lyon-Fedder-Mobarry global MHD simulations for magnetic storms. In particular we will concentrate on storms which are driven by magnetic clouds since these structures are easily identifiable in the solar wind and are associated with up to 50% of major magnetic storms. Furthermore, the simple structure of these clouds allows us to create idealized solar wind configurations which can be used to assist in isolating important aspects of the cloud profile that control geoeffectiveness. We will present results from a series of actual storm events and quantify their geoeffectiveness by monitoring the cross polar cap potential, the location of the dayside magnetopause, and energization of radiation belt electrons. We will also comment on the role of magnetic cloud polarity on geoeffectiveness by rerunning these storms with opposite cloud polarity. Idealized cloud configurations will be used to determine the relationship between solar wind speed and cloud duration on geoeffectiveness by constructing solar wind conditions which input the same about amount of energy over different lengths of time. In addition, we will present the results from a Fourier analysis of the ULF wave structure during these idealized clouds to further understand the role ULF waves in energizing radiation belt electrons.
How to avoid effects of space weather on satellites - a Tsunami initiative
Norma B. Crosby (1) (firstname.lastname@example.org), Andrew J. Coates (1), Richard B. Horne (2), Mervyn P. Freeman (2). (1) University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK. (2) British Antarctic Survey, Madingley Road, Cambridge CB3 0ET, UK.
Mullard Space Science Laboratory is conducting two studies, that are partly being funded by the satellite insurance industry, as part of the Tsunami initiative, to examine the effects of space weather on satellites. The first study involves the development of a ``black box'' detector to be carried by future commercial satellites. This will add much needed data to what are currently sparse records of the radiation environment near the Earth. The second study which is a joint effort with the British Antarctic Survey involves the categorisation of the magnetospheric environment at times of satellite anomalies. This will pave the way for early work on predicting periods that may be hazardous to satellites. Here we describe the second study.
Simulation of Enhanced Storm-Time Radial Diffusion of Relativistic Electrons
Yue Fei (email@example.com), Anthony A. Chan (both in the Department of Physics and Astronomy, Rice University, Houston, Texas, USA), and Scot R. Elkington (Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA).
Transport of relativistic electrons in the radiation belts can be modeled using the three adiabatic invariants as phase-space coordinates. If the first and second adiabatic invariants are conserved the motion may be modeled with a radial diffusion equation. By numerically solving the radial diffusion equation, we compare the effect of time-dependent internal and external sources. We also calculate solutions using an AE8MIN phase space density initial condition and a ULF wave diffusion coefficient. Results compared to MHD-particle simulations of the September 1998 storm will be presented. Early results shows similarities between the phase-space densities calculated by the two methods but also differences which indicate that in solving the radial diffusion equation a dynamic outer boundary corresponding to the dynamic magnetopause location is needed.
The Applied Models of the Earth Radiation Belts
Panasyuk M.I., Getselev I.V. (email: firstname.lastname@example.org), Krasotkin S.A. (all at Scobeltsin Institute of Nuclear Physics, Moscow State University 119899, Moscow, Russia)
The application problems of the Earth radiation belts (ERB) wide-known models are discussed. We conclude that in the cosmonautics practice on the whole the ERB models are used to obtain the ionizing radiation characteristics which are necessary to provide the space flights radiation safety. The difficulties of the current ERB models (including standardized ones) application are mentioned. The new ways of the creation of ERB special models are discussed. These models are to be adopted in the optimal way for their use at the particular stages of space system life.
The Methods of the Estimations of the Radiation Conditions for the Earth Artificial Satellites
Getselev I.V. (email@example.com), Krasotkin S.A. (both at Scobeltsin Institute of Nuclear Physics, Moscow State University 119899, Moscow, Russia)
The applied methods used for of the estimation of the radiation conditions for the Earth artificial satellites (EAS) are discussed. The necessity for the special adaptations of the current models for this purpose is stressed. These models include the space ionizing radiation model, the Earth magnetic field model and the methods of the calculation of the spacecraft trajectory in the geographic and (L,B) coordinates. The optimal calculation methods of the radiation conditions onboard the spacecraft are proposed. We recommend to create the particular model for each particular orbit. These models are to contain the information about the particle fluxes and radiation doses outside and inside the EAS. For the current orbits the particular models are to be based on the data directly achieved onboard the EAS.
The Solar Cosmic Rays Normative Models
Getselev I.V. (firstname.lastname@example.org), Krasotkin S.A. (both at Scobeltsin Institute of Nuclear Physics, Moscow State University 119899, Moscow, Russia)
The requirements for the solar cosmic rays (SCR) normative models are formalized. These normative models are intended to be utilized at the stages of the spacecraft's designing and manufacturing to provide the space flight radiation safety. The application for these purposes of the current SCR models and the ways of the creation and development of the new ones are discussed. We conclude that the it is useful to base the normative models on the statistical analysis of the galactic cosmic rays annual fluences.
Twenty Years of Radiation Measurements in Low-Earth Orbit: What Have We Learned Space Radiation Environment?
M.J. Golightly (email: email@example.com) (1), M.D. Weyland (2), A.S. Johnson (2), and E. Semones (2). (1) NASA Johnson Space Center, Houston, TX 77058; (2) Lockheed Martin-NASA Johnson Space Center, Houston, TX 77058.
The advent of the Space Shuttle program has made possible space radiation environment measurements spanning a wide range of altitudes and orbital inclinations over multiple solar cycles. These measurements range from routine integral dose measurements with thermoluminescent dosimeters to particle energy spectra measurements made with a charged particle telescope. This paper will review the new understanding about the space radiation environment gained from this diverse data set. Major findings from these measurements include: estimations of the westward drift rate of the South Atlantic Anomaly (SAA) of 0.28-0.49°/y; evidence for a northward component to the SAA drift of 0.08-0.12°/y; observation of the formation and decay of the pseudo-stable additional radiation belt following the Mar 1991 SPE and geomagnetic storm with an estimated decay e-folding time of 9-10 months; observation of a local geomagnetic east-west trapped proton exposure anisotropy with an estimated magnitude of 1.6-3.3; demonstration that the trapped proton exposure in low-Earth orbit (LEO) can be reasonably modeled as a power law function of atmospheric density in the SAA region, with best correlations obtained when the exospheric temperature saturates at 938-975 K; the actual solar cycle modulation of trapped proton exposure in LEO is less than predicted by the AP8 model; and the testing and validation of GCR flux models, radiation transport codes, and dynamic geomagnetic cutoff models. Long-term, time-resolved proportional counter measurements made aboard the Mir during the same period provides further demonstration of the solar cycle modulation of the trapped protons at low altitudes; the observed modulation is also well described as power law function of atmospheric density.
These data and findings have helped to improve the overall accuracy of pre-mission crew exposure projections using various semi-empirical space environment models, radiation transport codes, and spacecraft radiation shielding models. During the rise phase of solar cycle 22 (1987-1991), the RMS error between preflight exposure projections and measured crew exposure was 73%. For the rise phase of cycle 23 (1997-2001), the preflight exposure projection RMS error has decreased to 23%.
The launch and assembly of the Space Station has begun a new era of long-term LEO space environment monitoring. The radiation environment at the Space Station will be monitored with three external charged particle telescopes oriented in the velocity vector, anti-velocity vector, and zenith directions. Data from the telescopes will provide charge, mass, energy, and arrival direction for incident particles with energy to mass ratios of 13-450 MeV/amu and Z of 1-24. The external environment data will be complimented by measurements from a portable charged particle telescope and proportional counter located inside the vehicle.
New Evidences of Space Weather Impact on Weather and Climate in Southern Hemisphere
A. Gusev(1) (firstname.lastname@example.org), A. Almeida(2), I. M. Martin(2), G. Pugacheva(1,2), V. M. Pankov(3), and W. N. Spjeldvik(4). (1) Instituto Nacional de Pesquisas Espaciais, INPE, São José dos Campos, SP, Brazil; (2) Instituto de Fisica, University of Campinas, SP, Brazil; (3) Space Research Institute of Russian Academy Science, Moscow, Russia; (4) Department of Physics, Weber State University, Ogden, UT 84408, USA
Data on liquid precipitation in Brazil for three meteorological stations (Pelotas: 31°45'S, 52°21'W; Campinas: 22° 53'S, 47°04'W; Fortaleza: 3°45'S, 38° 31'W) covering all latitudinal range of Brazil from 1849 up to 2000 were considered. Periodic analysis of the annual rainfall level shows a pronounced 22-year periodicity for several littoral regions. The amplitude of the variation reaches <<~90%. The best correlation with a 22-year solar magnetic field cycle is obtained with the assumption that the phase of the correlation is changed once during the whole 150 years of observations at Fortaleza and during the 100 year's observations at Pelotas. In Fortaleza correlation coefficients are -77% +/- 4% during 1849-1940 and +80.0 +/- 4% during 1952-2000 and in Pelotas 60% +/- 13% in 1893-1920 and -84% +/- 4% from 1929 up to 2000 reaching even more than 90% during the time intervals (1928-1939; 1948-1959; 1970-1981) when IMF was positive. The phase of the correlation is different and even opposite for various regions. The phase change occurred mostly during even 16th and 18th solar cycles, first at higher latitudes, later in the equatorial region. The rainfall series also demonstrate of about 50% correlation with a 24-year periodicity probably connected with the atmosphere-ocean coupling and without suggestion about phase change. Analysis of short-term rainfall variations shows a significant increase in rainfall level several days after magnetic sector boundary (MSB) crossing. It is an argument in favor of existence of physical link between rainfall variations and solar magnetic cycle. The results appear to have bearing both as a scientific instrument for the solution of the sun-weather connection problem and possibly for long term and short term practical forecasting in the South American region and elsewhere.
Identification of Satellite Anomalies Associated with Magnetic Storms Using Statistical Methods
Richard B. Horne (R.Horne@bas.ac.uk), Mervyn P. Freeman, Matthew Daws and Kathleen Rutten (British Antarctic Survey, Cambridge, England).
Rapid variations in the relativistic electron flux are often observed in association with magnetic storms. In fact it has been shown that more than 90% of storms are associated with flux enhancements in the outer radiation belt to levels far greater than the pre-storm level [Reeves, 1998]. Here we show that it is very difficult to identify the cause of satellite anomalies unambiguously by inspection of individual storm events since there are so many variable factors involved. Instead we present a statistical method to find the proportion of satellite anomalies that are associated with magnetic storms. The method is valid provided magnetic storms occur randomly. This restricts the analysis to storms of type moderate and stronger (minimum Dst < -50 nT). The method does not require anomalies to be recorded continuously, but does require more than 300 anomalies to yield statistically significant results. Using anomaly datasets from NOAA and ESA, we show that for some spacecraft up to 25% of all the recorded anomalies can be related to magnetic storms.
A Model-Study on Terrestrial Synchrotron Radiation Flux: Variability and Possibility of Detection
Hiroaki Misawa (email: email@example.com) Akira Morioka, Yoshizumi Miyoshi (all at Planet. Plasma Atmos. Res. Cent., Tohoku Univ., Japan)
Several kinds of MHz-range terrestrial radio events have been reported by mainly ground-based observations as 'strange' events because the generation mechanism(s) has(have) been still unspecified. One of plausible candidates of the mechanism is synchrotron radiation process of relativistic electrons, however, quantitative flux evaluations have not been well performed so far as to confirm whether the process is suitable for the source of radio events. We have made a model-study on terrestrial synchrotron radiation flux to investigate characteristic variations in time and space domain and where and which case of physical conditions the radiation can be detected. We report method of the modeling and preliminary results.
Dynamics of energetic particles in the inner radiation belt during magnetic storms
A. Morioka, Y. Miyoshi (email: firstname.lastname@example.org), (both at Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai, 980-8578, Japan, phone +81-217-6737), T. Obara (Communication Research Laboratory, Koganei, Tokyo, 184-8795, Japan)
The relation between energetic particles in the inner radiation belt and magnetic storms is investigated using the NOAA12 and Akebono satellite data. The present analysis disclosed that the proton enhancement during the main phase of a magnetic storm, in the energy range from 30 - 80 keV occurs deep in the inner belt almost simultaneously with the increase in the outer magnetosphere, and its lower boundary is less than L = 2. The time profile of the proton flux variation is quit similar to that of Dst. These suggest that the ring current protons are injected not only in the outer region but also into the inner region of the radiation belt. We suppose that the induced electric field by the ring current variation may be the cause of the proton acceleration in the inner region. Electron spikes in the energy range from 30 to 300 keV are also detected in the inner radiation belt during the main phase of the magnetic storm. The flux increases up to 10 times with the duration of less than 1 day. This impulsive enhancement (electron spike) is synchronized with the onset of the outer belt electron decrease, but not caused by the transport or injection process from the outer belt, indicating the existence of the independent acceleration process.
A model of outer radiation belt electron dynamics during the November 1993 magnetic storm
S. Naehr and R. A. Wolf (Department of Physics and Astronomy, Rice University, Houston, Texas, USA; email@example.com), G. D. Reeves and T. Cayton (Los Alamos National Laboratory, Los Alamos, New Mexico, USA)
A computer model has been built to simulate the dynamic evolution of outer radiation belt electrons. The model calculates changes in flux due to three mechanisms: (1) fully-adiabatic response of electrons to variations in the magnetic field, (2) time-dependent radial diffusion, parameterized by Kp, and (3) penetration of new particles into the model via a time-dependent outer boundary condition. Data from Los Alamos geosynchronous satellites, the CRRESELE statistical electron flux model, the Kp index, and the Rice Field Model are used to provide realistic, time-dependent inputs to the model. To evaluate the model, a simulation of the radiation belts during the November 3-12, 1993 magnetic storm was generated. Comparision of results to Global Positioning System (GPS) radiation dosimeter data indicates that the model can accurately predict storm-time flux variations for electrons with energies less than 600 keV. Modeled fluxes for higher energy electrons show insufficient enhancement during the recovery phase of the storm, suggesting the existence of an additional acceleration mechanism within the radiation belts.
Fitting Seasonal Variations and Solar Cycle Dependence on SAMPEX/PET Trapped Proton Data
D. Heynderickx (D.Heynderickx@oma.be), M. Kruglanski (both at Belgisch Instituut voor Ruimte-Aëronomie, B-1180 Brussel, Belgium), M. D. Looper, J. B. Blake (both at the Aerospace Corp., Los Angeles, CA, USA). Presented by B. Quaghebeur (Belgisch Instituut voor Ruimte-Aëronomie, B-1180 Brussel, Belgium).
The low-altitude trapped proton population exhibits strong time variations related to geomagnetic secular variation and neutral atmosphere conditions. The flux measurements of the Proton Electron Telescope (PET) onboard the polar satellite SAMPEX constitute an adequate data set to distinguish different time scales and to characterise the respective variations. Four years of data have been analysed up to now; the data from 1996 up to the present are now being processed. The flux measurements have been binned, for each energy channel, over a coordinate grid in K,hminspace, where Kaufmann's K = I sqrt(B) replaces the traditional McIlwain L value, and hmin is the minimum altitude on the particle drift shells. We opted for these coordinates as they take into account the secular variation of the geomagnetic field and the movement of the dipole centre with respect to the Earth's centre of mass.
Running flux averages have been made over one month intervals. In order to separate the seasonal variation in the data from the solar cycle variation, the averages corresponding to the same month in successive years were fitted to the F10.7 solar radio flux. The resulting fit parameters for each month of the year were in turn fitted to a sine curve. In this way, the full time resolution of the data is modelled by a limited number of parameters per coordinate bin and energy channels. For the four years of data currently available, we are limited to a linear fit in F10.7. When the remaining five years of data are added, a parabolic fit will be used, which is more suitable.
Radiation environment and effect models and tools in SPENVIS
D. Heynderickx (D.Heynderickx@oma.be), B. Quaghebeur and E. Speelman (Belgisch Instituut voor Ruimte-Aëronomie, B-1180 Brussel, Belgium) H.D.R. Evans, E.J. Daly (ESA Space Environment and Effects Analysis Section, Keplerlaan 1, NL-2200 AG Noordwijk, The Netherlands)
The ESA SPace ENVironment Information System (SPENVIS) provides standardized access to models of the hazardous space environment through a user-friendly WWW interface. The interface includes parameter input with extensive defaulting, definition of user environments, streamlined production of results (both in graphical and textual form), background information, and on-line help. It is available on-line at http://www.spenvis.oma.be/spenvis/. Intranet versions are also available.
SPENVIS is based on internationally recognised standard models and methods in many domains. It uses an ESA-developed orbit generator to produce orbital point files necessary for many different types of problem. It has various reporting and graphical utilities, and extensive help facilities. SPENVIS includes models of the radiation environment and effects, including NIEL and internal charging. It also contains an active, integrated version of the ECSS Space Environment Standard, and access to in-flight data. Apart from radiation and plasma environments, SPENVIS includes meteoroid and debris models, atmospheric models (including atomic oxygen), and magnetic field models.
The SPENVIS radiation module features models of the proton and electron radiation belts, as well as solar energetic particle and cosmic ray models. The particle spectra serve as input to models of ionising dose (SHIELDOSE), Non-Ionising Energy Loss (NIEL), and Single Event Upsets (CREME). Material shielding is taken into account for all these models, either as a set of user-defined shielding thicknesses, or in combination with a sectoring analysis that produces a shielding distribution from a geometric description of the satellite system. A sequence of models, from orbit generator to folding dose curves with a shielding distribution, can now be run as one process, which minimizes user interaction and facilitates multiple runs with different orbital or shielding configurations.
Spacecraft Charging Models in ESA's SPace ENVironment System (SPENVIS)
D. Heynderickx, B. Quaghebeur (Bart.Quaghebeur@oma.be), E. Speelman (all at Belgian Institute for Space Aeronomy), H.D.R. Evans, E.J. Daly (ESA Space Environmental Effects Analysis Section)
The ESA SPace ENVironment Information System (SPENVIS) provides standardized access to models of the hazardous space environment through a user-friendly WWW interface. The interface includes parameter input with extensive defaulting, definition of user environments, streamlined production of results (both in graphical and textual form), background information, and on-line help. The system can be accessed at the WWW site http://www.spenvis.oma.be/spenvis/. Intranet versions are also available. The results of a SPENVIS model run are presented in the form of reports and data files that can be downloaded by the user, and as a variety of plot types (line plots, maps and 3-D plots) in different graphics formats (GIF, PS, JPG, VRML, ...). Extensive help facilities are provided in SPENVIS: context-sensitive help pages provide information on the model parameters and usage, background pages contain in-depth material on the space environment and models, and a user guide and links to other sites are available as well. SPENVIS features a number of models and tools for evaluating spacecraft charging. The DERA DICTAT tool for evaluation of internal charging calculates the electron current that passes through a conductive shield and becomes deposited inside a dielectric, and predicts whether an electrostatic discharge will occur. SPENVIS has implemented the DERA EQUIPOT non-geometrical tool for assessing material susceptibility to charging in typical orbital environments, including polar and GEO environments. SPENVIS Also includes SOLARC, for assessment of the current collection and the floating potential of solar arrays in LEO. Finally, the system features access to data from surface charging events on CRRES and the Russian Gorizont spacecraft, in the form of spectrograms and double Maxwellian fit parameters.
AF-GEOSpace: Energetic Particle Radiation Environment Model Platform
Kevin P. Ray (Kevin.Ray2@hanscom.af.mil), Robert V. Hilmer, Donald H. Brautigam, and Gregory P. Ginet (all at Air Force Research Laboratory, Space Vehicles Directorate (AFRL/VSBX))
The AF-GEOSpace space environment software program supplies information crucial to the design, operation, and simulation of a wide variety of communications, navigation, and surveillance systems. Environmental effects range from intermittent navigation or communication outages caused by ionospheric scintillation to satellite system failures caused by intense fluxes of magnetospheric particles. AFRL designed the AF-GEOSpace code to facilitate the assessment or simulation of such effects by incorporating often-used climatological, real-time specification, and forecast models of the space environment into a single user-friendly and graphics intensive master program. Particularly relevant for this Radiation Belt workshop are the following science and application modules: APEXRAD (APEX radiation dose model), CHIME (CRRES/SPACERAD Heavy Ion Model of the Environment), CRRESPRO and CRRESELE (CRRES proton and electron flux models), CRRESRAD (CRRES radiation dose model), LET-APP (Linear energy transfer spectrum calculator based on CHIME and CRRESPRO environments), and SEEMAPS (contour maps of relative probability for Single Event Effects based on APEX and CRRES data). The status of new radiation models being developed for AF-GEOSpace, including those based on recently acquired data from the Compact Environment Anomaly Sensor (CEASE), will be presented.
Common input data sets, application modules (e.g., orbit and link generation), and visualization tools (e.g., radar fans) provided to all models via the open software architecture become the back-bone of this integrated space environment tool. Consequently, AF-GEOSpace serves as platform for rapid prototyping of operational products, scientific model validation, environment specification for spacecraft design, mission planning, and anomaly resolution.
AF-GEOSpace is distributed by The Space Weather Center of Excellence at the Air Force Research Laboratory (http://www-vsbs.plh.af.mil/). To obtain AF-GEOSpace, please contact the second author.
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