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R S Selesnick - One of the best experts on this subject based on the ideXlab platform.
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simulations of Inner Radiation Belt proton loss during geomagnetic storms
Journal of Geophysical Research, 2015Co-Authors: M Engel, B T Kress, M K Hudson, R S SelesnickAbstract:The loss of protons in the outer part of the Inner Radiation Belt (L = 2 to 3) during the 6 April 2000 solar energetic particles event has been investigated using test particle simulations that follow full Lorentz trajectories with both magnetic and electric fields calculated from an empirical model. The electric fields are calculated as inductive fields generated by the time-changing magnetic field, which is achieved by time stepping analytic magnetic fields. The simulation results are compared with proton measurements from the highly elliptical orbit satellite for three different energy ranges (8.5–35 MeV, 16–40 MeV, and 27–45 MeV) as well as previous modeling work done. In previous work, Inner zone Radiation Belt loss during geomagnetic storms has been modeled by simulating field line curvature scattering in static magnetic field snapshots with no electric field. The inclusion of the inductive electric field causes an increase in loss to lower L shells, improving the agreement with the satellite data.
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measurement of Inner Radiation Belt electrons with kinetic energy above 1 mev
Journal of Geophysical Research, 2015Co-Authors: R S SelesnickAbstract:Data from the Proton-Electron Telescope on the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, taken during 1992–2009, are analyzed for evidence of Inner Radiation Belt electrons with kinetic energy E > 1 MeV. It is found that most of the data from a detector combination with a nominal energy threshold of 1 MeV were, in fact, caused by a chance coincidence response to lower energy electrons or high-energy protons. In particular, there was no detection of Inner Belt or slot region electrons above 1 MeV following the 2003 Halloween storm injection, though they may have been present. However, by restricting data to a less-stable, low-altitude trapping region, a persistent presence of Inner Belt electrons in the energy range 1 to 1.6 MeV is demonstrated. Their soft, exponential energy spectra are consistent with extrapolation of lower energy measurements.
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high energy Radiation Belt electrons from crand
Journal of Geophysical Research, 2015Co-Authors: R S SelesnickAbstract:A calculation of the Inner Radiation Belt electron source from cosmic ray albedo neutron decay (CRAND) is described. High-energy electrons are included by Lorentz-transforming the β decay spectrum from the neutron rest frame to the Earth's rest frame and combining with the known high-energy albedo neutron energy spectrum. Balancing the electron source with energy loss to atmospheric neutral atoms and plasma, and with a decay lifetime representative of plasma wave scattering, then provides an estimate of trapped electron intensity. It is well below measured values for low energies, confirming that CRAND is not a significant source of those trapped electrons. For kinetic energies above the maximum β decay energy (E > 0.8 MeV) a power law energy spectrum ∼E−4 is predicted. For L = 1.5 and E≳2 MeV the computed omnidirectional trapped electron intensity exceeds an extrapolation of the measured low-energy exponential energy spectrum.
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upper limit on the Inner Radiation Belt mev electron intensity
Journal of Geophysical Research, 2015Co-Authors: R S Selesnick, Shrikanth G. Kanekal, D N Baker, A N Jaynes, J F Fennell, Q Schiller, L W Blum, J B BlakeAbstract:No instruments in the Inner Radiation Belt are immune from the unforgiving penetration of the highly energetic protons (tens of MeV to GeV). The Inner Belt proton flux level, however, is relatively stable; thus, for any given instrument, the proton contamination often leads to a certain background noise. Measurements from the Relativistic Electron and Proton Telescope integrated little experiment on board Colorado Student Space Weather Experiment CubeSat, in a low Earth orbit, clearly demonstrate that there exist sub-MeV electrons in the Inner Belt because their flux level is orders of magnitude higher than the background, while higher-energy electron (>1.6 MeV) measurements cannot be distinguished from the background. Detailed analysis of high-quality measurements from the Relativistic Electron and Proton Telescope on board Van Allen Probes, in a geo-transfer-like orbit, provides, for the first time, quantified upper limits on MeV electron fluxes in various energy ranges in the Inner Belt. These upper limits are rather different from flux levels in the AE8 and AE9 models, which were developed based on older data sources. For 1.7, 2.5, and 3.3 MeV electrons, the upper limits are about 1 order of magnitude lower than predicted model fluxes. The implication of this difference is profound in that unless there are extreme solar wind conditions, which have not happened yet since the launch of Van Allen Probes, significant enhancements of MeV electrons do not occur in the Inner Belt even though such enhancements are commonly seen in the outer Belt.
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observations of the Inner Radiation Belt crand and trapped solar protons
Journal of Geophysical Research, 2014Co-Authors: R S Selesnick, Shrikanth G. Kanekal, D N Baker, M K Hudson, A N Jaynes, B T KressAbstract:Measurements of Inner Radiation Belt protons have been made by the Van Allen Probes Relativistic Electron-Proton Telescopes as a function of kinetic energy (24 to 76 MeV), equatorial pitch angle, and magnetic L shell, during late 2013 and early 2014. A probabilistic data analysis method reduces background from contamination by higher-energy protons. Resulting proton intensities are compared to predictions of a theoretical Radiation Belt model. Then trapped protons originating both from cosmic ray albedo neutron decay (CRAND) and from trapping of solar protons are evident in the measured distributions. An observed double-peaked distribution in L is attributed, based on the model comparison, to a gap in the occurrence of solar proton events during the 2007 to 2011 solar minimum. Equatorial pitch angle distributions show that trapped solar protons are confined near the magnetic equator but that CRAND protons can reach low altitudes. Narrow pitch angle distributions near the outer edge of the Inner Belt are characteristic of proton trapping limits.
J. A. Sauvaud - One of the best experts on this subject based on the ideXlab platform.
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long term variations of quasi trapped and trapped electrons in the Inner Radiation Belt observed by demeter and sampex
Journal of Geophysical Research, 2020Co-Authors: Kun Zhang, Michael A. Temerin, M D Looper, H Zhao, Zheng Xiang, Leng Ying Khoo, J. A. SauvaudAbstract:Electrons in the Earth's Radiation Belts can be categorized into three populations: precipitating, quasi-trapped and trapped. We use data from the DEMETER and SAMPEX missions and from ground-based neutron monitors (NM) and sunspot observations to investigate the long-term variation of quasi-trapped and trapped sub-MeV electrons on different L shells in the Inner Belt. DEMETER and SAMPEX measurements span over 17 years and show that at $L \leq 1.14$ the electron flux is anti-correlated with sunspot number, but proportional to the cosmic ray intensity represented by NM count rates, which confirms that electrons at the Inner edge of the Inner Belt are produced by Cosmic Ray Albedo Neutron Decay (CRAND). The solar cycle variation of cosmic rays increased the electron flux at $L \leq 1.14$ by a factor of two from solar maximum at 2001 to solar minimum at 2009. At $L \ge 1.2$, both quasi-trapped and trapped electrons are enhanced during geomagnetic storms and decay to a background level during extended quiet times. At $L>2$, quasi-trapped electrons resemble trapped electrons, with correlation coefficients as high as 0.97, indicating that pitch angle scattering is the dominant process in this region.
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determining the spectra of Radiation Belt electron losses fitting demeter electron flux observations for typical and storm times
Journal of Geophysical Research, 2013Co-Authors: I Whittaker, Craig J. Rodger, Mark A. Clilverd, Rory J Gamble, J. A. SauvaudAbstract:[1] The energy spectra of energetic electron precipitation from the Radiation Belts are studied in order to improve our understanding of the influence of Radiation Belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electron spectra from DEMETER have been analyzed from all six years of its operation, and three fit types (power law, exponential, and kappa-type) have been applied to the precipitating flux observations. We show that the power law fit consistently provides the best representation of the flux and that the kappa-type is rarely valid. We also provide estimated uncertainties in the flux for this instrument as a function of energy. Average power law gradients for nontrapped particles have been determined for geomagnetically nondisturbed periods to get a typical global behavior of the spectra in the Inner Radiation Belt, slot region, and outer Radiation Belt. Power law spectral gradients in the outer Belt are typically −2.5 during quiet periods, changing to a softer spectrum of ∼−3.5 during geomagnetic storms. The Inner Belt does the opposite, hardening from −4 during quiet times to ∼−3 during storms. Typical outer Belt e-folding values are ∼200 keV, dropping to ∼150 keV during geomagnetic storms, while the Inner Belt e-folding values change from ∼120 keV to >200 keV. Analysis of geomagnetic storm periods show that the precipitating flux enhancements evident from such storms take approximately 13 days to return to normal values for the outer Belt and slot region and approximately 10 days for the Inner Belt.
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Inner Radiation Belt particle acceleration and energy structuring by drift resonance with ulf waves during geomagnetic storms
Journal of Geophysical Research, 2013Co-Authors: J. A. Sauvaud, M Walt, D C Delcourt, C Benoist, E Penou, Y Chen, C T RussellAbstract:[1] Geomagnetic storms are frequently associated with the formation of multiple bands of energetic electrons inside the Inner Radiation Belt at L = 1.1–1.9 and with prominent energy structures of protons inside the slot region at L = 2.2–3.5. These structures typically from 100 keV up to the MeV range result from coherent interactions of energetic particles with quasi-monochromatic ultra-low frequency (ULF) waves. These waves are induced by magnetospheric changes due to the arrival of dense solar material and related nightside injections of particles from the outer magnetosphere that destabilize field lines in the Inner magnetosphere down to L = 1.1. Using low-altitude data from the polar orbiting Demeter spacecraft, we perform case and statistical studies of these structures. We show that with such a spacecraft, these structures are best seen near the South Atlantic Anomaly because of lowering of the Belt particle mirror point. As evidenced from ground measurements, energy bands are associated with quasi-sinusoidal ULF Pc5 and Pc4 waves with periods in the 1000 s range for L = 1.1–1.9 and in the 60 s range for L = 2.2–3.5. Numerical simulations of the coherent drift resonance of energetic particles with ultra-low frequency waves show how the particles are accelerated and how the observed structures build up.
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DEMETER observations of transmitter-induced precipitation of Inner Radiation Belt electrons
Journal of Geophysical Research Space Physics, 2009Co-Authors: K. L. Graf, Umran S. Inan, D. Piddyachiy, P. Kulkarni, Michel Parrot, J. A. SauvaudAbstract:Near loss cone energetic electron flux increases induced by ground-based very low frequency (VLF) transmissions are observed directly via satellite-based detection. In 2 years of experiments ranging from 27 March 2006 through 2 April 2008 with the 21.4-kHz transmitter NPM in Lualualei, Hawaii, and the French satellite DEMETER (detection of electromagnetic emissions transmitted from earthquake regions), only a few cases of detection of individual pulses of transmitter-induced precipitation of Inner Radiation Belt electrons have been realized. Analysis of the specific cases of detection allow comparison of precipitating flux with predictions based on ray-tracing analyses of wave propagation and test particle modeling of the wave-particle interaction. Results indicate that the precipitated flux of >100 keV electrons induced by the NPM transmitter peaks at L ' 1.9 and, in the rare cases of detection, may be at higher energies than the $100 keV peak predicted by the model. The low detection rate is attributed to the orientation of the DEMETER particle detector, which is mostly overwhelmed by the trapped population at the location of detection.
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high energy electron detection onboard demeter the idp spectrometer description and first results on the Inner Belt
Planetary and Space Science, 2006Co-Authors: J. A. Sauvaud, E Penou, T Moreau, R Maggiolo, J P Treilhou, C Jacquey, A Cros, J Coutelier, J Rouzaud, M GangloffAbstract:Abstract This paper gives a description and the first results of the electron spectrometer placed onboard the Demeter satellite. This detector with a large geometrical factor is aimed to measure trapped electron fluxes in the energy range from 70 keV to about 0.8 MeV and to provide information on the electron fluxes between 0.8 and 2.5 MeV. The energy resolution, better than 10 keV, and the 256 energy channels allow to obtain insights on the Radiation Belt structure. The data received during 2004 show for the first time that the low-energy component of the Inner Radiation Belt ( 1.1 L 1.35 ) consists of the superposition of quasi-mono-energetic peaks as expected from the interaction of electrons with a large number of high-powered Earth-based VLF emitters in the frequency range 10–100 kHz distributed along the particle longitudinal drift around the Earth. This energy-layered structure appears to depend on the longitude, being particularly evident in low magnetic field regions where particles from the Inner Belt can easily reach the satellite altitude. This happens locally West of America and inside the South Atlantic Anomaly itself. We show that the variation of the energy of the peaks as a function of the McIlwain parameter can be used to compute the altitude profile of the equatorial thermal electron content corresponding to the transition between the upper ionosphere and the plasmasphere.
B T Kress - One of the best experts on this subject based on the ideXlab platform.
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simulations of Inner Radiation Belt proton loss during geomagnetic storms
Journal of Geophysical Research, 2015Co-Authors: M Engel, B T Kress, M K Hudson, R S SelesnickAbstract:The loss of protons in the outer part of the Inner Radiation Belt (L = 2 to 3) during the 6 April 2000 solar energetic particles event has been investigated using test particle simulations that follow full Lorentz trajectories with both magnetic and electric fields calculated from an empirical model. The electric fields are calculated as inductive fields generated by the time-changing magnetic field, which is achieved by time stepping analytic magnetic fields. The simulation results are compared with proton measurements from the highly elliptical orbit satellite for three different energy ranges (8.5–35 MeV, 16–40 MeV, and 27–45 MeV) as well as previous modeling work done. In previous work, Inner zone Radiation Belt loss during geomagnetic storms has been modeled by simulating field line curvature scattering in static magnetic field snapshots with no electric field. The inclusion of the inductive electric field causes an increase in loss to lower L shells, improving the agreement with the satellite data.
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observations of the Inner Radiation Belt crand and trapped solar protons
Journal of Geophysical Research, 2014Co-Authors: R S Selesnick, Shrikanth G. Kanekal, D N Baker, M K Hudson, A N Jaynes, B T KressAbstract:Measurements of Inner Radiation Belt protons have been made by the Van Allen Probes Relativistic Electron-Proton Telescopes as a function of kinetic energy (24 to 76 MeV), equatorial pitch angle, and magnetic L shell, during late 2013 and early 2014. A probabilistic data analysis method reduces background from contamination by higher-energy protons. Resulting proton intensities are compared to predictions of a theoretical Radiation Belt model. Then trapped protons originating both from cosmic ray albedo neutron decay (CRAND) and from trapping of solar protons are evident in the measured distributions. An observed double-peaked distribution in L is attributed, based on the model comparison, to a gap in the occurrence of solar proton events during the 2007 to 2011 solar minimum. Equatorial pitch angle distributions show that trapped solar protons are confined near the magnetic equator but that CRAND protons can reach low altitudes. Narrow pitch angle distributions near the outer edge of the Inner Belt are characteristic of proton trapping limits.
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injection and loss of Inner Radiation Belt protons during solar proton events and magnetic storms
Journal of Geophysical Research, 2010Co-Authors: R S Selesnick, M K Hudson, B T KressAbstract:[1] A survey of 27 to 45 MeV proton measurements from the HEO-3 satellite during the years 1998 through 2005 has been taken to describe variability in the outer part of the Inner Radiation Belt and slot region (L = 2 to 3). Rapid (∼1-day) changes are described as injection or loss events, characterized respectively by Gaussian or exponential L dependencies. The radial extent of both event types is correlated to the minimum Dst of associated magnetic storms, while the injection magnitude is correlated to the flux of associated interplanetary solar proton events. Changes in the maximal L of observed trapped protons are consistent with trapping limits estimated from magnetic field line curvature. The inward extent and energy independence of the observed loss events are inconsistent with field line curvature induced scattering in a static magnetic field. However, time-dependent geomagnetic cutoff suppression, observed during magnetic storms, may be the cause of significant losses. Drift resonance with electric field impulses caused by rapid magnetospheric compression is the likely cause of both solar proton injections and radial shifts of preexisting trapped protons.
Qiugang Zong - One of the best experts on this subject based on the ideXlab platform.
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test particle simulation on the ion and electron zebra stripes and their time evolution in Inner Radiation Belt
Science China-technological Sciences, 2018Co-Authors: Qiugang Zong, Yongfu Wang, X Z ZhouAbstract:During February 15–16, 2014, the energetic electron spectrogram for four successive Inner Radiation Belt crossing show clearly the electron zebra structures and their time evolution which last for about 17 h. Unfortunately, the time of flight (TOF) in RBSPICE measurement is turned off below 3 R E, and the ion measurement is contaminated by electrons. Thus in this study we studied the differences between the ion and electron zebra stripe structures and their time evolution using simple theory and test particle simulation, combining the electron measurement from RBSIPICE onboard Van Allen Probes. Theoretical analysis predicts that the ion zebra stripe structures should lie at a higher energy range than the corresponding electron zebra stripe structures due to that the directions of gradient B drift and corotation E × B drift are the same for electrons while opposite for ions. Test particle simulation with the dipole magnetic field and Volland-Stern electric field model have shown that the ion and electron zebra stripe structures could be produced by the convection electric field penetrating into the Inner magnetosphere in this event, with their time evolution determined by total drift velocity that are different for ions and electrons. The predicted differences between the ion and electron zebra stripe structures are partially verified through observation. The ion zebra stripe structures could have potential influence to the ring current.
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short term variations of the Inner Radiation Belt in the south atlantic anomaly
Journal of Geophysical Research, 2015Co-Authors: Hong Zou, G K Parks, Qiugang Zong, Hong Fei Chen, Lun Xie, Xianguo ZhangAbstract:Long-term variations of South Atlantic anomaly (SAA) are generally derived by fitting a Gaussian-like function to an averaged distribution of the proton flux at a certain altitude accumulated over time periods for a month or longer. These data do not show the short-term variation of SAA arising from geomagnetic storm effects whose time scale is less than a month. To investigate the short-term variations, the features of SAA for the high-energy protons detected by NOAA Polar Orbiting Environmental Satellites during 1998-2008 have been investigated with a 5 day running average method. It is found that the two SAA parameters for three proton channels reflect the maximal proton flux in SAA and the extension of SAA decreases several percent during geomagnetic storms. Possible reasons for the decreases of the two SAA parameters for high-energy protons are discussed. Proton losses at the outer boundary of the Inner Radiation Belt can be explained by the field line curvature scattering mechanism, while the decrease of the proton flux near the center of SAA is probably caused by the enhanced neutral atmospheric density during geomagnetic storms. The study of the behavior of high-energy protons in SAA is useful for understanding of storm time and long-term variations of the Radiation environment near Earth and for constructing dynamic Radiation Belt models.
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response of high energy protons of the Inner Radiation Belt to large magnetic storms
Journal of Geophysical Research, 2011Co-Authors: G K Parks, Hong Zou, Qiugang Zong, Hong Fei Chen, Lun XieAbstract:[1] The responses of the high-energy protons (35–70 MeV, 70–140 MeV and 140–500 MeV) below L = 3 to the large geomagnetic magnetic storms (|Dst| > 200 nT) during 1998 to 2005 have been investigated with the measurements by three NOAA POES satellites (NOAA-15, 16 and 17). The losses of protons in the outer region of the Inner Radiation Belt are found during the large storms. Similar loss events were also measured by the HEO-3 satellite for lower energy protons (8.5–35 MeV, 16–40 MeV and 27–45 MeV). However, the response of higher energy protons to the storms observed by NOAA satellites is different from that of the lower energy protons. It is shown that some aspects of the loss event and energy dependence during large storms can be accounted for by the trapping limit of the field line curvature scattering mechanism. The maximal L shells of the observed trapped protons are consistent with the critical L shells of the field line curvature scattering. The modeling results based on the storm-time geomagnetic field model (TS04c) and the Radiation Belt model (AP8) show the inward motion of the outer boundary of trapped protons is caused by the distortion of geomagnetic field during the magnetic storms and depends on proton energy. The additional proton loss in the lower energy channel (35–70 MeV) could be attributed to the storm-caused weakening of geomagnetic field combined with L dependent lifetimes induced by curvature scattering during magnetic storms.
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pitch angle distribution evolution of energetic electrons in the Inner Radiation Belt and slot region during the 2003 halloween storm
Journal of Geophysical Research, 2009Co-Authors: Qiugang Zong, Fuliang Xiao, Liangxu ChenAbstract:This injection of energetic electrons into the slot region may be associated with the plasmapause movement and Hiss/Chorus enhancement. This flux enhancement is possibly associated with convective transport from the plasma sheet, enhanced radial diffusion and local wave-particle interaction acceleration. By adopting a fitting parameter of loss time tL we solved the bounce-averaged pitch angle diffusion equation driven by field-aligned whistler-mode waves (including chorus and hiss). We show that pitch-angle scattering can account for the pitch-angle distribution evolution in 30–500 keVelectrons in the Innermost Radiation Belt near L = 1.7 (as observed by Polar satellite) and the slot region 2 < L <3 . Inparticular,simulatedresultsindicatethattheloss-coneregionisalmostempty,andoutside the loss-cone region both flux and anisotropy of energetic electrons are reduced with the gyroresonant time. The obtained time scale for the pitch-angle distribution evolution is found to be approximately tens of hours, consistent with observation.
Hong Zou - One of the best experts on this subject based on the ideXlab platform.
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short term variations of the Inner Radiation Belt in the south atlantic anomaly
Journal of Geophysical Research, 2015Co-Authors: Hong Zou, G K Parks, Qiugang Zong, Hong Fei Chen, Lun Xie, Xianguo ZhangAbstract:Long-term variations of South Atlantic anomaly (SAA) are generally derived by fitting a Gaussian-like function to an averaged distribution of the proton flux at a certain altitude accumulated over time periods for a month or longer. These data do not show the short-term variation of SAA arising from geomagnetic storm effects whose time scale is less than a month. To investigate the short-term variations, the features of SAA for the high-energy protons detected by NOAA Polar Orbiting Environmental Satellites during 1998-2008 have been investigated with a 5 day running average method. It is found that the two SAA parameters for three proton channels reflect the maximal proton flux in SAA and the extension of SAA decreases several percent during geomagnetic storms. Possible reasons for the decreases of the two SAA parameters for high-energy protons are discussed. Proton losses at the outer boundary of the Inner Radiation Belt can be explained by the field line curvature scattering mechanism, while the decrease of the proton flux near the center of SAA is probably caused by the enhanced neutral atmospheric density during geomagnetic storms. The study of the behavior of high-energy protons in SAA is useful for understanding of storm time and long-term variations of the Radiation environment near Earth and for constructing dynamic Radiation Belt models.
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solar cycle variations of trapped proton flux in the Inner Radiation Belt
Journal of Geophysical Research, 2014Co-Authors: Hong Zou, Murong Qin, Xianguo Zhang, Hongqiang Song, Yueqiang SunAbstract:Trapped proton population in the Inner Radiation Belt is highly dense, posing a potential danger to astronauts and man-made space assets traversing through this region. While being significantly stable within timescales up to hundreds of days, Inner zone proton fluxes can exhibit considerable solar cycle variations, which has not been investigated comprehensively yet. To analyze the long-term variation of the South Atlantic Anomaly (SAA), we adopt the proton flux data measured by NOAA 15 from 1999 through 2009 and perform statistical analyses on the basis of reasonable Gaussian fits. We report that the variation of the peak proton flux in the SAA is anticorrelated with that of F-10.7 during a solar cycle. There also exists a phase lag of 685 days between the solar F-10.7 flux and the proton flux. Similar features are seen for changes of the SAA distribution area, which in addition shows a rapid decrease during the solar maximum and a slow increase during the solar minimum. We also find that the region where the proton flux peaks drifts westward year by year with larger drift rates during the solar minimum. The peak region shifts southward during the solar maximum but in the opposite direction during the solar minimum with higher shift speed. Enhancements in solar wind dynamic pressure can favor the north-south drift of the SAA.
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response of high energy protons of the Inner Radiation Belt to large magnetic storms
Journal of Geophysical Research, 2011Co-Authors: G K Parks, Hong Zou, Qiugang Zong, Hong Fei Chen, Lun XieAbstract:[1] The responses of the high-energy protons (35–70 MeV, 70–140 MeV and 140–500 MeV) below L = 3 to the large geomagnetic magnetic storms (|Dst| > 200 nT) during 1998 to 2005 have been investigated with the measurements by three NOAA POES satellites (NOAA-15, 16 and 17). The losses of protons in the outer region of the Inner Radiation Belt are found during the large storms. Similar loss events were also measured by the HEO-3 satellite for lower energy protons (8.5–35 MeV, 16–40 MeV and 27–45 MeV). However, the response of higher energy protons to the storms observed by NOAA satellites is different from that of the lower energy protons. It is shown that some aspects of the loss event and energy dependence during large storms can be accounted for by the trapping limit of the field line curvature scattering mechanism. The maximal L shells of the observed trapped protons are consistent with the critical L shells of the field line curvature scattering. The modeling results based on the storm-time geomagnetic field model (TS04c) and the Radiation Belt model (AP8) show the inward motion of the outer boundary of trapped protons is caused by the distortion of geomagnetic field during the magnetic storms and depends on proton energy. The additional proton loss in the lower energy channel (35–70 MeV) could be attributed to the storm-caused weakening of geomagnetic field combined with L dependent lifetimes induced by curvature scattering during magnetic storms.