The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Yuri Shprits - One of the best experts on this subject based on the ideXlab platform.
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formation of electron Radiation Belts at saturn by z mode wave acceleration
Nature Communications, 2018Co-Authors: E E Woodfield, Richard B. Horne, Yuri Shprits, Sarah A Glauert, J D Menietti, W S KurthAbstract:At Saturn electrons are trapped in the planet’s magnetic field and accelerated to relativistic energies to form the Radiation Belts, but how this dramatic increase in electron energy occurs is still unknown. Until now the mechanism of radial diffusion has been assumed but we show here that in-situ acceleration through wave particle interactions, which initial studies dismissed as ineffectual at Saturn, is in fact a vital part of the energetic particle dynamics there. We present evidence from numerical simulations based on Cassini spacecraft data that a particular plasma wave, known as Z-mode, accelerates electrons to MeV energies inside 4 RS (1 RS = 60,330 km) through a Doppler shifted cyclotron resonant interaction. Our results show that the Z-mode waves observed are not oblique as previously assumed and are much better accelerators than O-mode waves, resulting in an electron energy spectrum that closely approaches observed values without any transport effects included. Radial diffusion is the only mechanism considered to accelerate trapped electrons to relativistic energies in Saturn’s magnetic field, forming Radiation Belts. Here the authors show another mechanism, electron acceleration via Doppler shifted cyclotron resonant interaction with Z-mode waves, which can form Radiation Belts inside the orbit of Enceladus.
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wave induced loss of ultra relativistic electrons in the van allen Radiation Belts
Nature Communications, 2016Co-Authors: O V Agapitov, Yuri Shprits, A Drozdov, M Spasojevic, A C Kellerman, M Usanova, M J Engebretson, Irina ZhelavskayaAbstract:The dipole configuration of the Earth's magnetic field allows for the trapping of highly energetic particles, which form the Radiation Belts. Although significant advances have been made in understanding the acceleration mechanisms in the Radiation Belts, the loss processes remain poorly understood. Unique observations on 17 January 2013 provide detailed information throughout the Belts on the energy spectrum and pitch angle (angle between the velocity of a particle and the magnetic field) distribution of electrons up to ultra-relativistic energies. Here we show that although relativistic electrons are enhanced, ultra-relativistic electrons become depleted and distributions of particles show very clear telltale signatures of electromagnetic ion cyclotron wave-induced loss. Comparisons between observations and modelling of the evolution of the electron flux and pitch angle show that electromagnetic ion cyclotron waves provide the dominant loss mechanism at ultra-relativistic energies and produce a profound dropout of the ultra-relativistic Radiation belt fluxes.
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unusual stable trapping of the ultrarelativistic electrons in the van allen Radiation Belts
Nature Physics, 2013Co-Authors: Yuri Shprits, A Drozdov, A C Kellerman, M Usanova, D Subbotin, K OrlovaAbstract:The Van Allen Radiation Belts are two rings of charged particles encircling the Earth. Therefore the transient appearance in 2012 of a third ring between the inner and outer Belts was a surprise. A study of the ultrarelativistic electrons in this middle ring reveals new physics for particles above 2 MeV.
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locations of boundaries of outer and inner Radiation Belts as observed by cluster and double star
Journal of Geophysical Research, 2011Co-Authors: Yu N Ganushkina, I Dandouras, Yuri Shprits, J B CaoAbstract:Cluster CIS ion spectrograms measured during the period of the recent solar minimum between April 2007 and June 2009, when Cluster was deep in the Radiation Belts with its perigee as close as L = 2, are analyzed. The analysis is complemented by Double Star TC-1 satellite data from HIA ion spectrograms on perigee passes during the period of May 15, 2007 to September 28, 2007. We demonstrate how the background counts produced by energetic particles of the Radiation Belts in Cluster CIS and Double Star HIA instruments can be interpreted to obtain the locations of the boundaries of the outer and inner Belts. The obtained L-MLT distribution of boundaries reflects the general structure of the Radiation Belts. Closer examination of the time-dependent L locations of the boundaries reveals several dips to lower L-shells (from L = 6 to L = 4) in the outer boundary location. The importance of the solar wind pressure increases for the Earthward shift of the outer boundary of the outer belt is discussed. The location and thickness of the slot region are studied using the determined inner boundaries of the outer belt and the outer boundaries of the inner belt. It was found that during intervals of low activity in the solar wind parameters, the slot region widens, which is consistent with weaker inward radial diffusion, and also with weaker local acceleration that can occur only at higher L-shells outside the plasmasphere. We conclude that boundaries of Radiation Belts determined from background measurements on the instruments with energy ranges that do not cover the Radiation Belts' energies provide valuable additional information that is useful for Radiation Belts' model development and validation.
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Wave acceleration of electrons in the Van Allen Radiation Belts
Nature, 2005Co-Authors: Richard B. Horne, Daniel N. Baker, Shrikanth G. Kanekal, Yuri Shprits, Sarah A Glauert, M J Engebretson, Nigel P Meredith, Richard M. Thorne, Andrew Smith, J. L. PoschAbstract:The Van Allen Radiation Belts are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth's magnetic field. Their properties vary according to solar activity and they represent a hazard to satellites and humans in space. An important challenge has been to explain how the charged particles within these Belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer Radiation belt was depleted and then re-formed closer to the Earth, that the long established theory of acceleration by radial diffusion is inadequate; the electrons are accelerated more effectively by electromagnetic waves at frequencies of a few kilohertz. Wave acceleration can increase the electron flux by more than three orders of magnitude over the observed timescale of one to two days, more than sufficient to explain the new Radiation belt. Wave acceleration could also be important for Jupiter, Saturn and other astrophysical objects with magnetic fields.
D N Baker - One of the best experts on this subject based on the ideXlab platform.
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space weather effects in the earth s Radiation Belts
Space Science Reviews, 2018Co-Authors: D N Baker, A N Jaynes, P. J. Erickson, Joseph F. Fennell, J. C. Foster, P T VerronenAbstract:The first major scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or Belts, of very high-energy magnetically trapped charged particles. Early observations of the Radiation environment clearly indicated that the Van Allen Belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. The energy distribution, spatial extent and particle species makeup of the Van Allen Belts has been subsequently explored by several space missions. Recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed many novel properties of the Radiation Belts, especially for electrons at highly relativistic and ultra-relativistic kinetic energies. In this review we summarize the space weather impacts of the Radiation Belts. We demonstrate that many remarkable features of energetic particle changes are driven by strong solar and solar wind forcings. Recent comprehensive data show broadly and in many ways how high energy particles are accelerated, transported, and lost in the magnetosphere due to interplanetary shock wave interactions, coronal mass ejection impacts, and high-speed solar wind streams. We also discuss how Radiation belt particles are intimately tied to other parts of the geospace system through atmosphere, ionosphere, and plasmasphere coupling. The new data have in many ways rewritten the textbooks about the Radiation Belts as a key space weather threat to human technological systems.
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Space Weather Effects in the Earth’s Radiation Belts
Space Science Reviews, 2017Co-Authors: D N Baker, A N Jaynes, P. J. Erickson, Joseph F. Fennell, J. C. Foster, P T VerronenAbstract:The first major scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or Belts, of very high-energy magnetically trapped charged particles. Early observations of the Radiation environment clearly indicated that the Van Allen Belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. The energy distribution, spatial extent and particle species makeup of the Van Allen Belts has been subsequently explored by several space missions. Recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed many novel properties of the Radiation Belts, especially for electrons at highly relativistic and ultra-relativistic kinetic energies. In this review we summarize the space weather impacts of the Radiation Belts. We demonstrate that many remarkable features of energetic particle changes are driven by strong solar and solar wind forcings. Recent comprehensive data show broadly and in many ways how high energy particles are accelerated, transported, and lost in the magnetosphere due to interplanetary shock wave interactions, coronal mass ejection impacts, and high-speed solar wind streams. We also discuss how Radiation belt particles are intimately tied to other parts of the geospace system through atmosphere, ionosphere, and plasmasphere coupling. The new data have in many ways rewritten the textbooks about the Radiation Belts as a key space weather threat to human technological systems.
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an impenetrable barrier to ultrarelativistic electrons in the van allen Radiation Belts
Nature, 2014Co-Authors: D N Baker, A N Jaynes, P. J. Erickson, J. C. Foster, Shrikanth G. Kanekal, R. M. Thorne, V C Hoxie, J F Fennell, J R Wygant, W S KurthAbstract:Analysis of data obtained by probe spacecraft shows that ultrarelativistic electrons in the Van Allen Radiation Belts are prevented from entering a sharply defined region around the Earth, possibly owing to a combination of slow natural inward diffusion and pitch angle scattering. Recent observations made by NASA's Van Allen Probes mission revealed previously unknown properties of the Radiation Belts surrounding the Earth, especially at ultrarelativistic kinetic energies of greater than five megaelectronvolts. Using high spatial and temporal resolution data from the same probes, Daniel Baker et al. identify an extremely sharp inner boundary for the ultrarelativistic electrons. The authors suggest that this almost impenetrable barrier to inward electron radial transport arises as a result of exceptionally slow natural inward radial diffusion combined with wave-particle pitch angle scattering deep inside the Earth's plasmasphere. Early observations1,2 indicated that the Earth’s Van Allen Radiation Belts could be separated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies3,4 showed that electrons of moderate energy (less than about one megaelectronvolt) often populate both zones, with a deep ‘slot’ region largely devoid of particles between them. There is a region of dense cold plasma around the Earth known as the plasmasphere, the outer boundary of which is called the plasmapause. The two-belt Radiation structure was explained as arising from strong electron interactions with plasmaspheric hiss just inside the plasmapause boundary5, with the inner edge of the outer Radiation zone corresponding to the minimum plasmapause location6. Recent observations have revealed unexpected Radiation belt morphology7,8, especially at ultrarelativistic kinetic energies9,10 (more than five megaelectronvolts). Here we analyse an extended data set that reveals an exceedingly sharp inner boundary for the ultrarelativistic electrons. Additional, concurrently measured data11 reveal that this barrier to inward electron radial transport does not arise because of a physical boundary within the Earth’s intrinsic magnetic field, and that inward radial diffusion is unlikely to be inhibited by scattering by electromagnetic transmitter wave fields. Rather, we suggest that exceptionally slow natural inward radial diffusion combined with weak, but persistent, wave–particle pitch angle scattering deep inside the Earth’s plasmasphere can combine to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.
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Acceleration of Particles to High Energies in Earth’s Radiation Belts
Space Science Reviews, 2012Co-Authors: R. M. Millan, D N BakerAbstract:Discovered in 1958, Earth’s Radiation Belts persist in being mysterious and unpredictable. This highly dynamic region of near-Earth space provides an important natural laboratory for studying the physics of particle acceleration. Despite the proximity of the Radiation Belts to Earth, many questions remain about the mechanisms responsible for rapidly energizing particles to relativistic energies there. The importance of understanding the Radiation Belts continues to grow as society becomes increasingly dependent on spacecraft for navigation, weather forecasting, and more. We review the historical underpinning and observational basis for our current understanding of particle acceleration in the Radiation Belts.
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long term measurements of Radiation Belts by sampex and their variations
Geophysical Research Letters, 2001Co-Authors: D N Baker, M. D. Looper, S G Kanekal, M TemerinAbstract:The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), a low-altitude and polar-orbiting satellite, has provided a long-term global picture of the Radiation Belts since its launch on July 3, 1992. While the inner belt (L 2) electrons vary on solar cycle, semiannual, and solar rotation time scales, and with geomagnetic storms. Recently developed models of predicting MeV electron at geostationary orbit [Li et al., 2001] and the Dst index [Temerin and Li, 2001] based on solar wind measurements are used to examine the cause of the prominent semiannual variations of outer belt electrons and the Dst index. The equinoctial effect (the angle between the Earth's dipole and the flow direction of the solar wind) contributes most to the semiannual variation of the Dst and MeV electrons deep in the inner magnetosphere (L < 5). The semiannual variation of MeV electrons at geostationary orbit is attributed mostly to the semiannual variation of solar wind velocity.
K Orlova - One of the best experts on this subject based on the ideXlab platform.
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unusual stable trapping of the ultrarelativistic electrons in the van allen Radiation Belts
Nature Physics, 2013Co-Authors: Yuri Shprits, A Drozdov, A C Kellerman, M Usanova, D Subbotin, K OrlovaAbstract:The Van Allen Radiation Belts are two rings of charged particles encircling the Earth. Therefore the transient appearance in 2012 of a third ring between the inner and outer Belts was a surprise. A study of the ultrarelativistic electrons in this middle ring reveals new physics for particles above 2 MeV.
R. M. Thorne - One of the best experts on this subject based on the ideXlab platform.
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observations of mev electrons in jupiter s innermost Radiation Belts and polar regions by the juno Radiation monitoring investigation perijoves 1 and 3
Geophysical Research Letters, 2017Co-Authors: Heidi N Becker, S. J. Bolton, D Santoscosta, John Leif Jorgensen, Troelz Denver, A Adriani, A Mura, J E P Connerney, S Levin, R. M. ThorneAbstract:Juno's “Perijove 1” (27 August 2016) and “Perijove 3” (11 December 2016) flybys through the innermost region of Jupiter's magnetosphere (radial distances 5 MeV and >10 MeV electron fluxes derived from these measurements provide valuable constraints for models of relativistic electron environments in the inner Radiation Belts. Several intense bursts of high-energy particle counts were also observed by the Advanced Stellar Compass in polar regions outside the Radiation Belts.
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an impenetrable barrier to ultrarelativistic electrons in the van allen Radiation Belts
Nature, 2014Co-Authors: D N Baker, A N Jaynes, P. J. Erickson, J. C. Foster, Shrikanth G. Kanekal, R. M. Thorne, V C Hoxie, J F Fennell, J R Wygant, W S KurthAbstract:Analysis of data obtained by probe spacecraft shows that ultrarelativistic electrons in the Van Allen Radiation Belts are prevented from entering a sharply defined region around the Earth, possibly owing to a combination of slow natural inward diffusion and pitch angle scattering. Recent observations made by NASA's Van Allen Probes mission revealed previously unknown properties of the Radiation Belts surrounding the Earth, especially at ultrarelativistic kinetic energies of greater than five megaelectronvolts. Using high spatial and temporal resolution data from the same probes, Daniel Baker et al. identify an extremely sharp inner boundary for the ultrarelativistic electrons. The authors suggest that this almost impenetrable barrier to inward electron radial transport arises as a result of exceptionally slow natural inward radial diffusion combined with wave-particle pitch angle scattering deep inside the Earth's plasmasphere. Early observations1,2 indicated that the Earth’s Van Allen Radiation Belts could be separated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies3,4 showed that electrons of moderate energy (less than about one megaelectronvolt) often populate both zones, with a deep ‘slot’ region largely devoid of particles between them. There is a region of dense cold plasma around the Earth known as the plasmasphere, the outer boundary of which is called the plasmapause. The two-belt Radiation structure was explained as arising from strong electron interactions with plasmaspheric hiss just inside the plasmapause boundary5, with the inner edge of the outer Radiation zone corresponding to the minimum plasmapause location6. Recent observations have revealed unexpected Radiation belt morphology7,8, especially at ultrarelativistic kinetic energies9,10 (more than five megaelectronvolts). Here we analyse an extended data set that reveals an exceedingly sharp inner boundary for the ultrarelativistic electrons. Additional, concurrently measured data11 reveal that this barrier to inward electron radial transport does not arise because of a physical boundary within the Earth’s intrinsic magnetic field, and that inward radial diffusion is unlikely to be inhibited by scattering by electromagnetic transmitter wave fields. Rather, we suggest that exceptionally slow natural inward radial diffusion combined with weak, but persistent, wave–particle pitch angle scattering deep inside the Earth’s plasmasphere can combine to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.
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electron acceleration in the van allen Radiation Belts by fast magnetosonic waves
Geophysical Research Letters, 2007Co-Authors: Richard B. Horne, R. M. Thorne, Sarah A Glauert, Nigel P Meredith, D Pokhotelov, O SantolikAbstract:[1] Local acceleration is required to explain electron flux increases in the outer Van Allen Radiation belt during magnetic storms. Here we show that fast magnetosonic waves, detected by Cluster 3, can accelerate electrons between ∼10 keV and a few MeV inside the outer Radiation belt. Acceleration occurs via electron Landau resonance, and not Doppler shifted cyclotron resonance, due to wave propagation almost perpendicular to the ambient magnetic field. Using quasi-linear theory, pitch angle and energy diffusion rates are comparable to those for whistler mode chorus, suggesting that these waves are very important for local electron acceleration. Since pitch angle diffusion does not extend into the loss cone, these waves, on their own, are not important for loss to the atmosphere. We suggest that magnetosonic waves, which are generated by unstable proton ring distributions, are an important energy transfer process from the ring current to the Van Allen Radiation Belts.
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Synchrontron measurments of Jupiter's inner Radiation Belts
2002Co-Authors: M. J. Klein, S. J. Bolton, S. Gulkis, M. A. Janssen, S. M. Levin, R. M. ThorneAbstract:In this paper we discuss recent observations on the study of synchrotron radio emission from Jupiter's inner Radiation Belts.
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ultra relativistic electrons in jupiter s Radiation Belts
Nature, 2002Co-Authors: S. J. Bolton, R. M. Thorne, S Levin, M Janssen, M Klein, Samuel Gulkis, T Bastian, R J Sault, C Elachi, Mark HofstadterAbstract:Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission1: thermal atmospheric emission and synchrotron emission2 from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements3,4 confirmed the existence of Jupiter's high-energy electron-Radiation Belts, with evidence for electrons at energies up to 20 MeV. Although most Radiation belt models predict electrons at higher energies5,6, adiabatic diffusion theory can account only for energies up to around 20 MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8 GHz synchrotron emission that confirm the presence of electrons with energies up to 50 MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20 MeV are more numerous than previously believed.
Richard B. Horne - One of the best experts on this subject based on the ideXlab platform.
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formation of electron Radiation Belts at saturn by z mode wave acceleration
Nature Communications, 2018Co-Authors: E E Woodfield, Richard B. Horne, Yuri Shprits, Sarah A Glauert, J D Menietti, W S KurthAbstract:At Saturn electrons are trapped in the planet’s magnetic field and accelerated to relativistic energies to form the Radiation Belts, but how this dramatic increase in electron energy occurs is still unknown. Until now the mechanism of radial diffusion has been assumed but we show here that in-situ acceleration through wave particle interactions, which initial studies dismissed as ineffectual at Saturn, is in fact a vital part of the energetic particle dynamics there. We present evidence from numerical simulations based on Cassini spacecraft data that a particular plasma wave, known as Z-mode, accelerates electrons to MeV energies inside 4 RS (1 RS = 60,330 km) through a Doppler shifted cyclotron resonant interaction. Our results show that the Z-mode waves observed are not oblique as previously assumed and are much better accelerators than O-mode waves, resulting in an electron energy spectrum that closely approaches observed values without any transport effects included. Radial diffusion is the only mechanism considered to accelerate trapped electrons to relativistic energies in Saturn’s magnetic field, forming Radiation Belts. Here the authors show another mechanism, electron acceleration via Doppler shifted cyclotron resonant interaction with Z-mode waves, which can form Radiation Belts inside the orbit of Enceladus.
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space weather impacts on satellites and forecasting the earth s electron Radiation Belts with spacecast
Space Weather-the International Journal of Research and Applications, 2013Co-Authors: Richard B. Horne, Daniel Boscher, Sarah A Glauert, Nigel P Meredith, Vincent Maget, D Heynderickx, David PitchfordAbstract:[1] Satellites can be damaged by high energy charged particles in the Earth's Radiation Belts and during solar energetic particle (SEP) events. Here we review the growing reliance on satellite services, new vulnerabilities to space weather, and previous events that have led to loss of service. We describe a new European system to forecast the Radiation Belts up to 3 h ahead, which has three unique features: first, it uses physics-based models, which include wave-particle interactions; second, it provides a forecast for the whole outer Radiation belt including geostationary, medium, and slot region orbits; third, it is a truly international effort including Europe, United States, and Japan. During the 8–9 March 2012 storm and SEP event, the models were able to forecast the >800 keV electron flux to within a factor of 2 initially, and later to within a factor of 10 of the GOES data. Although ACE and GOES data became unreliable during the SEP event, the system continued forecasting without interruption using ground-based magnetometers. A forecast of the 24 h electron fluence >2 MeV is used to provide a risk index for satellite operators. We show that including wave-particle interactions for L* > 6.5 improves the agreement with GOES data substantially and that a fast inward motion of the magnetopause to L* < 8 is related to rapid loss of relativistic electrons at geostationary orbit. Thus, we suggest that better wave-particle models and better coupling between the solar wind and the models of the magnetopause and Radiation Belts should lead to better forecasting.
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forecasting the earth s Radiation Belts and modelling solar energetic particle events recent results from spacecast
Journal of Space Weather and Space Climate, 2013Co-Authors: Richard B. Horne, Sarah A Glauert, Nigel P Meredith, H Koskinen, R Vainio, Alexandr Afanasiev, Natalia Ganushkina, O A AmariuteiAbstract:High-energy charged particles in the van Allen Radiation Belts and in solar energetic particle events can damage satellites on orbit leading to malfunctions and loss of satellite service. Here we describe some recent results from the SPACECAST project on modelling and forecasting the Radiation Belts, and modelling solar energetic particle events. We describe the SPACECAST forecasting system that uses physical models that include wave-particle interactions to forecast the electron Radiation Belts up to 3 h ahead. We show that the forecasts were able to reproduce the >2 MeV electron flux at GOES 13 during the moderate storm of 7–8 October 2012, and the period following a fast solar wind stream on 25–26 October 2012 to within a factor of 5 or so. At lower energies of 10 – a few 100 keV we show that the electron flux at geostationary orbit depends sensitively on the high-energy tail of the source distribution near 10 RE on the nightside of the Earth, and that the source is best represented by a kappa distribution. We present a new model of whistler mode chorus determined from multiple satellite measurements which shows that the effects of wave-particle interactions beyond geostationary orbit are likely to be very significant. We also present radial diffusion coefficients calculated from satellite data at geostationary orbit which vary with Kp by over four orders of magnitude. We describe a new automated method to determine the position at the shock that is magnetically connected to the Earth for modelling solar energetic particle events and which takes into account entropy, and predict the form of the mean free path in the foreshock, and particle injection efficiency at the shock from analytical theory which can be tested in simulations.
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Forecasting the Radiation Belts in Europe
Space Weather, 2012Co-Authors: Richard B. HorneAbstract:Weather forecasting has expanded to space weather. As of 1 March 2012, satellite operators and the general public will be able to obtain forecasts of the Earth’s Radiation Belts, thanks to the SPACECAST project. The opening of the first European system to forecast Earth’s Radiation Belts, part of the SPACECAST project, is funded by the European Union Framework 7 Programme and provides a forecast of high-energy electrons up to 3 hours in advance (updated every hour), as well as a risk index for the satellite operations and service industry.
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electron acceleration in the van allen Radiation Belts by fast magnetosonic waves
Geophysical Research Letters, 2007Co-Authors: Richard B. Horne, R. M. Thorne, Sarah A Glauert, Nigel P Meredith, D Pokhotelov, O SantolikAbstract:[1] Local acceleration is required to explain electron flux increases in the outer Van Allen Radiation belt during magnetic storms. Here we show that fast magnetosonic waves, detected by Cluster 3, can accelerate electrons between ∼10 keV and a few MeV inside the outer Radiation belt. Acceleration occurs via electron Landau resonance, and not Doppler shifted cyclotron resonance, due to wave propagation almost perpendicular to the ambient magnetic field. Using quasi-linear theory, pitch angle and energy diffusion rates are comparable to those for whistler mode chorus, suggesting that these waves are very important for local electron acceleration. Since pitch angle diffusion does not extend into the loss cone, these waves, on their own, are not important for loss to the atmosphere. We suggest that magnetosonic waves, which are generated by unstable proton ring distributions, are an important energy transfer process from the ring current to the Van Allen Radiation Belts.
