Found 4 entries in the Bibliography.
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Abstract The plasma mass loading of the terrestrial equatorial inner magnetosphere is a key determinant of the characteristics and propagation of ULF waves. Electron number density is also an important factor for other types of waves such as chorus, hiss and EMIC waves. In this paper, we use Van Allen Probe data from September 2012 to February 2019 to create average models of electron densities and average ion mass in the plasmasphere and plasmatrough, near the Earth’s magnetic equator. These models are combined to provide an estimate of the most probable plasma mass density in the equatorial region. We then use machine learning to form a set of models which are parameterized by the SuperMAG ring current index (SMR) based on the design of the average models. The resulting set of models are capable of predicting the average ion mass, electron density and plasma mass density in the range and over all MLT sectors during a range of conditions where nT. This article is protected by copyright. All rights reserved.
Published by: Journal of Geophysical Research: Space Physics Published on: 08/2021
YEAR: 2021   DOI: https://doi.org/10.1029/2021JA029565
We conduct a statistical study on the sudden response of outer radiation belt electrons due to interplanetary (IP) shocks during the Van Allen Probes era, i.e., 2012 to 2015. Data from the Relativistic Electron-Proton Telescope instrument on board Van Allen Probes are used to investigate the highly relativistic electron response (E > 1.8 MeV) within the first few minutes after shock impact. We investigate the relationship of IP shock parameters, such as Mach number, with the highly relativistic electron response, including spectral properties and radial location of the shock-induced injection. We find that the driving solar wind structure of the shock does not affect occurrence for enhancement events, 25\% of IP shocks are associated with prompt energization, and 14\% are associated with MeV electron depletion. Parameters that represent IP shock strength are found to correlate best with highest levels of energization, suggesting that shock strength may play a key role in the severity of the enhancements. However, not every shock results in an enhancement, indicating that magnetospheric preconditioning may be required.
Published by: Geophysical Research Letters Published on: 12/2016
YEAR: 2016   DOI: 10.1002/2016GL071628
Trapped electrons in Earth\textquoterights outer Van Allen radiation belt are influenced profoundly by solar phenomena such as high-speed solar wind streams, coronal mass ejections (CME), and interplanetary (IP) shocks. In particular, strong IP shocks compress the magnetosphere suddenly and result in rapid energization of electrons within minutes. It is believed that the electric fields induced by the rapid change in the geomagnetic field are responsible for the energization. During the latter part of March 2015, a CME impact led to the most powerful geomagnetic storm (minimum Dst = -223 nT at 17 March, 23 UT) observed not only during the Van Allen Probe era but also the entire preceding decade. Magnetospheric response in the outer radiation belt eventually resulted in elevated levels of energized electrons. The CME itself was preceded by a strong IP shock whose immediate effects vis-a-vis electron energization were observed by sensors on board the Van Allen Probes. The comprehensive and high-quality data from the Van Allen Probes enable the determination of the location of the electron injection, timescales, and spectral aspects of the energized electrons. The observations clearly show that ultrarelativistic electrons with energies E > 6 MeV were injected deep into the magnetosphere at L ≈ 3 within about 2 min of the shock impact. However, electrons in the energy range of ≈250 keV to ≈900 keV showed no immediate response to the IP shock. Electric and magnetic fields resulting from the shock-driven compression complete the comprehensive set of observations that provide a full description of the near-instantaneous electron energization.
Kanekal, S.; Baker, D.; Fennell, J.; Jones, A.; Schiller, Q.; Richardson, I.; Li, X.; Turner, D.; Califf, S.; Claudepierre, S.; Wilson, L.; Jaynes, A.; Blake, J.; Reeves, G.; Spence, H.; Kletzing, C.; Wygant, J.;
Published by: Journal of Geophysical Research: Space Physics Published on: 08/2016
YEAR: 2016   DOI: 10.1002/2016JA022596
During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth.We present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both MagEIS and REPT instruments on the Van Allen Probes mission. Data from the MagEIS instrument establishes the behavior of lower energy (<1MeV) electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the EMFISIS instrument on board Van Allen Probes, SCM and FGM instruments onboard THEMIS, and the low altitude polar orbiting POES satellite. These observations suggest that, during this time period, both radial transport and local in-situ processes are involved in the energization of electrons. The energization attributable to radial diffusion is most clearly evident for the lower energy (<1MeV) electrons, while the effects of in-situ energization by interaction of chorus waves are prominent in the higher energy electrons.
Published by: Journal of Geophysical Research: Space Physics Published on: 09/2015
YEAR: 2015   DOI: 10.1002/2015JA021395