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Found 3 entries in the Bibliography.

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Propagation of EMIC Waves Inside the Plasmasphere: A Two-Event Study

Electromagnetic ion cyclotron (EMIC) waves are important for the loss of high-energy electrons in the radiation belt. Based on the measurements of Van Allen Probes, two events during the same storm period are presented to study the propagation of EMIC waves. In the first event, left-handed polarized EMIC waves were observed near the plasmapause, while right-handed waves were observed in the inner plasmasphere. The Poynting flux of the right-hand waves was mainly directed inward and equatorward, and no positive growth rates were obtained in the region of these right-hand waves, indicating the inward propagation of the waves from a higher L-shell. In the second event, the wave vectors were quasi-perpendicular to the background magnetic field inside the plasmaspheric plume but became quasi-parallel outside. This phenomenon can be explained by the refraction of the large density gradient, which qualitatively satisfies Snell\textquoterights law. These observations provide indirect evidence of the inward propagation of the EMIC waves and give a new insight on how density gradients may modify wave properties

Wang, G.; Zhang, T.; Gao, Z.; Wu, M; Wang, G.; Schmid, D.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2019

YEAR: 2019     DOI: 10.1029/2019JA027055

density gradient; EMIC wave; inward propagation; refraction; right hand polarization; Snell\textquoterights law; Van Allen Probes


Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

We present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA\textquoterights Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7\textendash9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from ~130 keV to >500 keV, with each dipolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.

Turner, D.; Fennell, J.; Blake, J.; Clemmons, J.; Mauk, B.; Cohen, I.; Jaynes, A.; Craft, J.; Wilder, F.; Baker, D.; Reeves, G.; Gershman, D.; Avanov, L.; Dorelli, J.; Giles, B.; Pollock, C.; Schmid, D.; Nakamura, R.; Strangeway, R.; Russell, C.; Artemyev, A.; Runov, A.; Angelopoulos, V.; Spence, H.; Torbert, R.; Burch, J.;

Published by: Geophysical Research Letters      Published on: 08/2016

YEAR: 2016     DOI: 10.1002/2016GL069691

energetic particle injections; magnetotail; Particle acceleration; plasma sheet; reconnection; substorm; Van Allen Probes

A telescopic and microscopic examination of acceleration in the June 2015 geomagnetic storm: Magnetospheric Multiscale and Van Allen Probes study of substorm particle injection

An active storm period in June 2015 showed that particle injection events seen sequentially by the four (Magnetospheric Multiscale) MMS spacecraft subsequently fed the enhancement of the outer radiation belt observed by Van Allen Probes mission sensors. Several episodes of significant southward interplanetary magnetic field along with a period of high solar wind speed (Vsw ≳ 500 km/s) on 22 June occurred following strong interplanetary shock wave impacts on the magnetosphere. Key events on 22 June 2015 show that the magnetosphere progressed through a sequence of energy-loading and stress-developing states until the entire system suddenly reconfigured at 19:32 UT. Energetic electrons, plasma, and magnetic fields measured by the four MMS spacecraft revealed clear dipolarization front characteristics. It was seen that magnetospheric substorm activity provided a \textquotedblleftseed\textquotedblright electron population as observed by MMS particle sensors as multiple injections and related enhancements in electron flux.

Baker, D.; Jaynes, A.; Turner, D.; Nakamura, R.; Schmid, D.; Mauk, B.; Cohen, I.; Fennell, J.; Blake, J.; Strangeway, R.; Russell, C.; Torbert, R.; Dorelli, J.; Gershman, D.; Giles, B.; Burch, J.;

Published by: Geophysical Research Letters      Published on: 06/2016

YEAR: 2016     DOI: 10.1002/grl.v43.1210.1002/2016GL069643

Magnetic reconnection; magnetospheres; Radiation belts; substorms; Van Allen Probes