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Found 3 entries in the Bibliography.

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The First Observation of N+ Electromagnetic Ion Cyclotron Waves

Abstract Observations from past space missions report on the significant abundance of N+, in addition to those of O+, outflowing from the terrestrial ionosphere and populating the near-Earth region. However, instruments on board current space missions lack the mass resolution to distinguish between the two, and often the role of N+ in regulating the magnetosphere dynamics, is lumped together with that of O+ ions. For instance, our understanding regarding the role of electromagnetic ion cyclotron (EMIC) waves in controlling the loss and acceleration of radiation belt electrons and ring current ions has been based on the contribution of He+ and O+ ions only. We report the first observations by Van Allen Probes of linearly polarized N+ EMIC waves, which confirm the presence of N+ in the terrestrial magnetosphere, and open up new avenues to particle energization, loss, and transport mechanisms, based on the altered magnetospheric plasma composition.

Bashir, Fraz; Ilie, Raluca;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2021

YEAR: 2021     DOI:

electromagnetic ion cyclotron waves; heavy ions; Van Allen Probes; N+ EMIC Wave; Wave-particle interaction; inner magnetosphere


Variation in crossover frequency of EMIC waves in plasmasphere estimated from ion cyclotron whistler waves observed by Van Allen Probe A

We report variations in the propagation of the H+ band ion cyclotron whistlers observed by Van Allen Probe A. Ion cyclotron whistlers are one of the EMIC (electromagnetic ion cyclotron) waves generated by mode conversion from lightning whistlers. Crossover frequency is an important frequency for the ion cyclotron whistlers, which is a function of the variations in the local heavy-ion composition. We surveyed waveform data obtained by the Electric and Magnetic Field Instrument and Integrated Science instrument and found that 3461 H+ band ion cyclotron whistlers were observed from 572 km to 5992 km in altitude. The main finding is that the crossover frequencies of the observed events decreased with increasing altitude. These results support the hypothesis that the total heavy-ion density decreases with increasing altitude. Furthermore, in 96\% of all observed events, the crossover frequencies exceeded inline image, which suggests that the EMIC dispersion relation contains a frequency gap of around inline image.

Matsuda, Shoya; Kasahara, Yoshiya; Kletzing, Craig;

Published by: Geophysical Research Letters      Published on: 01/2016

YEAR: 2016     DOI: 10.1002/2015GL066893

EMIC wave; ion cyclotron whistler; plasmasphere; heavy ions; Van Allen Probes


Heavy-ion dominance near Cluster perigees

Time periods in which heavy ions dominate over H+ in the energy range of 1-40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L-values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L-values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy-ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet during quiet times. The drift time to these locations from the plasma sheet is > 30 hours, so that charge exchange has a significant impact on the population. We show that a simple drift/loss model can explain the dependence on L-shell and MLT of these heavy-ion-dominant time periods.

Ferradas, C.; Zhang, J.-C.; Kistler, L.; Spence, H.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2015

YEAR: 2015     DOI: 10.1002/2015JA021063

charge exchange; Cluster; heavy ions; inner magnetosphere; plasma sheet; ring current