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Journal of Geophysical Research Atmospheres
Article . 2012 . Peer-reviewed
License: Wiley Online Library User Agreement
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Global distribution of EMIC waves derived from THEMIS observations

Authors: Kyungguk Min; Jeongwoo Lee; Kunihiro Keika; Wen Li;

Global distribution of EMIC waves derived from THEMIS observations

Abstract

Electromagnetic ion cyclotron (EMIC) waves play an important role in magnetospheric dynamics and their global distribution has been of great interest. This paper presents the distribution of EMIC waves over a broader range than ever before, as enabled by observations with the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft from 2007 to 2010. Our major findings are: (1) There are two major peaks in the EMIC wave occurrence probability. One is at dusk and 8–12 RE where the helium band dominates the hydrogen band waves. The other is at dawn and 10–12 RE where the hydrogen band dominates the helium band waves. (2) In terms of wave spectral power the dusk events are stronger (≈10 nT2/Hz) than the dawn events (≈3 nT2/Hz). (3) The dawn waves have large normal angles (>45°) in the hydrogen band and even larger normal angles (>60°) in the helium band. The dusk waves have small normal angles (≤30°) in both the hydrogen and helium bands. (4) The hydrogen band waves at dawn are weakly left‐hand polarized near the equator, become linearly polarized with increasing latitude and eventually weakly right‐hand polarized at high latitudes whereas the helium band waves at dawn are linearly polarized at all latitudes. Dusk waves in both bands are strongly left‐hand polarized over a wide range of latitude. Based on the linear EMIC instability model presented by Horne and Thorne (1994), we suggest that the main underlying factor for the observed spatial variations of these wave properties would be local density of cold plasma and chemical abundance. In addition, the distinct properties of H and He band waves found in this study would deserve a new attention in relation to EMIC wave generation mechanisms.

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
232
Top 1%
Top 10%
Top 1%
bronze