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Regions of ion energization observed during the Galaxy‐15 substorm with TWINS
Author(s) -
Keesee A. M.,
Chen M. W.,
Scime E. E.,
Lui A. T. Y.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020466
Subject(s) - substorm , ion , physics , context (archaeology) , spectral line , magnetosphere , energetic neutral atom , plasma sheet , satellite , geomagnetic storm , astrophysics , plasma , geophysics , earth's magnetic field , magnetic field , geology , astronomy , paleontology , quantum mechanics
Ions in the plasma sheet are measured by the energetic neutral atom imagers on the Two Wide‐Angle Imaging Neutral‐Atom Spectrometers (TWINS) spacecraft. A line of sight (LOS) projection is used to determine the location of the ions that dominate the measured spectrum, assuming that the equatorial plane is the hottest region along the LOS. We verify reasonable agreement between ion spectral shapes measured using this remote measurement technique and in situ measurements from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft during two moderate geomagnetic storms. Conditions for reliable use of this technique to determine ion spectra and effective ion temperatures are identified. The technique is applied to the substorm interval associated with the loss of communication with the Galaxy‐15 satellite. During this interval, localized and broad regions of ion energization are observed, demonstrating that magnetic reconnection and current disruption may have played a role during this very extreme event. These observations demonstrate the ability of this technique to cast local ion spectra measurements in a global context.