Evolution of low‐altitude and ring current ENA emissions from a moderate magnetospheric storm: Continuous and simultaneous TWINS observations
Author(s) -
Valek P.,
Brandt P. C.,
Buzulukova N.,
Fok M.C.,
Goldstein J.,
McComas D. J.,
Perez J. D.,
Roelof E.,
Skoug R.
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010ja015429
Subject(s) - ring current , exosphere , magnetosphere , storm , energetic neutral atom , geomagnetic storm , physics , population , atmospheric sciences , orbiter , environmental science , ionosphere , ion , solar wind , meteorology , geophysics , astronomy , plasma , nuclear physics , demography , quantum mechanics , sociology
The moderate storm of 22 July 2009 is the largest measured during the extended solar minimum between December 2006 and March 2010. We present observations of this storm made by the two wide‐angle imaging neutral‐atom spectrometers (TWINS) mission. The TWINS mission measures energetic neutral atoms (ENAs) using sensors mounted on two separate spacecrafts. Because the two spacecrafts' orbital planes are significantly offset, the pair provides a nearly optimal combination of continuous magnetospheric observations from at least one of the TWINS platforms with several hours of simultaneous, dual‐platform viewing over each orbit. The ENA imaging study presented in this paper is the first reported magnetospheric storm for which both continuous coverage and stereoscopic imaging were available. Two populations of ENAs are observed during this storm. The first are emissions from the ring current and come from a parent population of trapped ions in the inner magnetosphere. The second, low‐altitude emissions (LAEs), are the result of precipitating ions which undergo multiple charge exchange and stripping collisions with the oxygen exosphere. The temporal evolution of this storm shows that the LAEs begin earlier and are the brightest emissions seen during the main phase, while later, during the recovery, the LAE is only as bright as the bulk ring current emissions.