Imaging of the Earth's Ring Current in Energetic Neutral Atoms

Donald Mitchell and the HENA Team

The IMAGE mission is the first of its kind. It is designed to
comprehensively image a variety of emissions from the Earth's magnetosphere
with sufficient time resolution to follow the dynamics associated with the
development of magnetospheric storms. This paper describes initial results
from the IMAGE High Energy Neutral Atom imager (HENA). HENA images at
energies between 10 and 60 keV/nucleon reveal the distribution and the
evolution of energetic ion distributions as they are injected into the ring
current during geomagnetic storms, drift about the Earth on both open and
closed drift paths, and decay through charge exchange to pre-storm levels.
Substorm ion injections are also imaged, as are the regions of low altitude,
high latitude ion precipitation into the upper atmosphere. Two qualitatively
different events are discussed, one a major magnetic storm (the "Bastille
Day" storm of July 15 and 16, 2000, Dst "300nT), and the other, a minor
storm (June 10, 2000, Dst ~-55nT). The large storm is characterized by ion
injection deep into the magnetosphere (L~3 RE), while the minor storm images
are consistent with injection to L~7 RE.

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Submitted to Geophysical Research Letters