ENA Images of Ring Current Ion Precipitation 14-24 April 2002

The High Energy Neutral Atom (HENA) camera on the IMAGE spacecraft images ion precipitation from the ring current through the upward ENA albedo of the downward ion precipitation. A newly developed ion/neutral transport theory predicts that an appreciable fraction of the incident ions will emerge from the exosphere (albeit at a lower energy due to inelastic collisions). These emerging intensities register dramatically in the HENA images during perigee passes, yielding about 6 images with excellent pixel statistics in each 2-minute exposure. The viewing aspect during the STORMS2002 period (14-24 April) was excellent at approximately 1500 km altitude over the southern polar cap. Almost the entire sub-auroral precipitation region falls within the images at some time during the passes. The emission from precipitation is also imaged at higher altitudes when IMAGE is between about N40^o-N60^o magnetic latitude, but at greatly reduced spatail resolution at the larger radial distances of 4-7 R_E. Our analysis techniques are still in the early stages of development, but even so, the ENA images can indicate when and where ring current precipitation is occurring. Thus they promise a new measure of geo-effectiveness of magnetic storm activity.