Paper#: 130
Poster #:
Session Name: Workshop 1C: High Latitude Processes
Room: West Ballroom
Day: Monday
Time: 5:10-5:35 p.m.
Abstract Title: Global X-Ray Observations of Auroral Disturbances
PresentSurname: Anderson, P.C.
All Authors: P.C. Anderson
Abstract : The Polar Ionospheric X-ray Imaging Experiment (PIXIE) on board NASA's Polar spacecraft provides global images of the auroral oval in X-rays for the long periods required to study substorm and stormtime activity. During periods of prolonged enhanced convection such as occur during geomagnetic storms, large disturbances are observed that are distinct from substorms as determined from auroral emissions, geosynchronous particle observations, and geomagnetic field measurements. These disturbances include substantial auroral emissions in the morning sector with little activity in the premidnight sector. They are associated with the earthward and dawnward drift of electrons caused by substantial cross-tail electric fields and magnetic field drift. Following substorm injections during geomagnetic storms, intense X-ray emissions are seen in the premidnight sector followed by intense emissions in the predawn hours that do not extend much past 9 - 10 MLT. However, during isolated substorms, the morningside emissions extend beyond 12 MLT with the most intense emissions occurring in the postdawn sector. These differences between stormtime and non-stormtime substorms are attributed to pitch-angle scattering mechanisms whose MLT distribution and intensity are dependent on the strength of the magnetospheric electric field which dominates particle convection during geomagnetic storms. There are also brief reductions in the intensity of the morningside emissions shortly after stormtime substorm onset consistent with a brief reduction in the cross-tail electric field, followed by intensification again in the predawn sector consonant with drifting electrons under the influence of a magnetospheric electric field.