Auroral X ray emissions observed by PIXIE during the September 24-25, 1998 storm

  S.M.Petrinec1, J.Mobilia1, D.L.Chenette1, W.L.Imhof1, and P. Chi2


1 Lockheed Martin Advanced Technology Center, Palo Alto, CA 94304

2 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095


In this study we examine the X ray emissions of the auroral regions as observed by the PIXIE imaging spectrometer on board the NASA/GGS POLAR satellite during the geomagnetic storm of September 24-25, 1998. PIXIE is capable of observing the entire northern auroral region at once in X rays. This geomagnetic storm was caused by a sudden compression of the solar wind plasma late on September 24, as observed by solar wind monitors. The interplanetary magnetic field increased in intensity, but did not turn significantly southward until a couple of hours after the compression front had passed. Prior to the passage of the sudden compression through the magnetosphere, there were weak auroral X ray emissions in localized regions of the northern aurora. With the passage of the sudden compression, the localized regions of X ray emissions increased dramatically in intensity, indicating that these regions represented the endpoints of preferred pathways for energetic electron precipitation at this time. We will examine the evolution of the X ray emissions (intensity and energy spectra) during this storm, inferring the characteristic electron energies and precipitated electron flux. In addition, we will compare and contrast the X ray emission patterns with data sets obtained from other ground-based and satellite instruments.