Global energy-resolved X-ray images of northern aurora and their mappings to the equatorial magnetosphere

The Polar Ionospheric X-ray Imaging Experiment (PIXIE) on the GGS/Polar satellite provides global energy-resolved (2-60 keV) X-ray images of Earth from an apogee altitude ∼ 5 x 10 4 km. In the present study we analyze PIXIE data from the magnetic storm of 10-11 April 1997 (taken as prototypical). We show representative global X-ray images of the northern aurora, obtain representative spectra of the corresponding X-rays, measure (both globally and in hourly bins of magnetic local time) the radiated X-ray power corresponding to each image, extract optimal values for spectral parameters of the precipitating electrons that must have produced the X-rays, and calculate the effect of such precipitating electrons on height-integrated ionospheric Hall and Pedersen conductivities. Using representative global models of the magnetospheric B field, we map outstanding features of the auroral X-ray images along magnetic field lines to the equatorial magnetosphere in order to learn where the corresponding electrons must have resided immediately before precipitating. Finding that the most intense X-ray feature typically maps farthest out in the equatorial magnetosphere, we have used this feature (associated with an auroral arc or westward-traveling surge) to estimate the equatorial geocentric distance to the boundary between closed and open field lines in a model that treats this distance as an adjustable parameter.