July 14-16, 2000 Event: Polar Cap Size in Simulation and Ionospheric Image Data

Lutz Rastaetter
RITSS at Code 696/CCMC, NASA/GSFC

We use a BATSRUS MHD simulation of the July 14-16, 2000 (Bastille Day) event and trace magnetic field lines starting at the ionosphere in both hemispheres. Open field lines that end in the interplanetary field form the polar caps and are believed to be largely free of auroral emission features due to lack of particle precipitation. The field line tracings can show how accurately the MHD model reproduces the near-Earth magnetic topology as seen by the computed outline of the polar cap in the northern hemisphere with the satellite images. We use POAR and IMAGE photographs to compare the ion and electron emission regions with the computed polar cap outline.