Analyzing the Location of the Ion Convection Reversal Boundary in Polar Regions using DMSP Satellite Data

Measurements from the Defense Meteorological Satellite Program's (DMSP) F13 Satellite were used for a study of convection location in the polar regions of the earth's ionosphere. The satellite was in a sun-synchronous orbit in the dawn-dusk meridian. The data available corresponded to 4 second averages. Using a 20-second smoothing technique, the zero crossings in the ion drift velocity values were determined for each pass of the satellite. OMNI data were used to calculate the average IMF conditions for each pass from 5 minute data with a 10 minute lag to allow the IMF signal to propagate to the ionosphere. This study only considered passes with a Bz southward component where By was smaller than the Bz component. The location of the convection reversal boundary (CRB), or zero crossing in ion drift velocity, was archived for each Bz negative pass. This survey was conducted over the lifetime of the F13 satellite (1995-2009). The Weimer 2005 model was run under the same geophysical conditions in order to compare these models with the satellite observations. Model estimates of the CRB, or the location of the minimum and maximum electric potentials, were considered 'good' if they fell within 2 degrees of the 20-second observations, where 20 seconds corresponds to 1.176 degrees at 850 km. Preliminary results suggest that the model CRBs are 'good' about 65% of the time under Bz negative conditions. The model had a tendency to place the convection reversal boundary too far towards the pole, and showed higher accuracy levels on the dawn side of the earth than on the dusk side.