Statistical study of the subauroral polarization stream: Its dependence on the cross-polar cap potential and subauroral conductance

Abstract

Two years of DMSP ion drift meter measurements have been used for a focused study of the subauroral polarization streams (SAPS). The main emphasis is on the effects of the cross-polar cap potential (CPCP) and the subauroral flux tube-integrated conductivity (that is, whether or not the northern and/or southern ionospheric footprint of the flux tube is sunlit or not) on the SAPS spatial distribution. For higher flux tube-integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. The magnetic latitude (MLAT) difference can reach several degrees at most. The dependence of SAPS location on geomagnetic activity is also studied, and it is found that the SAPS magnetic latitude exhibits an exponential relation with Dst. When Dst ≤ -200 nT the SAPS tend to occur at 48° MLAT. The CPCP averaged over 15 min prior to the SAPS correlates best with the SAPS peak velocities. The high-latitude CPCP has a stronger effect on the SAPS velocities for low integrated conductivity than for high conductivity. Finally, the observations show that there is a good anticorrelation between the subauroral integrated conductivity and the SAPS velocity, which confirms previous model results. Copyright 2008 by the American Geophysical Union.