Statistical Study of Magnetospheric Conditions for SAPS and SAID

Abstract

Inner-magnetospheric conditions for subauroral polarization streams (SAPS) and subauroral ion drifts (SAID) have been investigated statistically using Time History of Events and Macroscale Interactions during Substorms and RBSP observations. We found that plasma sheet electron fluxes at its earthward edge are larger for SAID than SAPS. The ring current ion flux for SAID formed a local maximum near SAID, but the ion flux for SAID was not necessarily larger than for SAPS. The median potential drop across SAID and SAPS is nearly the same, but the potential drop for intense SAID is substantially larger than that for SAPS. The plasmapause is sharper and electromagnetic waves were more intense for SAID. The SAID velocity peak does not strongly correlate with solar wind or geomagnetic indices. These results indicate that local plasma structures are more important for SAPS/SAID velocity characteristics as compared to global magnetospheric conditions.