Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere

Details Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsa32b..01w&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #SA32B-01

Physics

[2427] Ionosphere / Ionosphere/Atmosphere Interactions, [2431] Ionosphere / Ionosphere/Magnetosphere Interactions, [2443] Ionosphere / Midlatitude Ionosphere, [2788] Magnetospheric Physics / Magnetic Storms And Substorms

Scientific paper

The effects of cross-polar cap potential (CPCP) and subauroral flux tube-integrated conductivity on the spatial distribution of Subauroral Polarization Streams (SAPS) have been investigated by using DMSP observations. For higher flux tube-integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. 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 SAPS velocities for low integrated conductivity than for high conductivity. With coordinated CHAMP and DMSP observations we have further investigated the relationship between SAPS, ionospheric Hall current (electrojet), upper thermospheric zonal wind, and mass density at subauroral regions in the dusk and premidnight sectors. For comparison, we have also analyzed the same parameters as a function of magnetic latitude (30°-80° magnetic latitude) during nonSAPS periods. Both neutral and plasma velocities peak at the same latitude regardless of SAPS occurrence. The neutral wind during SAPS events gets enhanced by a factor of 1.5/1.2 for Kp<4 and 1.3/1.9 for Kp≥4 in the Northern/Southern Hemisphere, respectively, as compared to nonSAPS time. The velocity difference between plasma drift and neutral wind is also larger during SAPS period than during nonSAPS period, and the difference tends to increase with increasing geomagnetic activity. The peak latitude of the eastward auroral electrojet appears 1.5° poleward of SAPS during SAPS events, confirming the formation of SAPS equatorward of the high conductivity channel. The upper thermosphere is heated during SAPS periods. As a result we observe a 10% enhanced mass density at 400 km altitude with respect to periods without SAPS. In addition a density anomaly peak occurs collocated with the SAPS, displaced from the electrojet peak. We regard this as an indication for efficient thermospheric heating by ion neutral friction.

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