[1] 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 À200 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.
The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations [1] We investigate the seasonal variation of the relation between SAPS (subauroral polarization streams) peak ion velocity and zonal wind velocity with coordinated DMSP and CHAMP satellite observations in both hemispheres, separately for Kp < 4 and Kp ≥ 4 geomagnetic conditions. Both SAPS and westward zonal wind peak almost at the same latitude. However, SAPS and zonal wind peak velocities show significantly different seasonal variations. SAPS peak velocities are larger in winter as compared to summer, while zonal wind peak velocities have opposite behavior, larger in summer and smaller in winter, which is valid in both hemispheres and for both geomagnetic activity levels. We reveal, for the first time, that SAPS peak westward ion fluxes, the product of SAPS ion velocity and ion density, exhibit similar seasonal variation as the zonal wind. The results indicate that the effect of SAPS on the zonal wind depends strongly on local ion densities. A linear relationship between SAPS ion fluxes and zonal wind is derived for both hemispheres, which is practically independent of geomagnetic activity. The scaling factor between ion flux and wind velocity is about the same in both hemispheres. Conversely, the background westward wind velocity (bias value in linear equation) is by about 100 m/s higher in the Northern than in the Southern Hemisphere. We attribute this difference to the effect of the large offset between geographic and magnetic poles in the Southern Hemisphere.Citation: Wang, H., H. Lühr, and S. Y. Ma (2012), The relation between subauroral polarization streams, westward ion fluxes, and zonal wind: Seasonal and hemispheric variations,
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