Influence of the Auroral Electrojet and Oval on Mid-Latitude Thermospheric Temperatures and Meridional Winds

抄録

A large geomagnetic storm commenced at 00:00 UT in conjunction with a southward turning of the IMF on September 18, 1979. Ground-based measurements of the thermospheric temperatures and the meridional winds were made with a Fabry-Perot interferometer from Albany, New York. A meridian scanning multicolor photometer recorded a weak SAR-arc emission which reached a peak intensity of only 160R. Since the arc remained rather weak, the temperature enhancements within the arc were not noticeable and the meridional wind structure did not show any deviations. There was, however, a significant interruption in the development of the ring current between about 03:00 UT and 05:00 UT. But the growth phase re-emerged shortly after 05:00 UT, resulting in major changes in the auroral dynamics. The neutral temperatures showed general enhancements of 100K to 150K, consistent with the storm time conditions. The mean temperature was about 1324±164K. The meridional winds were directed equatorward and they ranged between 30m/s and 370m/s. Both the temperature and wind speed, as expected, decreased during the first half of the night, and then they showed a rapid and dramatic increase as several substorms occurred in rapid succession and the electrojet moved equatorward for the period between 05:00 and 10:00 UT. The maximum wind speed occurred some 40 minutes earlier than the occurrence of the maximum temperature, indicating that the temperatures and meridional winds in the mid-latitude thermosphere respond to substorm intensification in a different way.
Cross-correlation analysis showed that there is a strong correlation between the enhanced neutral temperature and a parameter (AE²/D), which represents a ratio between the energy input by the auroral electrojet activity and the distance between the point of observation and the location of the energy deposition. The correlation coefficient is nearly 0.84.