open access

https://hdl.handle.net/2115/49500

Correlation between electron density and temperature in the topside ionosphere

英語

2011-12-31

American Geophysical Union

Journal of Geophysical Research, Space Physics

116

A12331

The correlation between the electron temperature (Te) and electron density (Ne) at 600 km height at magnetic dip latitudes (MLat) less than about ± 40° measured by the Hinotori satellite from February 1981 to June 1982 is presented. The results show the well-known negative correlation between daytime Ne and Te when Ne is low. However, when the daytime Ne is significantly high (>10^[6] cm^[-3]), the correlation turns positive irrespective of latitude, longitude, season, solar flux levels, and magnetic activity levels. The positive correlation is most clear during 1100-1500 local time and around the magnetic dip equator (|MLat| < 10°) where high values of Ne with high Te are most abundant. Te also increases with increasing MLat in the same Ne range. Since the cooling through Coulomb collisions increases with the increase of Ne, the results suggest that an additional heat source(s) is involved for the positive correlation between Ne and Te. The additional heat source seems to be related to the integrated Ne along the magnetic field lines from the ground to 600 km altitude in one hemisphere, which is found to decrease with increasing MLat. Although the mechanism for the positive correlation is not well understood, the results imply that the Te in the topside ionosphere is controlled more by the integrated Ne than by in situ Ne or F2 peak Ne.

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Copyright 2011 by the American Geophysical Union

0148-0227