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Ann. Geophys., 20, 1415-1427, 2002
www.ann-geophys.net/20/1415/2002/
© European Geosciences Union 2002
Ion and neutral temperature distributions in the E-region observed by the EISCAT Tromsø and Svalbard radars
S. Maeda1, S. Nozawa2, M. Sugino2, H. Fujiwara3, and M. Suzuki3
1Faculty for the Study of Contemporary Society, Kyoto Women’s University, Higashiyama-ku, Kyoto 605-8501, Japan
2Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
3Department of Geophysics, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
Correspondence to: S. Maeda (smaeda@kyoto-wu.ac.jp)
Abstract. Simultaneous Common
Program Two experiments by the EISCAT UHF radar at Tromsø and the EISCAT
Svalbard radar at Longyearbyen from 00:00 to 15:00 UT on 22 September 1998 and
9 March 1999 have been utilized to investigate distributions of the ion and
neutral temperatures in the E-region between 105 and 115 km. During the
experiments, soft particle precipitations in the dayside cusp were observed
over the Svalbard radar site by the Defense Meteorological Satellite Program (DMSP)
F11 satellite. It is found that the dayside electric field in the regions of
the low-latitude boundary of the polar cap and the cusp was greater and more
variable than that in the auroral region. The ion temperature, parallel to the
geomagnetic field at Longyearbyen, was higher than that at Tromsø during the
daytime from 06:00 to 12:00 UT. The steady-state ion energy equation has been
applied to derive neutral temperature under the assumption of no significant
heat transport and viscous heating. The estimated neutral temperature at
Longyearbyen was also higher than that at Tromsø. The ion and neutral energy
budget was discussed in terms of the ion frictional heating and the Joule
heating. The results indicate two possibilities: either the neutral temperature
was high in the low latitude boundary of the polar cap and the cusp, or the
heat transport by the polar cap neutral winds toward the dayside sector was
significant.
Key words. Ionosphere (auroral
ionosphere; ionosphere–atmosphere interactions; polar ionosphere)
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