Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 25, 2393-2403, 2007
https://doi.org/10.5194/angeo-25-2393-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
 
29 Nov 2007
Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations
H. Fujiwara1, R. Kataoka2, M. Suzuki1, S. Maeda3, S. Nozawa4, K. Hosokawa5, H. Fukunishi1, N. Sato6, and M. Lester7 1Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Japan
2RIKEN (The Institute of Physics and Chemical Research), Saitama, Japan
3Faculty for the Study of Contemporary Society, Kyoto Women's University, Kyoto, Japan
4Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
5The University of Electro-Communications, Tokyo, Japan
6National Institute of Polar Research, Tokyo, Japan
7Department of Physics and Astronomy, University of Leicester, Leicester, UK
Abstract. From simultaneous observations of the European incoherent scatter Svalbard radar (ESR) and the Cooperative UK Twin Located Auroral Sounding System (CUTLASS) Finland radar on 9 March 1999, we have derived the height distributions of the thermospheric heating rate at the F region height in association with electromagnetic energy inputs into the dayside polar cap/cusp region. The ESR and CUTLASS radar observations provide the ionospheric parameters with fine time-resolutions of a few minutes. Although the geomagnetic activity was rather moderate (Kp=3+~4), the electric field obtained from the ESR data sometimes shows values exceeding 40 mV/m. The estimated passive energy deposition rates are also larger than 150 W/kg in the upper thermosphere over the ESR site during the period of the enhanced electric field. In addition, enhancements of the Pedersen conductivity also contribute to heating the upper thermosphere, while there is only a small contribution for thermospheric heating from the direct particle heating due to soft particle precipitation in the dayside polar cap/cusp region. In the same period, the CUTLASS observations of the ion drift show the signature of poleward moving pulsed ionospheric flows with a recurrence rate of about 10–20 min. The estimated electromagnetic energy deposition rate shows the existence of the strong heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events.

Citation: Fujiwara, H., Kataoka, R., Suzuki, M., Maeda, S., Nozawa, S., Hosokawa, K., Fukunishi, H., Sato, N., and Lester, M.: Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations, Ann. Geophys., 25, 2393-2403, https://doi.org/10.5194/angeo-25-2393-2007, 2007.
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