Ion and neutral temperature distributions in the E-region observed by the EISCAT Tromsø and Svalbard radars

Abstract

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 lowlatitude 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.

Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations

“…The interplanetary magnetic field (IMF) B y and B z components were predominantly negative for this period. Although the variations of the IMF and the geomagnetic field in this period were already shown (Maeda et al, 2002;2005), the variations are shown again in Fig. 1.…”

“…In the present study, we use the EISCAT Common Program 2 (CP-2) mode version L data obtained in the period of 06:00-12:00 UT on 9 March 1999. Some of the data were already presented by Maeda et al (2002Maeda et al ( , 2005. The details of the ESR observation and the method for derivation of the ionospheric parameters are described in these papers.…”

“…Maeda et al (2002Maeda et al ( , 2005 showed that the dayside E region ion and neutral temperatures at Longyearbyen were higher than those at Tromsø with the European incoherent scatter (EISCAT) radars. They suggested the heat transport by the polar neutral winds in addition to Joule and/or auroral particle heating for causing the high temperatures in the polar cap/cusp E region.…”

Polar cap ionosphere and thermosphere during the solar minimum period: EISCAT Svalbard radar observations and GCM simulations

“…During the last decade, the variations, dynamical features, temperature and density structures in the polar cap and/or cusp region of the thermosphere/ionosphere have been clarified from radar and satellite observations (e.g., Innis and Conde, 2001;Maeda et al, 2002;Lühr et al, 2004;Liu et al, 2005;Fujiwara et al, 2007;Clemmons et al, 2008;Maeda et al, 2009, and references therein). In addition to recent works, Moe and Moe (2008) have reviewed historical studies on the high-latitude thermospheric mass density anomaly.…”

“…They showed thermospheric temperature variations at the F region height in the winter polar cap region during the solar minimum and maximum periods from Fabry-Perot interferometer measurements. Maeda et al (2002Maeda et al ( , 2009 showed ion temperature variations in the polar cap/cusp region from the European incoherent scatter (EISCAT) Svalbard radar (ESR) observations. Maeda et al (2009) found high-temperature regions in the flow channel of the polar cap ion-convection due to frictional heating near the fast ion flow channel.…”