Proceedings with Extended Abstracts (single PDF file) - Radio ...

UPPER MESOSPHERE TEMPERATURE CHANGES OBSERVEDIN PMSE AND INCOHERENT SCATTER DURING A STRONGPOLAR CAP ABSORPTION EVENTK. Kubo 2 , J. Röttger 1 and S. Fukao 21Max-Planck-Institut, 37191 Katlenburg-Lindau, Germany2Radio Science Center for Space and Atmosphere, Uji, Kyoto, JapanMiddle of July 2000 an extremely strong solar proton event happened (named “Bastille II”),which caused major polar cap absorption (PCA) due to the strong increase of D-region electrondensity by high energy particle precipitation. The concurrent ionospheric disturbances led to enhancedelectric fields, which caused an increase of the ion drift and the neutral wind in the lowerthermosphere and possibly the upper mesosphere as well. Through the enhanced ion drag, increasesof ion and neutral temperature are usually resulting, which are also known as Jouleheating. We tried to recognize this in coherent scatter observations of PMSE with the SOUSYSvalbard Radar (SSR on 53.5 MHz) and observations of incoherent scatter with the EISCATSvalbard Radar (ESR on 500 MHz). We find two independent observations, which indicate apotential temperature increase of the upper mesopause region due to ion heating.During the strongest D-region electron density enhancement (i.e. increase of absorption) werecognized a disappearance of PMSE above 86 km lasting over a fraction of a day. This can beseen in Figure 1.Fig. 1 Five days of observations covering the Bastille II event. In the upperpanel the cosmic noise absorption on 53.5 MHz is shown. The two center panelsshow the K index of Tromsö in northern Norway and the planetary index K p ,respectively. The fourth panel from the top shows the signal strength of PMSEat 89 km, and the lower panel shows the HTI plot of PMSE over the full heightrange and period. The PMSE were observed with the SSR on 53.5 MHz.222