Ionospheric characteristics associated with wave–particle interactions in a SED plume during a super geomagnetic storm

Abstract

We report some interesting ionospheric characteristics associated with wave–particle interactions with observations of the ionosonde and co-located incoherent scatter radar (ISR) at Millstone Hill in a storm-enhanced density (SED) plume identified from two-dimensional GPS TEC maps during a super geomagnetic storm on Nov. 20, 2003. Firstly, the digisonde ionogram only contained echoes for scanning frequencies from 6.2MHz to 9.3MHz. The lack of echoes at frequencies below 6.2MHz is attributed to enhancements of sub-ionospheric absorption caused by precipitating RC electrons in the SED plume. Secondly, there was an obvious F1 layer, as well as an Es layer, appearing on the ISR profile, that was not observed by the digisonde due to strong sub-ionospheric absorption. For echoes at frequencies from 6.2MHz to 9.3MHz, a comparison of the virtual height obtained from the digisonde ionogram and that derived from the ISR electron density profile, demonstrated that an Es layer appeared with a peak altitude of 123km. The occurrence of the Es layer is attributed to enhancements of precipitating energetic ion fluxes in the SED plume. Our result suggests that the ionospheric behavior in the SED plume is controlled not only by ionospheric dynamical process but also by precipitating energetic RC ions/ electrons as a consequence of wave–particle interactions in the plasmaspheric plume.