Athanasios Boudouridis

Statistical study of the effect of ULF fluctuations in the IMF on the cross polar cap potential drop for northward IMF

[1] Recent studies showed that, regardless of the orientation of the Interplanetary Magnetic Field (IMF), ULF wave activity in the solar wind can substantially enhance the convection in the high latitude ionosphere, suggesting that ULF fluctuations may also be an important contributor to the coupling of the solar wind to the magnetosphere‐ionosphere system. We conduct a statistical study to understand the effect of ULF power in the IMF on the cross polar cap potential, primarily focusing on northward IMF. We have analyzed the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) calculations of the polar cap potential, a IMF ULF index that is defined as the logarithm of Pc5 ULF power in IMF, and solar wind velocity and dynamic pressure for 249 days in 2003. We find that, separated from the effects of solar wind speed and dynamic pressure, the average cross polar cap potentials show a roughly linear dependence on the ULF index, with a partial correlation coefficient of 0.19. Highly structured convection flow patterns with a number of localized vortices are often observed under fluctuating northward IMF. For such a convection configuration, it is hard to estimate properly the cross polar cap potential drop, as the enhanced flows around the vortices that may be associated with IMF fluctuations do not necessarily yield a large potential drop. Thus, despite the relatively small correlation coefficient, the linear trend we found gives support to the significant role of IMF ULF fluctuations on the coupling of the solar wind to the magnetosphere‐ionosphere system.

Data assimilation of space-based and ground-based observations, and empirical models into a plasmasphere model

Summary form only given. The Earths plasmasphere is a region of dense plasma, originating in the ionosphere, extending nearly to geostationary orbit. The precise extent of the plasmasphere is dynamic, particularly during geomagnetic active conditions. Knowing the exact distribution of plasma in the plasmasphere is important as an input to coupled magnetospheric models. In particular, density gradients inside the plasmasphere and at the plasmapause, are important in controlling waves which are responsible for the growth and decay of the radiation belts. At the most basic level the plasmasphere can be described in terms of plasma exchange with the ionosphere and convection due to an imposed electric field. At that level plasmasphere modeling is relatively simple. However there is currently insufficient knowledge of the drivers, particularly the electric field, to model the plasmasphere boundaries at the most accurate level to provide sufficient quality inputs to wave and radiation belt models.