Tracking the energy input form the magnetosphere to the ionosphere-thermosphere system

Tuesday, 16 December 2014
Eftyhia Zesta, NASA Goddard Space Flight Center, Greenbelt, MD, United States, Hyunju Connor, NASA/GSFC, Greenbelt, MD, United States, Yong Shi, University of New Mexico, Albuquerque, NM, United States, Joachim Raeder, University of New Hampshire, Durham, NH, United States, Mariangel Fedrizzi, NOAA/SWPC-Univ. Colorado/CIRES, Boulder, CO, United States, Timothy J Fuller-Rowell, Univ of Colorado-CIRES, Boulder, CO, United States and Mihail Codrescu, SWPC/NOAA, Boulder, CO, United States
During geomagnetically active times, the ionosphere – thermosphere (IT) system is strongly affected by magnetospheric energy that comes in the form of auroral particle precipitation and Poynting flux. This ultimately results in the increase of the thermospheric mass density, a critical parameter not only for determining and predicting air drag on satellites, but also for understanding the solar wind - magnetosphere- IT coupling. We use observations and model simulations to explore when, where and how energy transfers from the solar wind through the magnetosphere and is deposited into the IT system during solar wind disturbances. We observe and simulate dynamic pressure impacts on the magnetosphere and a magnetic storm main phase. We use thermospheric density observations from the CHAMP and GRACE satellites and Poynting flux measurements from Defense Meteorological Satellite Platform (DMSP) satellites. We show that the thermosphere density as well as the downward Poynting flux intensified shortly after (within ~20 min) the sudden enhancement of the solar wind dynamic pressure mostly in the dayside auroral zone and polar cap regions with the peaks in the vicinity of the cusp. Simulations from the two-way coupled OpenGGCM-CTIM magnetosphere-ionosphere-thermosphere model show that the ionospheric Joule heating also increases abruptly along with the sudden enhancement of the dynamic pressure in the same regions. The modeling results show that the pair of high-latitude localized cusp field-aligned currents (FACs) are intensified and extended azimuthally as a result of the enhanced dayside high-latitude reconnection caused by the sudden increase of the solar wind dynamic pressure. They are likely the source of the enhanced Joule heating and the ensuing thermospheric heating in that region. We also look at the first hours of a magnetic storm main phase where the picture is significantly more complex, but Poynting flux and thermospheric density first enhance at polar latitudes within the same spatial region before the heating moves equatorward. We look for general trends of the correlation between Poynting flux and thermospheric heating with an initial superposed epoch analysis study.