Examining the contributions to the longitudinal variation of the low latitude upward ExB drift as simulated by TIME-GCM

Details Examining the contributions to the longitudinal variation of the low latitude upward ExB drift as simulated by TIME-GCM Examining the contributions to the longitudinal variation of the low latitude upward ExB drift as simulated by TIME-GCM

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa23a1784m&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SA23A-1784

Physics

[2411] Ionosphere / Electric Fields, [2415] Ionosphere / Equatorial Ionosphere, [2427] Ionosphere / Ionosphere/Atmosphere Interactions, [2447] Ionosphere / Modeling And Forecasting

Scientific paper

In the last several years space-borne observations of ionospheric and thermospheric densities as well as neutral winds have shown that there is a strong longitudinal variation even during geomagnetically quiet times. Studies have confirmed that many of these variations can be connected to the propagation of non-migrating tides which are excited in the troposphere. One mechanism to get the tidal signature from the lower thermosphere up to F-region altitude is via electrodynamic coupling due to wind driven current. It is therefore important to understand what is contributing to the longitudinal variation of the upward ExB drift at different local times. Sources of longitudinal variation include not only the neutral wind but also gravity-driven current, the geomagnetic field configuration and the conductivities. In this study we analyze the relative importance of these different sources using results from the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation model (TIME-GCM) forced by the Global Scale Wave Model (GSWM02) at the lower boundary (ca. 30 km). We focus on geomagnetic quiescent conditions. The model can reproduce part of the observed longitudinal variation. We find that the importance of the different sources strongly depends on the local time. As expected, the neutral winds below 120 km contribute the most to the longitudinal variation, but mainly during the day. However, even during the day neutral winds above 120 km are very important. The relative importance of zonal and meridional winds depends on the altitude and the local time. The upward drift at night is very sensitive to changes in the geomagnetic field configuration; however, this effect is minor during the day.

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