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Theoretical study of zonal differences of electron density at midlatitudes with GITM simulation
Author(s) -
Wang Hui,
Ridley Aaron J.,
Zhu Jie
Publication year - 2015
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020790
Subject(s) - middle latitudes , zonal and meridional , thermosphere , earth's magnetic field , atmospheric sciences , latitude , atmosphere (unit) , ionosphere , solar maximum , geology , climatology , environmental science , solar cycle , solar wind , meteorology , geophysics , physics , geodesy , magnetic field , quantum mechanics
This study investigated various physical processes responsible for the longitudinal modulation of electron density ( N e ) at midlatitudes by employing the global ionosphere‐thermosphere model (GITM). The good agreements between GITM outputs and CHAMP observations indicate that the model is a suitable tool to perform the theoretical study. Nine runs were carried out to determine the effects from geomagnetic field geometry, zonal wind, meridional wind, high‐latitude activity, migrating tides from the lower atmosphere, and solar illumination in quantitative ways. Distinct features were discussed as follows. It was crucial that the geomagnetic and geographical axes were offset for the development of the longitudinal difference of N e . The zonal wind contributes to about 80% of the fraction of the observed longitudinal dependence of N e . The meridional wind effect is out of phase with the zonal wind over North America and Southern Ocean regions, which trims the fraction of the longitudinal difference to 65%. Over the South Pacific Ocean, the nighttime N e maintains at a higher level because of in‐phase effects from both zonal and meridional winds. The solar illumination was important in the formation of the background longitudinal pattern of the electron density. The migrating tide from the lower atmosphere could enhance the longitudinal difference of N e by 15% over North America. Enhanced activities at high latitudes could alter the longitudinal pattern of N e by transporting thermospheric composition disturbances to midlatitudes.