Dynamics of the Tongue of Ionizations During the Geomagnetic Storm on September 7, 2015
Kedeng Zhang, Hui Wang, Jing Liu, Zhichao Zheng, Yangfan He, Jie Gao, Luyuan Sun, Yunfang Zhong
Abstract
Abstract The dynamic evolution of the double tongue of ionization (TOI) into a single TOI at 400 km altitude during the geomagnetic storm on September 7, 2015 was studied using the Defense Meteorological Satellite Program observations and Thermosphere Ionosphere Electrodynamic General Circulation model simulations. The double TOIs occurred in the presence of increased southward B z and weak positive B y , while the single TOI occurred in the presence of northward turning of B z and duskward turning of B y . In both double and single TOI events, the plasma at middle latitudes in the afternoon (prenoon) sector was greatly enhanced due to the local upward (upward) and zonal (meridional) E × B drift. The transition process is due to both the northward and duskward turning of interplanetary magnetic field (IMF). The northward turning of IMF B z weakens the storm enhanced density (SED) and the TOI in both afternoon and morning sectors, while the increasing duskward IMF B y strengthens the morning TOI.