Weak Magnetic Storms Can Modulate Ionosphere-Plasmasphere Interaction Significantly: Mechanisms and Manifestations at Mid-Latitudes Journal of Geophysical Research: Space Physics

A comprehensive study of the response of the ionosphere‐plasmasphere system at mid‐latitudes to weak (Dstmin > −50 nT) magnetic storms is presented. For the first time, it is shown that weak magnetic disturbances can lead to significant modulation of ionosphere‐plasmasphere H+ ion fluxes. It is found that this modulation is caused by the enhancements/reductions of the topside O+ ion density, which is induced by F2‐layer peak height rise and fall during the storms. The F2‐layer motion is caused by thermospheric wind changes and by a penetration electric field. Both drivers are closely related to the changes in the Bz component of interplanetary magnetic field. The most prominent manifestation of the H+ ion flux modulation is strong changes in H+ ion fraction in the topside ionosphere. This study also indicates that the NRLMSISE‐00 model provides the correct relative changes of neutral H density during weak magnetic storms and also that there is a compelling need to include geomagnetic activity indices, in addition to solar activity (F10.7), as input parameters to empirical topside ionosphere models.