Strong Storm-effect behaviors of topside and bottom-side ionosphere
under low solar activity: Case study in the geomagnetic storm during
25-27 August 2018
Abstract
The 25-27 August geomagnetic storm was the third largest storm in 24th
solar cycle, which was a surprising space event that generated in the
background of very low solar activity. This study presents an overview
of temporal-spatial behaviors of ionospheric plasma irregularities as
functions of geographic longitude, latitude and altitude by ground-based
(GNSS receivers and ionosonde) instruments and space-borne (Swarm-A and
Swarm-B) satellites. The results not only reveal the enhanced equatorial
ionization anomaly (EIA) and hemispheric asymmetry over the
Asian-Australian and American sectors in a particular time, but also
discover the development of hemispheric asymmetric features of global
ROTI in the main and recovery phases. In addition, this storm also
triggered positive plasma irregularities in altitudes of 100 to 150km
near Auroral zone, and the changed ratio of bottom-side plasma
irregularities exceeded 250%, which has been cross validated by
multiple instrument and TIE-GCM’s simulation. Furthermore, the
thermospheric density ratio O/N2, equatorial electrojet
and vertical E×B drifts suffered from the storm largely, the equatorial
and mid-latitude plasma irregularities may be a combined action of
thermospheric composition change, equatorial electrojet and vertical E×B
drifts. Finally, the storm also induced positive Joule heating
irregularities in Auroral ionosphere in altitudes of 100 to 400km with a
maximum changed ratio of >200%, as well as the cross Polar
voltage enhanced to ~90kv. The Polar ionospheric
irregularities may be associated with the additional energy input
through the ways of particle precipitation, Joule heating and
ionospheric currents intensification.