Speaker
Description
The main drivers of geomagnetic storms are interplanetary coronal mass ejections (ICMEs) and solar wind high-speed streams (HSSs) with stream interaction regions (SIRs). In this presentation, we show one example of both cases and study their effects on the high-latitude ionosphere-thermosphere (I-T) system. We use a multi-instrument approach with ground-based instruments (e.g., the EISCAT Svalbard and Tromso incoherent scatter radars, GNSS TEC receivers, and magnetometers) as well as satellites (e.g., TIMED, Swarm, and GRACE-FO). The 10-13 May 2024 ICME driven storm was a superstorm (minimum SYM-H -518 nT), while the HSS/SIR drove only a moderate storm on 14-20 March 2016 (minimum SYM-H -69 nT). Both storms caused a depletion in F-region electron density and total electron content (TEC), increase in the ion temperature, and enhanced neutral density at the low-Earth orbit (LEO). While the changes during the May 2024 superstorm were more drastic than during the March 2016 storm, the duration of the changes was longer in the latter one. In the polar cap, 60% of the TEC disappeared during the whole day on 11 May 2024 and the depletion lasted to some extent 3 days, while in March 2016 the depletion in TEC lasted 6 days and was 25-50%. During the superstorm, LEO densities were increased by 300-500%, but in the moderate storm by 100%. The processes behind the I-T changes stem from increased Joule heating in the ionosphere, which we estimate for both storms with a new method utilizing data from SuperDARN radars, Ampere project field-aligned currents and SuperMAG magnetometers.
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