Strong Magnetic Storm on 25-26 August 2018 with Reference to the Solar Cycle 24 Declining
Abstract
It is well known that the CIR (Corotating Interaction Region) driven magnetic storms are typical ones for a solar cycle declining but the CME (Coronal Mass Ejection) driven storms mostly appear during the solar cycle maximum. The CMEs rare occur during the solar cycle declining because they are associated with flares or filament eruptions, both of which are relatively rare in the low part of the cycle. However, in the Sun's downward cycle 24, all strong magnetic storms (e.g., in March, June and December 2015, May and September 2017) were caused by CMEs. The strong magnetic storm on 25-26 August 2018 (Dst = -171 nT) was the last storm of this series. In this case, the CME was associated with a filament eruption on 20 August under the very low solar wind speed. The comparison of two last sever magnetic storms (Sep2017 and Aug2018) showed that there is no linear relationship between the storm intensity (Dst index) and planetary geomagnetic activity (Ap index). So, the planetary geomagnetic disturbances in the Sep2017 storm were stronger than in the Aug2018 storm despite the fact that the Dst values in the first storm were smaller than in the second one. The solar cycle 24 continues to produce surprises. The cycle has not yet reached a minimum. Will be new magnetic storms or not?
- Publication:
-
Eleventh Workshop on Solar Influences on the Magnetosphere, Ionosphere and Atmosphere
- Pub Date:
- September 2019
- DOI:
- 10.31401/WS.2019.proc
- Bibcode:
- 2019simi.conf..107K