Geomagnetic storms of cycle 24 and their solar sources

Abstract

Abstract Solar activity of cycle 24 following the deep minimum between cycle 23 and cycle 24 is the weakest one since cycle 14 (1902–1913). Geomagnetic activity is also low in cycle 24. We show that this low geomagnetic activity is caused by the weak dawn-to-dusk solar wind electric field (E d–d) and that the occurrence rate of E d–d > 5 mV/m decreased in the interval from 2013 to 2014. We picked up seventeen geomagnetic storms with the minimum Dst index of less than −100 nT and identified their solar sources in cycle 24 (2009–2015). It is shown that the relatively slow coronal mass ejections contributed to the geomagnetic storms in cycle 24.

Keywords

• Geomagnetic storm
• Rising and maximum phases
• Two peaks
• Solar cycle 24
• Coronal mass ejection
• Coronal hole