Three Coronal Mass Ejections (CMEs) produced on June 18, 19 and 21 have now all arrived at our planet and their combined effects caused G4-Strong geomagnetic storm on June 22, 2015.
Two of the three CMEs were produced by Region 2371, one of the biggest regions of the current solar cycle, which is currently directly facing Earth. This region has 'beta-gamma-delta' magnetic configuration and is capable of producing more strong to major eruptions on Sun. Due to its location, CMEs this region could produce over the coming days would most likely be Earth-directed.
Full-halo CME produced by a long duration M3.0 solar flare which erupted at 17:35 UTC on June 18 hit our planet at 16:50 UTC on June 21. It was a glancing blow followed by the arrival of partial-halo CME (produced by filament eruption in the SSE quadrant early June 19) at 05:45 UTC on June 22.
Direct hit by full-halo CME produced early June 21 was registered at 18:37 UTC.
Geomagnetic K-index of 8 (G4-Severe) threshold was reached at 18:52 UTC.
Area of impact is primarily poleward of 45 degrees Geomagnetic Latitude.
Under G4-Severe conditions, widespread voltage control problems are possible and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify.
Spacecraft - systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur.
Navigation - Satellite navigation (GPS) degraded or inoperable for hours.
Radio - HF (high frequency) radio propagation sporadic or blacked out.
Aurora may be seen as low as Alabama and northern California.
This is the very early stages of an event that will play out over many hours, with SWPC forecasting continuing storm level intensities into tomorrow. In Europe, watchers should be looking for the aurora now and there is hope for those over the US tonight, SWPC said.
In Addition: Another M class (M6) flare has erupted today from region 2371. This region is one of the largest in current solar cycle, it is very active, capable of producing more strong to major eruptions on the Sun and is currently located in perfect geoeffective position. If CME was generated by today's M6.5 event, it should be Earth-directed and add to already severely disturbed geomagnetic field.