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.

According to NOAA, G4-Severe geomagnetic storms occur about 100 times per one solar cycle (11 years).

WSA-Enlil CME model run at 15:23 UTC on June 21, 2015. Annotation: TW.

***

Space Weather Message Code: ALTK08
Serial Number: 21
Issue Time: 2015 Jun 22 1858 UTC

ALERT: Geomagnetic K-index of 8
Threshold Reached: 2015 Jun 22 1852 UTC
Synoptic Period: 1800-2100 UTC

Active Warning: Yes
NOAA Scale: G4 - Severe

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/NOAAscales

Potential Impacts: Area of impact primarily poleward of 45 degrees Geomagnetic Latitude.
Induced Currents - Possible widespread voltage control problems 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 - Aurora may be seen as low as Alabama and northern California.

***

Proton levels are still on the rise. Our planet is currently experiencing S3-Strong Solar Radiation Storm.

According to NOAA, there are about 10 such events per each solar cycle (11 years).

Space Weather Message Code: ALTPX3
Serial Number: 28
Issue Time: 2015 Jun 22 1912 UTC

ALERT: Proton Event 10MeV Integral Flux exceeded 1000pfu
Begin Time: 2015 Jun 22 1900 UTC
NOAA Scale: S3 - Strong

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/NOAAscales

Potential Impacts: Radiation - Passengers and crew in high latitude, high altitude flights may experience increasing radiation exposures. Astronauts on EVA (extra-vehicular activity) are exposed to elevated radiation levels.
Spacecraft - Single-event upsets to satellite operations, noise in imaging systems, and slight reduction of efficiency in solar panels are likely.
Radio - Degraded or episodically blacked-out polar HF (high frequency) radio propagation.

***

Update:

Another Earth-directed CME - M6.5

Active Region 2371, the source of two Earth-directed Coronal Mass Ejections (CMEs) over the past couple of days, produced an M6.5 solar flare (R2-Moderate) at 18:23 UTC on June 22, 2015. 

Associated with this event was a Castelli-U spectral burst including a 1000 sfu Tenflare and a Type II radio sweep (1480 km/s estimated shock velocity) indicating a CME was produced were associ

A full halo CME was produced, estimated time of arrival is June 24 at 23:00 UTC. 

Further analysis and subsequent models runs will be performed to better ascertain the intensity, timing, and duration of additional geomagnetic storm response from this latest CME. A G1 (Minor) Watch has been issued for June 24 and 25 as a preliminary response, SWPC said at 00:30 UTC on June 23.

Detailed M6.5 solar flare report is here.

Featured image credit: NOAA SWPC.

Geomagnetic storming reaching G4-Severe levels in progress