Southern pole connected CH HSS causes unsettled to major geomagnetic storms


Southern pole connected coronal hole high speed stream (CH HSS) is causing unsettled to major (G2 – Moderate) geomagnetic storms since April 15, 2015.

Geomagnetic K-index of 6 (G2 – Moderate) threshold was reached at 23:27 UTC on April 16, 2015.

During the last 12 hours (00:30 – 12:30 UTC on April 17) solar wind has maintained speeds of 600 to 750 km/s. Phi has been mostly negative (towards), total field oscillated between 10 nT and 4 nT while the Bz component was mostly negative and reached as low as -9 nT.

Space Weather Message Code: ALTK06
Serial Number: 338
Issue Time: 2015 Apr 16 2328 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2015 Apr 16 2327 UTC
Synoptic Period: 2100-2400 UTC
Active Warning: Yes
NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at

Potential Impacts: Area of impact primarily poleward of 55 degrees Geomagnetic Latitude.
Induced Currents - Power grid fluctuations can occur. High-latitude power systems may experience voltage alarms.
Spacecraft - Satellite orientation irregularities may occur; increased drag on low Earth-orbit satellites is possible.
Radio - HF (high frequency) radio propagation can fade at higher latitudes.
Aurora - Aurora may be seen as low as New York to Wisconsin to Washington state.

Conditions on April 18 and 19 should see wind speeds slowly decrease as the CH becomes less geoeffective, SWPC said.

The greater than 2 MeV electron flux at geosynchronous orbit was at moderate to high levels during last 12 hours and is expected to be at normal to high levels through April 17 -19.

The greater than 10 MeV proton flux at geosynchronous orbit was at background levels during last 12 hours. It is expected to remain at or near background conditions (Below S1 Minor).

SpaceWeather's Dr. Tony Phillips said the sustained encouter has sparked some of the brightest auroras of the year around the Arctic Circle. Rune Askeland sent this example from Bergen, Norway on April 17th:

Taken by Rune Askeland on April 17, 2015 @ Bergen, Norway (via SpaceWeather)

In the United States, Northern Lights have been sighted as far south as WashingtonMichiganMinnesota, and Idaho.


There are currently 5 numbered sunspot regions on the Earth side of the Sun.

Sunspots on April 17, 2015. Image credit: NASA SDO/HMI.

2321 – Beta-Gamma
2322 – Beta
2324 – Beta-Gamma
2325 – Beta
2326 – Beta

There is a chance for R1-R2 (Minor-Moderate) radio blackouts with a slight chance for an X-class flare (R3-Strong or greater) over the next three days (April 17-19).

Featured image: Taken by Rune Askeland on April 17, 2015 @ Bergen, Norway (via SpaceWeather)


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