Geomagnetic storming continues: G3 Strong levels reached on September 11

Geomagnetic storming continues: G3 Strong levels reached on September 11

Our planet's magnetic shield is again under stress today with brief G3 Strong geomagnetic storm levels reached around 09:00 UTC. The storms began on September 7 with positive polarity coronal hole reaching geoeffective position and an impact of plasma filament eruptions from September 4th and 5th. Aurora images we've seen over the last 4 days are astounding, be sure to check out some of them at the end of this article. 

Geomagnetic K-index of 5 (G1 Minor geomagnetic storm) threshold was first reached at 15:00 UTC on September 7. K-index of 6 (G2 Moderate) threshold was reached at 16:25 UTC that day.

With changing intensity, the storming continued until September 10, when K-index sharply dropped, and intensified again to 7 (G3 Strong) at 08:59 UTC on September 11. 

By 09:36 UTC today, this brief period of G3 Strong storm was over. However, enhanced geomagnetic activity is not over yet and we might experience more isolated periods of moderate to strong storming over the next couple of days.

According to SWPC's Forecast Discussion issued 00:30 UTC on September 11, the greater than 2 MeV electron flux was at normal to high levels over the last 24 hours, reaching a peak value of 3,170 pfu at 16:20 UTC on September 10. Throughout the same period, the greater than 10 MeV proton flux was background levels. The greater than 2 MeV electron flux is expected to reach high levels early September 11 before decreasing to normal levels mid-to-late September 11 through days September 12 - 13 due to the onset of enhanced geomagnetic activity.  The greater than 10 MeV proton flux is expected to persist at background levels.

Solar wind parameters remained slightly enhanced during the last 24 hours and reflected the transition between solar features.  Solar wind speeds varied between 370 - 453 km/s, IMF total field values ranged between 1-14 nT, and Bz reached a maximum southward deflection of -8 nT late September 10.  The phi angle began the period in a negative (toward the Sun) solar sector orientation but became variable after 11:00 UTC on September 10. 

Image credit: NOAA/SWPC

Solar wind parameters are expected to become further enhanced mid-to-late September 11 through early September 13 due to the onset of a recurrent positive polarity coronal hole high speed stream (CH HSS) in addition to the possible arrival of the September 7th Coronal Mass Ejection (CME). Recurrence data suggests wind speeds in excess of 550 km/s could be observed as the CH HSS moves into geoeffective position.

WSA-ENLIL solar wind prediction

High latitude skywatchers should remain alert for auroras.

SWPC alerts

Space Weather Message Code: ALTK07
Serial Number: 98
Issue Time: 2015 Sep 11 0859 UTC

ALERT: Geomagnetic K-index of 7
Threshold Reached: 2015 Sep 11 0859 UTC
Synoptic Period: 0600-0900 UTC

Active Warning: Yes
NOAA Scale: G3 - Strong

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 50 degrees Geomagnetic Latitude.
Induced Currents - Power system voltage irregularities possible, false alarms may be triggered on some protection devices.
Spacecraft - Systems may experience surface charging; increased drag on low Earth-orbit satellites and orientation problems may occur.
Navigation - Intermittent satellite navigation (GPS) problems, including loss-of-lock and increased range error may occur.
Radio - HF (high frequency) radio may be intermittent.
Aurora - Aurora may be seen as low as Pennsylvania to Iowa to Oregon.

***

Space Weather Message Code: ALTK05
Serial Number: 846
Issue Time: 2015 Sep 11 0936 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2015 Sep 11 0936 UTC
Synoptic Period: 0900-1200 UTC

Active Warning: Yes
NOAA Scale: G1 - Minor

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

Potential Impacts: Area of impact primarily poleward of 60 degrees Geomagnetic Latitude.
Induced Currents - Weak power grid fluctuations can occur.
Spacecraft - Minor impact on satellite operations possible.
Aurora - Aurora may be visible at high latitudes, i.e., northern tier of the U.S. such as northern Michigan and Maine.

***

Space Weather Message Code: ALTK06
Serial Number: 371
Issue Time: 2015 Sep 11 1001 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2015 Sep 11 1000 UTC
Synoptic Period: 0900-1200 UTC

Active Warning: Yes
NOAA Scale: G2 - Moderate

NOAA Space Weather Scale descriptions can be found at
www.swpc.noaa.gov/noaa-scales-explanation

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.

Aurora images since September 7

These are just some of the beautiful images captured since September 7:

Featured image: Southern lights taken by Minoru Yoneto on September 9, 2015 @ Queenstown, New Zealand. (via SpaceWeather)

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