G2 – Moderate geomagnetic storm level reached

A G2 – Moderate geomagnetic storm conditions were reached at 04:33 UTC on April 20, 2017. This activity is a result of continued coronal hole effects, the first of two expected to affect our planet this week.

The geomagnetic field reached G1 – Minor levels during the 03:00 – 06:00 UTC synoptic period on April 19 due to brief elevated coronal hole high speed stream influences. Activity remained at quiet to unsettled conditions until 02:59 UTC on April 20 when G1 – Minor conditions were met again.

Geomagnetic K-index of 6 (G2 – Moderate geomagnetic storm) threshold was reached at 04:33 UTC. Under G2 conditions, the area of impact is primarily poleward of 55 degrees Geomagnetic Latitude. Power grid fluctuations can occur and high-latitude power systems may experience voltage alarms. Satellite orientation irregularities may occur as well as increased drag on low Earth-orbiting satellites. HF (high frequency) radio propagation can fade at higher latitudes. Aurora may be seen as low as New York to Wisconsin to Washington state.

The geomagnetic field is expected to remain elevated on April 20, with active conditions likely, due to residual effects from the positive polarity CH HSS. A likely decrease to unsettled conditions as the CH HSS conditions wane is expected on April 21 and 22.

SWPC Alerts

Space Weather Message Code: ALTK06
Serial Number: 427
Issue Time: 2017 Apr 20 0434 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2017 Apr 20 0433 UTC
Synoptic Period: 0300-0600 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.

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Space Weather Message Code: ALTK05
Serial Number: 1096
Issue Time: 2017 Apr 20 0337 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2017 Apr 20 0336 UTC
Synoptic Period: 0300-0600 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.

Featured image: Geoeffective coronal holes on April 19, 2017. Credit: NASA/AIA, LMSAL