CH HSS sparks G2 – Moderate geomagnetic storming

A stream of high-speed solar wind coming from a recurrent, polar-connected, positive-polarity coronal hole is affecting our planet today and causing geomagnetic storming. G1 – Minor geomagnetic storm levels were reached at 08:48 UTC and increased to G2 – Moderate levels at 20:24 UTC.

Over the past 36 hours, solar wind parameters were indicative of the onset of a Co-rotating Interaction Region (CIR) followed by a positive polarity coronal hole high speed stream (CH HSS). Solar wind speeds increased to near 560 km/s. Total field increased to 17 nT. The Bz component underwent several sustained southward deviations and reached a maximum southward value of -17 nT. The phi angle was variable until 05:00 UTC today, when it settled in a positive sector.

The solar wind environment is expected to remain enhanced through September 29 due to ongoing CH HSS effects. G2 – Moderate levels are likely on September 28 (50% chance). Primarily active levels, with a chance for G1 – G2 (Minor – Moderate) storm levels are expected on September 29.

Meanwhile, solar activity is low. Regions 2681 (Alpha) and 2682 (Alpha; ex-AR2673 – the source of 4 X-class solar flares during its last rotation) were relatively inactive over the past 24 hours and produced no significant flare activity. Solar activity is expected to be at very low levels with a chance for C-class flares through September 29.

The greater than 2 MeV electron flux was at normal levels and is expected to increase to high levels by the end of the UTC day with the onset of abovementioned CH HSS. Levels are expected to be high through September 29. The greater than 10 MeV proton flux was at background levels and is expected to remain like that over the next three days.

SWPC alerts, watches and warnings

Space Weather Message Code: ALTK06
Serial Number: 448
Issue Time: 2017 Sep 27 2024 UTC

ALERT: Geomagnetic K-index of 6
Threshold Reached: 2017 Sep27 2024 UTC
Synoptic Period: 1800-2100 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.

***

Space Weather Message Code: WARK06
Serial Number: 404
Issue Time: 2017 Sep 27 2013 UTC

WARNING: Geomagnetic K-Index of 6 expected
Valid From: 2017 Sep 27 2012 UTC
Valid To: 2017 Sep 28 0300 UTC
Warning Condition: Onset
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.

***

Space Weather Message Code: ALTK05
Serial Number: 1167
Issue Time: 2017 Sep 27 2011 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2017 Sep27 2010 UTC
Synoptic Period: 1800-2100 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: WATA30
Serial Number: 170
Issue Time: 2017 Sep 27 1947 UTC

WATCH: Geomagnetic Storm Category G2 Predicted

Highest Storm Level Predicted by Day:
Sep 28:  G2 (Moderate)   Sep 29:  G1 (Minor)   Sep 30:  None (Below G1)

THIS SUPERSEDES ANY/ALL PRIOR WATCHES IN EFFECT

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.

***

Space Weather Message Code: WARK04
Serial Number: 3330
Issue Time: 2017 Sep 27 1705 UTC

EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 3329
Valid From: 2017 Sep 27 0610 UTC
Now Valid Until: 2017 Sep 28 1200 UTC
Warning Condition: Persistence

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

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents – Weak power grid fluctuations can occur.
Aurora – Aurora may be visible at high latitudes such as Canada and Alaska.

***

Space Weather Message Code: WARK05
Serial Number: 1410
Issue Time: 2017 Sep 27 1705 UTC

EXTENDED WARNING: Geomagnetic K-index of 5 expected
Extension to Serial Number: 1409
Valid From: 2017 Sep 27 0749 UTC
Now Valid Until: 2017 Sep 28 0300 UTC
Warning Condition: Persistence

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: ALTK05
Serial Number: 1166
Issue Time: 2017 Sep 27 0848 UTC

ALERT: Geomagnetic K-index of 5
Threshold Reached: 2017 Sep 27 0848 UTC
Synoptic Period: 0600-0900 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: WARK05
Serial Number: 1409
Issue Time: 2017 Sep 27 0749 UTC

WARNING: Geomagnetic K-index of 5 expected
Valid From: 2017 Sep 27 0749 UTC
Valid To: 2017 Sep 27 1800 UTC
Warning Condition: Onset
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: WARK04
Serial Number: 3329
Issue Time: 2017 Sep 27 0745 UTC

EXTENDED WARNING: Geomagnetic K-index of 4 expected
Extension to Serial Number: 3328
Valid From: 2017 Sep 27 0610 UTC
Now Valid Until: 2017 Sep 27 2100 UTC
Warning Condition: Onset

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

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents – Weak power grid fluctuations can occur.
Aurora – Aurora may be visible at high latitudes such as Canada and Alaska.

***

Space Weather Message Code: ALTK04
Serial Number: 2006
Issue Time: 2017 Sep 27 0744 UTC

ALERT: Geomagnetic K-index of 4
Threshold Reached: 2017 Sep 27 0745 UTC
Synoptic Period: 0600-0900 UTC

Active Warning: Yes

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

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents – Weak power grid fluctuations can occur.
Aurora – Aurora may be visible at high latitudes such as Canada and Alaska.

***

Space Weather Message Code: WARK04
Serial Number: 3328
Issue Time: 2017 Sep 27 0611 UTC

WARNING: Geomagnetic K-index of 4 expected
Valid From: 2017 Sep 27 0610 UTC
Valid To: 2017 Sep 27 1500 UTC
Warning Condition: Onset

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

Potential Impacts: Area of impact primarily poleward of 65 degrees Geomagnetic Latitude.
Induced Currents – Weak power grid fluctuations can occur.
Aurora – Aurora may be visible at high latitudes such as Canada and Alaska.

Featured image: Aurora forecast model at 20:55 UTC, September 27, 2017. Credit: NOAA/SWPC