Strong positive polarity CH HSS sparks G2 – Moderate geomagnetic storm

aurora forecast for 0838z september 4 2022 f

A strong positive polarity coronal hole high speed stream (CH HSS) sparked a G2 – Moderate geomagnetic storm on September 4, 2022. G1-Minor storms continued into September 5. An additional enhancement is possible by midday today due to the arrival of CME produced on September 2.

The solar wind environment was enhanced under strong positive polarity CH HSS influences in 24 hours to 00:30 UTC on September 5.1

Total field strength ranged from 5-12 nT, and the Bz component was mostly sustained southward reaching up to -12 nT.

Solar wind speeds increased from ~590 km/s to a peak near ~675 km/s before becoming sustained near ~650 km/s. Phi was predominantly in a positive solar sector.

charmap 2345z september 3 2022
RTSW 3 days to 0644z september 5 2022
RTSW 1 day to 0644z september 5 2022

Geomagnetic K-index of 5 (G1 – Minor geomagnetic storm) threshold was reached at 01:50 UTC, followed by the Geomagnetic K-index of 6 (G2 – Moderate) at 05:15 UTC.

G2 – Moderate geomagnetic storm 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.
swx-overview-small september 3 to 6 2022

The solar wind environment is expected to remain enhanced over September 5 under persistent positive polarity CH HSS influence, with an additional enhancement possible by midday on September 5 due to the arrival of coronal mass ejection (CME) produced on September 2.

The geomagnetic field will likely continue to reach G1 – Minor to G2 – Moderate levels today due to persistent CH HSS effects and a possible glancing blow from the September CME event.

Primarily unsettled conditions, with isolated active periods, are expected on September 6 and 7 under continued, yet slightly weakening, CH HSS effects.

Solar activity is expected to be low with a chance for M-class flares and a slight chance for X-flares on September 5. The activity is expected to decrease to a chance for low levels on September 6 and 7 following the exit of Region 3089.


1 Forecast Discussion – Issued: 2022 Sep 05 0030 UTC – Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center

Featured image credit: NOAA/SWPC


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