Unexpected G4 – Severe geomagnetic storm
A combination of factors led to unexpectedly strong geomagnetic storm levels on Thursday, March 23, and Friday, March 24, 2023. The storm reached G3 – Strong levels at 14:49 UTC on March 23 and escalated to G4 – Severe at 04:04 UTC on March 24. The precise cause of this geomagnetic storm is still under investigation, but it is possible that coronal mass ejections (CMEs) from March 20 to 21 played a role.
- This is the most intense geomagnetic storm in nearly 6 years.
- Geomagnetic storms of this intensity occur on average 100 times per solar cycle
Initially, SWPC predicted that the arrival of a co-rotating interaction region (CIR) ahead of a recurrent, negative polarity coronal hole high-speed stream (CH HSS) would disturb the geomagnetic field, leading to G1 – Minor conditions on March 23. This disturbance, along with nearby transients, was expected to produce G2 – Moderate conditions on March 24. However, contrary to predictions, the geomagnetic field exhibited G3 – Strong levels on March 23 and G4 – Severe early on March 24.
The unanticipated intensity of the geomagnetic storm may have resulted from a stealthy CME or a combination of events, including CMEs from March 20 and 21.
G3 – Strong geomagnetic storm potential impacts:
The area of impact is 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.
G4 – Severe geomagnetic storm impacts:
The area of impact is primarily poleward of 45 degrees Geomagnetic Latitude.
- Induced Currents – Possible widespread voltage control problems and some protective systems may mistakenly trip out key assets from the power grid. Induced pipeline currents intensify.
- Spacecraft – Systems may experience surface charging; increased drag on low earth orbit satellites, and tracking and orientation problems may occur.
- Navigation – Satellite navigation (GPS) degraded or inoperable for hours.
- Radio – HF (high frequency) radio propagation sporadic or blacked out.
- Aurora – Aurora may be seen as low as Alabama and northern California.
Auroras were seen and recorded as far south as Colorado and New Mexico, U.S.
Featured image credit: TW (stock)
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