Glancing blow CME possible on July 23, G1 Geomagnetic Storm Watch

A glancing blow CME from the July 20 eruption could bring a chance for G1 – Minor geomagnetic storm condition on July 23, 2021. As a result, a G1 Geomagnetic Storm Watch is in effect.

A ~4-degree solar filament centered at approximately N25E65 erupted from the visible disk from 16:00 to 16:30 UTC on July 20. 

The disappearing solar filament (DSF) was associated with a B5-level enhancement at 16:33 UTC. Coronal mass ejection (CME) signatures were evident in available GOES-16 SUVI imagery.

STEREO-A imagery, as it became available, revealed a partial, northern favoring halo.

However, after further analysis and modeling by SWPC, initial results suggest a possible glancing blow later on July 23.

Space Weather Message Code: WATA20
Serial Number: 897
Issue Time: 2021 Jul 21 2029 UTC

WATCH: Geomagnetic Storm Category G1 Predicted
Highest Storm Level Predicted by Day:
Jul 22: None (Below G1) Jul 23: G1 (Minor) Jul 24: None (Below G1)
THIS SUPERSEDES ANY/ALL PRIOR WATCHES IN EFFECT
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 credit: NASA SDO/AIA 171