Solar activity reached high levels on October 28, 2021, with a pair of M-class flares from geoeffective AR 2887 at 07:40 and 10:28 UTC, followed by a major X1.0 flare at 15:35 UTC which generated an Earth-directed coronal mass ejection (CME). As a result, a G3 – Strong geomagnetic storm watch is in effect for October 30.
A fast, asymmetric Halo CME was first observed in LASCO C2 imagery at 15:48 UTC, with CME impact at Earth expected early to mid October 30.1
A G3 – Strong geomagnetic storm watch is in effect for October 30 and G2 – Moderate for October 31.
Potential impacts (G3 – Strong):
(area of impact 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.
The greater than 10 MeV proton flux reached S1 – Minor radiation storm levels at 17:40 UTC. The greater than 100 MeV proton flux reached events levels at 16:35 UTC with a peak of 7.3 pfu at 18:15 UTC.
Solar radiation storms occur when a large-scale magnetic eruption, often causing a coronal mass ejection and associated solar flare, accelerates charged particles in the solar atmosphere to very high velocities.2
The most important particles are protons which can get accelerated to large fractions of the speed of light. At these velocities, the protons can traverse the 150 million km (93 million miles) from the Sun to Earth in just 10’s of minutes or less.
When they reach Earth, the fast-moving protons penetrate the magnetosphere that shields Earth from lower-energy charged particles. Once inside the magnetosphere, the particles are guided down the magnetic field lines and penetrate into the atmosphere near the north and south poles.
Solar Radiation Storms cause several impacts near Earth. When energetic protons collide with satellites or humans in space, they can penetrate deep into the object that they collide with and cause damage to electronic circuits or biological DNA.
During the more extreme Solar Radiation Storms, passengers and crew in high flying aircraft at high latitudes may be exposed to radiation risk. Also, when the energetic protons collide with the atmosphere, they ionize the atoms and molecules thus creating free electrons.
These electrons create a layer near the bottom of the ionosphere that can absorb High Frequency (HF) radio waves making radio communication difficult or impossible.
Space Weather Message Code: WATA50
Serial Number: 65
Issue Time: 2021 Oct 28 2216 UTC
WATCH: Geomagnetic Storm Category G3 Predicted
Highest Storm Level Predicted by Day:
Oct 29: None (Below G1) Oct 30: G3 (Strong) Oct 31: G2 (Moderate)
THIS SUPERSEDES ANY/ALL PRIOR WATCHES IN EFFECT
NOAA Space Weather Scale descriptions can be found at
Potential Impacts: Area of impact 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.
1 Major, long-duration X1.0 solar flare erupts from AR 2887, Earth-directed CME produced – The Watchers
2 Solar radiation storms – NOAA/SWPC
Featured image: CME produced by X1.0 solar flare on October 28, 2021. Credit: NASA/ESA SOHO LASCO C3
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