Strong M8.7 solar flare erupts from Region 3435

m8.7 solar flare september 21 2023 sdo aia304 image 1251z

A strong solar flare measuring M8.7 erupted from Active Region 3435 at 12:54 UTC on September 21, 2023. The event started at 12:42 and ended at 13:02 UTC. This is the second M8+ solar flare since M8.2 at 14:11 UTC on September 20.

A coronal mass ejection (CME) was observed in coronagraph imagery at approximately 13:53 UTC. Initial modeling of this event indicates a hit at Earth by late on September 24.

Radio frequencies were forecast to be most degraded over eastern South America, Atlantic Ocean, western Europe, and most of Africa at the time of the flare.

Region 3435 (beta-delta) still has enough energy to produce strong to major eruptions and it’s rotating toward the center of the disk — Earth-directed CMEs are possible in the days ahead.

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m8.7 solar flare september 21 2023 sdo aia304 image 1251z full
Image credit: NASA SDO/304, Helioviewer, The Watchers. Acquired at 12:51 UTC on September 21, 2023
sunspots on september 21 2023
Sunspots on September 21, 2023. Credit: NASA SDO/HMI
drap 1257z september 21 2023 m8.7 solar flare

M8.2 solar flare on September 20 produced a CME first seen in SOHO LASCO C2 imagery at 15:05 UTC. Analysis and modeling of the event determined a possible glancing blow late on September 23 to early on September 24.

goes x-ray flux 1 minute september 21 2023

Solar activity is likely to be at moderate levels over the next three days, with a 55% chance of M-class and a 5% chance of X-class solar flares.

Influence from a negative polarity coronal hole (CH HSS) is likely to increase geomagnetic field conditions to active levels, with a chance for G1 -Minor storming periods on September 22.

Continued unsettled to active levels are likely on September 23 due to the combined persistent effects from the CH HSS and the possible glancing blow from the periphery of a CME that left the Sun on September 20.

You can follow space weather in near real-time using our redesigned SWX application at

Alerts, Watches and Warnings published by the SWPC as well as C+ solar flares are posted at (Twitter) and (Telegram).

Featured image: M8.7 solar flare on September 21, 2023. Credit: NASA SDO/AIA304

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