The event comes just 4 days after X9.0 — thus far the strongest solar flare of Solar Cycle 25, also from Region 3842.
The event was associated with a 10cm Radio Burst (tenflare) lasting 4 minutes and with a peak flux of 640 sfu.
A 10cm radio burst indicates that the electromagnetic burst associated with a solar flare at the 10cm wavelength was double or greater than the initial 10cm radio background. This can be indicative of significant radio noise in association with a solar flare. This noise is generally short-lived but can cause interference for sensitive receivers including radar, GPS, and satellite communications.
At the time of press, there were no radio signatures that would suggest a coronal mass ejection (CME) was produced. Even if it was, the location of this region now close to the west limb does not favor Earth-directed CMEs.
Radio frequencies were forecast to be most degraded over the Pacific Ocean at the time of the flare.
Solar activity is expected to be moderate with 75% for M-class solar flares and 30% for isolated X-class flares through October 9.
The CME produced by the X9.0 solar flare on October 3 impacted Earth on October 6, producing G2 – Moderate geomagnetic storming.
The auroras spread across more than 20 U.S. states, including Alaska, Maine, Vermont, Minnesota, North Dakota, Washington, Wisconsin, New York, South Dakota, Idaho, Montana, Wyoming, Pennsylvania, Ohio, Illinois, Virginia, Kentucky, Missouri, Kansas, North Carolina, Mississippi, California.
The storm turned out to be significantly weaker than expected, and according to Dr. Tony Phillips of SpaceWeather it was ‘rescued by the autumnal Russell-McPherron effect.’ At this time of year, even weak CMEs can cause a geomagnetic storm.