Aurora alert for December 23, after M-class flares
UPDATE DECEMBER 23, 2021, AT 16:45 UTC (8:00 AM EDT): NOAA/SWPC has refined its analysis of the CME from December 20th. Their new prediction is that the cloud of solar plasma and magnetic field will reach Earth late on December 23rd or early on the 24th. Their analysis indicates that most of the particles will pass south of Earth but they still are calling for a G1 geomagnetic storm. This should happen on December 24th. This will probably produce aurora for those at higher latitudes however people in regions like the northern US may see aurora on the horizon. Clear skies all you aurora watchers!
There’s been a small uptick in solar activity over the past two days (December 20 and 21, 2021). The increase comes from the fact that nine sunspot groups (active regions or AR) now pepper the visible face of the sun. Most solar flares – that is, storms on the sun – come from such regions. They often release streams of charged particles into space, called coronal mass ejections (CMEs). The CMEs take several days to travel across space to the Earth. When the solar charged particles in a CME strike Earth, they often cause beautiful displays of the aurora borealis and aurora australis (the northern and southern lights). These events also have the potential to affect power grids and satellites in Earth’s orbit.
At this time, effects from the December 20, 2021, solar storm are expected to arrive at Earth around December 23.
Multiple M-class solar flares
Three M-class solar flares occurred with their peak X-ray intensities at 11:36 UTC on December 20, 7:50 UTC on December 21, and 11:44 UTC on December 21. The flare on December 20 came from AR12908. The other two M-flares came from a region that hasn’t yet rotated into view on the east limb of the sun. Note that because the sun rises in the east for us, scientists label the limb of the sun that rotates into view, the left side, as east. All three flares produced radio blackouts for tens of minutes. Between these moderate-sized flares, lots of smaller C-class flares have been popping off.
SUNSPOT NUMBER RECORD: The official sunspot number (SIDC) just reached 130, the highest it has been during Solar Cycle 25. It has been above 100 for the last week, the longest sustained level for several years. Odd to think that just 10 days ago it was supposedly a spotless Sun. pic.twitter.com/ibuD4yO0r9
— Keith Strong (@drkstrong) December 21, 2021
Earth-directed CME triggered aurora alert
The flare on December 20 had a small-to-moderate CME associated with it. The forecast from NOAA’s Space Weather Prediction Center (SWPC) is for this CME to reach Earth around 21 UTC on December 23. NASA’s Moon to Mars Space Weather Office produced a model with a similar arrival time though slightly earlier of 16:28 UTC. This group has timing errors of roughly plus or minus 7 hours.
Possible auroras on December 23
This storm in Earth’s magnetosphere could create decent auroral activity on December 23, visible at the higher latitudes. Will the auroral activity extend down into the continential U.S.? We can’t answer that question at this time. Forecasts will be updated as we get closer to the CME’s expected arrival.
Bottom line: A solar storm has caused a stream of charged particles to be headed toward Earth. Aurora alert! Possible northern and southern lights on December 23, 2021.