The main cause of geomagnetic activity this week will be a large coronal hole.

The Sun appears to be entering another two-week period of calm. Around mid-October, the star entered a peculiar cycle—two weeks of hyperactivity followed by two weeks of silence—and this pattern continues to hold. Currently, the rate of solar flares is rapidly declining: on December 10th, there were 23 flares in one day, 12 the next day, then 10, and last weekend, 8 and 5, respectively. Taking this simple sequence to its logical conclusion, we can assume that by Wednesday or Thursday, there will be no activity at all. A decline in activity is apparently also occurring on the far side of the Sun; at least, no signs of major explosions are observed there. Moreover, helioseismological methods, which, for better or worse, provide information on all major active regions on the Sun, see nothing of note on the far side, except for the giant sunspot complex 4294-4296-4298, which retreated there a couple of days ago and is now disintegrating before our eyes. However, even if this "Titanic" survives its upcoming two-week journey across the entire other side of the Sun, we won't know until the New Year.

The absolutely depressing picture of the solar winter in the coming days will likely be somewhat relieved by a rather large, uniquely shaped coronal hole that has formed on the solar disk. On Friday and Saturday, this strange, two-winged structure already "grazed" the Earth with its first, shorter wing, triggering brief magnetic storms that peaked on the night of December 12th-13th. A disturbed solar wind stream from the second, more extended wing will likely reach the Earth on Wednesday or Thursday. There is no forecast for magnetic storms yet, but since the previous encounter resulted in G1 storms, this can be considered a preliminary guide.

Overall, the week is expected to be calm. The main astronomical event of the coming week will undoubtedly be the closest approach to Earth of the interstellar object 3I/ATLAS, expected on Friday, December 19. It's hard to imagine the Sun being able to create a more powerful news event this week than this.