  We report on the solar source of the 2022 February 3 geomagnetic storm of
moderate strength that contributed to the loss of 39 Starlink satellites. The
geomagnetic storm was caused by the 2022 January 29 halo coronal mass ejection
(CME) that was of moderate speed (about 690 km/s) originating from NOAA active
region 12936 located in the northeast quadrant (N18E06) of the Sun. The
eruption was marked by an M1.1 flare, which started at 22:45 UT, peaked at
23:32 UT on January 29 and ended at 00:24 UT the next day. The CME ended up as
a shock-driving magnetic cloud (MC) observed at Sun-Earth L1 and at
STEREO-Ahead (STA) located about 34 deg behind Earth. The geomagnetic storm was
caused by a strong southward component of the MC that was boosted by a high
speed solar wind stream behind the MC. Even though Earth and STA were separated
by only about 34 deg, the MC appeared quite different at Earth and L1. One
possibility is that the MC was writhed reflecting the curved neutral line at
the Sun. In-situ observations suggest that the MC was heading closer to STA
than to Earth because of the earlier arrival at STA. However, the shock arrived
at STA and Earth around the same time, suggesting a weaker shock at Earth due
to flank passage.
