Active sunspot AR3213 exploded during the early hours of Feb 10th (0303 UT), producing an M3.7-class solar flare and a shock wave in the sun’s atmosphere. This extreme ultraviolet movie from NASA’s Solar Dynamics Observatory shows what happened:
The shock wave is the shadowy disturbance expanding radially from the blast site. Based on the drift rate of a Type II solar radio burst reported by the US Air Force, the shock speed was 820 km/s (1.8 million mph).
Update: Shock waves like these usually lift a CME out of the sun’s atmosphere. In this case, however, no CME was detected by SOHO coronagraphs. Without a CME to rattle Earth’s magnetic field, the event will not cause a geomagnetic storm.
Ydun Ritz (2023-02-11)