March 20, 2019: Northern spring began with a bang. On March 20th at 1118 UT, new sunspot AR2736 exploded, producing a C4-class solar flare that lasted more than an hour. The sunspot is inset in this image of the flare’s extreme ultraviolet flash:
The explosion sent minor waves of ionization rippling through Earth’s upper atmosphere and caused a shortwave radio “brownout” over southern parts of Europe and all of Africa. Anomalies in radio propagation at frequencies below 20 MHz might have been noticed by, e.g., mariners and ham radio operators.
The explosion also hurled a coronal mass ejection (CME) into space. NASA’s STEREO-A spacecraft saw the cloud racing away from the sun:
Additional images from the Solar and Heliospheric Observatory (SOHO) confirm that the CME is heading for Earth. While the bulk of the cloud appears set to miss our planet, the flanks of the CME should deliver a glancing blow. Estimated time of arrival: Late on March 22nd or sometime on March 23rd. NOAA forecasters favor the March 23rd estimate. Either way, moderate (G2) geomagnetic storms are possible when the CME arrives. Stay tuned for updates. Aurora alerts: SMS text, email.