Earth-orbiting satellites have just detected an X1.3-class solar flare (March 30 @ 1737 UT). The source is active sunspot AR2975--the same sunspot that has already hurled at least two CMEs toward Earth this week. NASA's Solar Dynamics Observatory recorded the flare's extreme ultraviolet flash:

Radiation from the flare ionized the top of Earth's atmosphere, causing a shortwave radio blackout over the Americas. Here is a blackout map. Aviators, mariners, and ham radio operators may have noticed unusual propagation effects at frequencies below 30 MHz.

A CME is almost certainly emerging from the blast site. SOHO coronagraphs have not yet detected the cloud, but there is strong circumstantial evidence. For instance, the US Air Force has detected a Type II solar radio burst, a type of natural radio signal generated by CME shock waves. Also, NASA's Solar Dynamics Observatory has imaged a solar tsunami apparently generated by a CME leaving the sun's atmosphere.

Note: Subscribers to our Space Weather Alert Service received a text message about this X-flare while it was happening. Such prompt notifications allow ham radio operators, satellite managers, amateur astronomers and others to react to flares before they fade away. Solar flare alerts: SMS Text.