The eruption, seen in this image below, is the strongest since September 2005.
In addition to the flare, a Coronal Mass Ejection accompanied the flare. A geomagnetic storm is a near certainty from this event, with G2 (Moderate) levels expected to start around 900 am EST Tuesday, continuing into Wednesday.
This could pose an impact to power grids, where voltage corrections may be required along with false alarms triggered on some protective devices. Intermittent satellite navigation and low-frequency radio navigation problems may occur.
With strong geomagnetic storms possible, high-latitude sky watchers should be alert for auroras.