Red Auroral Corona.

Few auroras show this level of detail. This unusual display of an auroral corona occurred on Earth three days after an unusual solar event -- the fifth most powerful explosion yet recorded on the Sun . An X14-class solar flare on April 15 sent a tremendous Coronal Mass Ejection (CME) into the Solar System. This CME did not directly impact the Earth . The Solar-System wide shock wave it created probably did, however, causing a G3-class geomagnetic storm and a night filled with colorful auroras across much of northern North America . The unusual red color of this Michigan aurora is caused by solar ions striking oxygen molecules 300 kilometers high in Earth's atmosphere . More typical green auroras are caused by oxygen recombining only 100 kilometers high.