The April 1997 CME

What happened

One of the best-studied early halo coronal mass ejections of the SOHO era, launched by a C6.8 flare and observed directly by SOHO's LASCO coronagraph and EIT imager at speeds estimated between roughly 880 and 1,115 km/s. Along with a similar CME earlier that January, this event became a key case study used to develop the modern understanding of how halo CMEs — the ones that appear to expand symmetrically around the Sun because they're headed toward or away from Earth — connect to the geomagnetic disturbances they cause on arrival.