The Bastille Day Flare or Bastille Day Event was a powerful solar flare on July 14, 2000, occurring near the peak of the solar maximum in solar cycle 23. Active region 9077 produced an X5.7-class flare, which caused an S3 radiation storm on Earth fifteen minutes later as energetic protons bombarded the ionosphere. It was the biggest solar radiation event since 1989. The proton event was four times more intense than any previously recorded since the launches of SOHO in 1995 and ACE in 1997. The flare was followed by a full-halo coronal mass ejection and a geomagnetic super storm on July 15-16. The extreme level, G5, was peaked in late hours of July 15
The Bastille Day event was observed by Voyager I and Voyager II, thus it is the farthest out observed solar storm.
^ Webber, W. R., F. B. McDonald, J. A. Lockwood, and B. Heikkila (2002), The effect of the July 14, 2000 "Bastille Day" solar flare event on >70 MeV galactic cosmic rays observed at V1 and V2 in the distant heliosphere, Geophys. Res. Lett., 29, 10, 1377-1380, doi:10.1029/2002GL014729.