(excuse the off-disk dust particles!)
West is at the top - North on the left.
2005 Z - Tri-X afocal 40-mm eyepiece, 1/1000-sec exposure
The disk is dominated by Boulder Region 5395.
5395 N34 W04 2810 17 FKC 055 BGD
This translates into the region number, solar coordinates, area (in
millionths of a solar hemisphere), solar longitudinal extent, visual
classification (modified Zurich - McIntosh), spot count, and magnetic
classification (Mt. Wilson). The BGD denotes bipolar with opposite
umbrae polarities within a single penumbra - which give rise to high
magnetic gradients and thus flare potential. (Some twenty minutes after
this photo was taken it produced an M6 flare.)
An earlier X4/3B flare on Mar 10 was believed to have been the source for
the largest geomagnetic storm since 1960 that commenced three days later.
The Boulder A/K-indices for that event were: [00Z-21Z]
03-13-89 155 3 6 7 9 8 7 7 8
03-14-89 175 9 9 6 8 4 4 4 6
This group eventually maxed in size at 3600 on 17 March - but by then being
at W69 the foreshortening would have produced a much less spectacular view.
Page last updated March 31, 1998
