Bob posted:

Looks like that one went "past" the X portion of the scale

There are several classes of solar events which are rated in terms of their
X-ray output as well as their size (from the article OBSERVING THE SUN IN
H-ALPHA on the Prairie Astronomy Club's website):

Solar flares are ranked in importance by optical, X-ray, or radio flux.
Soft X-ray intensity is measured in the 1-8 Angstrom range monitored by the
GOES weather satellites. The classes are designated by the letters Bn
(n x 10-7 w/m2), Cn (n x 10-6 w/m2), Mn (n x 10-5 w/m2), or Xn (n x 10-4
w/m2), where n is the integer for each power of ten. Thus a flare classed as
M3 would produce a soft X-ray flux of .00003 watts per square meter.
Optically, flares are ranked by the area in square degrees of heliocentric
latitude they take up on the disk. A square degree at the center of the
solar disk is 12,147 km on a side, or at the sun's mean distance, each side
of the square would be about 17 seconds of arc across. The optical class
ranges from S (subflares) to 4 (largest).
AREA (sqr. deg) OPTICAL CLASS TYPICAL SOFT X-RAY CLASS
2.0 or less S (subflares) C2
2.1-5.1 1 M3
5.2-12.4 2 X1
12.5-24.7 3 X5
More than 24.7 4 X9
*A suffix (f, n, b) is added if the brightness is faint, normal, or bright,
based on a visual estimate.

This last flare was X17, so its X-ray output at peak was about 17 x 10^-4
watts per square meter, which is quite large (probably one of the largest seen
during this cycle). Again, some of the more impressive solar flares tend to
occur in the post-maximum part of the cycle. Clear skies to you.

--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************