The "QSabcmxyz" catalog of solar flares
Introduction
Traditionally we use the ABCMX classification scale to characterize the
magnitudes of solar flares as seen in soft X-rays.
This derives from the GOES/XRS passband, 1-8 Å, which dates from the
actual dawn of the space age; many GOES spacecraft have contributed to what is
by now a very long and nominally uniform time series.
Here each letter represents a power of ten, and because there is a weak
correlation between flux and isothermal temperature, this letter string
is vaguely analogous to the classical astronomical sequence
OBAFGKM.
A better catalog?
But for several reasons, ABCMX is not an ideal framework. First, it only
covers five decades of brightness, and solar variability at 2-8 Å exceeds
that range; second, it is strongly biased because it measures the total solar
flux, rather than that due to the flare itself.
Furthermore, the top end of the ABCMX magnitude scale, has been hampered by
saturation effects in the top 12 events.
Accordingly, inspired by Ed Cliver's
suggestion "We can fix that!", we have extended the letter range to
include two decades at the bottom of the scale - termed Q and S
by the Sylwester group at Wrocław - and two at the top (y and z),
switching to lower-case letters to avoid confusion).
The second-from-the-top category (y) captures the
37 >X10 events
and class z makes room for Carrington-scale events when they may
eventually occur.
"QSabcmxyz" thus covers a dynamic range of 108, enough to
embrace both the quiet-Sun level and the greatest flare that the Sun
can muster.
The catalog
Click here
for the catalog listing (2 MB text file).
The S/B value (2 initially) is the minimum contrast required.
This reduced the total number from 48,131 to 42,469, leaving very few valid
b-class events, but retaining most of the c-class and above, as shown in
the table below.
| Class | Raw | Edited |
| Q | 3 | 0 |
| S | 6 | 0 |
| a | 34 | 0 |
| b | 4656 | 1904 |
| c | 36209 | 33400 |
| m | 6597 | 6539 |
| x | 589 | 589 |
| y | 37 | 37 |
| z | 0 | 0 |