Hi,
AAVSO requests the help of amateur radio to monitore Sudden Ionospheric
Disturbances, aka SID in low bands

Extract from my website.
When the Sun release a CME of X-class, the D-layer see its ionisation level
increases drastically, absorbing all short frequencies. The result is a deep
fading of radio signals and shortly after a complete communications
black-out : these are sudden ionospheric disturbances, aka SID. This
phenomenon affects mainly VLF and low HF bands in degrading the MUF over
about half the Earth hemisphere, the one under the sunlight. Generally the
phenomeon occurs in the evening of at night and interrupts all
communications on VLF, 160 and 80 m bands. During periods of high
absorption, when geomagnetic storms occur, communications can be
interrupted on all HF spectrum, up to the 10 m band. The attenuation is
however limited to a few dB in the 20-10m band vs 20+ dB on 80m and
exceeding sometimes 40 dB on 160m !

If you are interested in this activity read
http://www.aavso.org/observing/programs/solar/sid.shtml

Thierry
ON4SKY, LX3SKY
http://www.astrosurf.com/lombry/qsl-perturbation2.htm