Active Sunspot Region 1429 Produces Sola
The ARRL Letter
March 8, 2012
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Active Sunspot Region 1429 Produces Solar Flares, Coronal Mass Ejections:
This week has been an active week for our Sun. An X-1.1 class solar
flare erupted from the Sun on March 4 at 11:13 PM EST (0413 UTC March
5), sending an explosion of plasma and charged particles -- a coronal
mass ejection (CME) -- hurtling through space. Forecasters at NOAA's
Space Weather Prediction Center are saying that this CME should miss
Earth, but it will hit Mercury and Venus. Then on March 6 at 7:28 PM
EST (0028 UTC March 7), the Sun released a solar flare, the strongest
one this year. The X-5 class flare hurled another CME into space, but
it is too soon to tell if this is an Earth-directed flare. This
activity is coming from sunspot 1429, which is currently making its way
around the northern hemisphere of the Sun.
Sunspot 1429 -- which emerged on the Sun on March 2 and is estimated to
be at least four to five times larger than Earth -- is slowly turning
to face Earth, so if any such eruptions do occur, they are increasingly
likely to be geoeffective.
When a CME hits the Earth's atmosphere -- approximately 72 hours
after exploding on the Sun -- the low bands will be depressed and
signals will be weaker the lower the frequency. The absorption rate
will be most severe on 160 meters, less on 80 and somewhat better on 40
meters. The maximum usable frequency (MUF) -- the highest frequency at
which a radio wave can propagate between given terminals by ionospheric
propagation alone, independent of power -- will be lower and auroral
propagation on the VHF bands is quite possible.
When aurorae occur, the electrons hit the ionosphere at the North and
South geomagnetic poles, creating ionization. Waves that would normally
travel off into space are bouncing off the aurora and being redirected
back toward Earth. This can create opportunities for long-distance
propagation via VHF and UHF. Read more here
The ARRL Letter
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