[K6BW] Type II Radio Emission (fwd)

[Bill Smith]

>From na5n at QRP-L.  The sun has been stirring recently, if barely wiggling.
Still, it is better than nothing!   On a similar note, is anyone interested
in Straight-key night New Year's Eve at Hamilton?   KPH will be on the air
(unless New-Year's Eve parties get in the way) on 3550 (80 meters CW) and
7040KHZ (40 meters CW).  It would be fun to establish contact.

Space Weather Message Code: ALTTP2
Serial Number: 693
Issue Time: 2009 Dec 22 0533 UTC

ALERT: Type II Radio Emission
Begin Time: 2009 Dec 22 0457 UTC
Estimated Velocity: 531 km/s

It's been so long since the sun produced even a measley Class C flare, I had
forgotten I was still subscribed to their alert service! I mean years.

Anyway, might be a small indication of things to come.  The alert contains a
couple pieces of interesting information.

First, it produced a Type II radio emission.  This is caused by the flare
hurling mass outward producing a shock wave.  As the shock wave travels away
from the sun, it punches through the sun's magnetic field lines, producing
radio bursts in the 100MHz region downward into HF.  Though the sun has had
a few small flares over the past couple of years, this is the first
producing a shock wave worthy of issuing an alert.  It is this shock wave,
if strong enough, that causes a geomagnetic storm on Earth 2-3 days later.
This one will not.

Secondly, the velocity of the shock wave was measured at 531 km/sec.
Roughly, the escape velocity of the sun is about 350 km/sec., so this shock
wave was sufficient to escape the sun.  It is now traveling along with the
solar wind through our solar system, another first in a long time (other
than caused by a coronal hole).

It takes a shock wave hitting the earth of about 600 km/sec. to produce even
a minor geomagnetic storm, so the effects of this will likely go completely
unnoticed.  Remember in the last solar cycle, major flares that caused major
geomagnetic storms?  Those shock waves were traveling well over 1,000
km/sec.  Today, the solar wind is right at 350 km/sec., or just barely above
the sun's escape velocity.  It doesn't get any quieter!

This Class C flare is mostly insignificant.  However, mixed with several
very small Class B flares and a couple of active regions over the past few
days, it could indicate "something is up" on the sun or perhaps it is
thinking about finally waking up.

For QRPers ... watch the sun over the next few days.  Even a handful of
small Class B and C flares may be sufficient to give our ionosphere a very
slight kick in the pants with a little extra ionizing radiation.  This might
be enough to open the higher bands for a while.  The time of interest would
be from the time of the flare until local sundown.

Yeah, yeah, grasping at straws here ... but it's as good of an opportunity
we've seen in a very long time.

My best wishes to you all for a Merry Christmas and a happy 2010.

72, Paul NA5N

73 de Bill, AB6MT