[HATS] Fwd: Severe storm - still!

[Ed Manuel]

Latest Solar Update.  If you are in North Texas, you should be looking for 
signs of Aurora - they saw it in northern New Mexico last time one this big 
hit!


>Gang,
>A severe geomagnetic storm remains ongoing at 2400UTC, although it is
>expected to start diminishing this evening.  It has caused near blackout
>conditions globally on the HF bands.  Todays estimated A-index is at
>least 50, with the K-indices since the onset being K=5,7,7 and 5.
>
>Yesterday morning (wednesday), there was a long duration flare event from
>an active region nearly at the sun's center.  It produced two M-class and
>a C-class flare, about 2-3 hours apart.  When a solar flare occurs, several
>things happen.  First is the "speed of light" radiation that leaves the
>sun and hits the earth for about the duration of the flare event ...
>which in this case was several hours.  This tends to ionize the E and F
>layers.  This is actually good, in that it emhances the reflectivity to
>radio waves for good skip propagation and low losses ... especially
>important to QRP operators.  So for a good hint, get on the higher
>frequencies shortly after a flare event to take advantage of several hours
>of some "hot" conditions on 10-15M, and sometimes 6M.
>
>But that bad thing about this ionizing radiation from a flare is if the
>radiation is strong enough, it will penetrate through the E and F layers
>and ionize the D-layer as well.  This is NOT good!  The D-layer is the
>"absorption layer" in that the more it is ionized from sunlight, the more
>attenuation it offers to HF signals.  So if the ionizing radiation from a
>flare were to highly ionize the D-layer, it would highly attenuate HF
>signals for very poor conditions (near blackout conditions) or even to a
>full blackout situation.  Fortunately, this usually only lasts for a short
>time (hours or less).
>
>Another thing that happens with a large flare, is to understand it is a
>huge explosion on the sun's surface, and as with any explosion, it produces
>a large shock wave.  The shockwave from a flare carries millions of tons of
>solar mass and tosses it out into space.  This is called a Coronal Mass
>Ejection or CME.  A CME is simply this shockwave of matter being flung out
>into space.  If the trajectory is right, then the shockwave will hit the
>earth.  Only about 20-30% of the CME's actually hit the earth.  For the
>shockwave to hit the earth, the CME must be originated from NEAR the center
>of the sun.
>
>Most shockwaves from flares travel towards the earth about 700-1200 km/sec.
>and thus takes about two days to get here.  When the shockwave does arrive,
>it is a very sudden, huge blast of solar wind smacking up against our
>magnetic field.  This causes our magnetic field to be compressed inward
>from the enhanced solar wind and starts it to wiggle like Jello.  As it
>wiggles, it generates huge electrical currents that flows along our magnetic
>field lines.  This is the dynamo effect, generating electricity by moving
>metal through a magnetic field ... or in this case, moving a magnetic
>field around stationary metal (which would be the earth itself, power lines,
>phone lines, YOUR ANTENNA, etc.).  This electrical current generates gobs
>of noise.  THIS IS THE BUZZING NOISE ON HF MANY OF YOU HAVE REPORTED HEARING.
>The earth's generator at work as our magnetic field is wiggling.
>
>In today's case, this gemagnetic storm is the result of the 3 large flares
>that occured yesterday, all from the same active region on the sun, and
>producing 3 separate and distinct CME's.  You can see these 3 CME's leaving
>the sun at:
>www.spaceweather.com
>A small video shows it on the home page, upper right corner.  Neat.
>
>So instead of the shockwave from a CME hitting the earth triggering a
>geomagnetic field, THREE CME's are smacking the earth, one behind the
>other, to keep our magnetic field wiggling pretty good.  Although to be
>fully accurate, the LASCO satellite detected only two shockwaves this
>morning, not three, meaning the velocity of the 3rd shockwave was likely
>less than the current solar wind at the time.  The first shockwave arrived
>about 1000UTC, bumping the solar wind up to about 600 km/sec.  Three hours
>later (1300UTC), the 2nd shockwave arrived, with a sudden increase in the
>solar wind to 1000 km/sec.  2-3 hours later, the background solar wind was
>still in the 700-800 km/sec range, likely masking the 3rd CME shockwave.
>
>This is a rare occurance, and nobody knows quite how to forecast it.
>Some believe the "3 shots across the bow" will keep the geomagnetic storm
>going all night.  Should this be the case, be on the lookout for AURORA
>THIS EVENING in the Northern U.S., and perhaps even well into the south.
>The K=7 suggests a fairly southern aurora ... but of course not down to
>Florida or Cuba or anything (sorry Arnie!).
>
>Others believe the signs are already here that the storm is subsiding,
>by the fact the K index has dropped from 7 to 5 over the last 3 hour
>reporting period.  This could mean the storm is winding down and aurora
>into the middle U.S. would be unlikely.
>
>The effects of a geomagnetic storm worsen the lower in frequency you go,
>so the upper bands, such as 10M if open, is scarcely effected, but 20M
>and below is pretty much wiped out.  So as the storm subsides, the upper
>bands will clear up first.  It takes VERY LITTLE storming to mess up 40M,
>for example :-(  as most of you have probably noticed.
>
>Anyway, that is a fairly short but hopefully succinct description of a
>solar storm, and the following geomagnetic storm, and a little of the
>physics behind it, for those of you new to QRP-L.
>
>For current conditions, see:  www.sec.noaa.gov/today.html
>
>The top of the page shows the current x-ray emissions from the sun, which
>indicate FLARE activity.  Right now that part is pretty quiet.  Below that
>is the earth environment, showing proton energy levels and the K-index.
>The elevated 10Mev Protons right now is giving our friends in Canada even
>a worse set of conditions that we have here, if you can believe that.
>And the K-index is shown on the bottom graph, updated every 3 hours.  RED
>bars indicate major storming (K=4) to severe storming (K5) to extreme
>storming (K=7,8,9).
>
>Geomagnetic storms are not the end of the world.  Turn the radio on now
>and again and check conditions.  Either you won't hear anything (severe
>storming/blackout), or very weak signals (major storming), or weird
>propagation.  The weird propagation means you can sometimes hear very
>distant DX stations quite loud, while everything else is kinda weak.  Hey,
>grab 'em while you can.
>
>Lastly, HF conditions tend to get very quiet and stable right after a
>large geomagnetic storm.  This is always a good time to get on the air,
>a day or two after a large storm, to take advantage of very quiet conditions
>and good DX propagation.  This could imply good conditions this weekend for
>the various contests.
>
>72, Paul NA5N
>
>National Radio Astronomy Observatory
>VLA/VLBA Radio Telescopes
>Socorro, New Mexico


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