Wednesday, December 06, 2006

Stormy weather!

More from Paul Harden NA5N on QRP-L today:

Yesterday, the sun produced an X9 solar flare, *very* unusual for being near the bottom of the solar minimum. Today (6Dec) the sun produced another X6 flare. This certainly suggests that active region #0930 will be bringing us plenty of entertainment over the next two weeks as it rotates across the surface of the sun.

For the *duration* of the flare events, HF can be disrupted by bursty and continuum noise, plus enhanced D-layer ionization absorbing signals, if not a temporary HF blackout. However, once that bleeds off in an hour or two, the D-layer will be back to normal and the E/F layers will remain ionized above normal for the rest of your local daytime hours. This of course makes the E/F layers more reflective and raises the MUF. Therefore, a good time for QRPers to check the bands is an hour or so after a large flare until local sundown for enhanced HF propagation.

Most of today we've also been in a major geomagnetic storm. Believe it or not, it has nothing to do with yesterday's X9 (or today's X6) flare. The Earth has simply run in to a high speed electron stream from a coronal hole. This has exerted pressure against our magnetic field, compressing it, and generating huge electrical currents causing high HF noise levels. This will subside by later in the day.

If the sun produces M or X class flares over the next few days, the coronal mass ejection (CME) will begin to be pointed towards earth, meaning we can expect a geomagnetic storm about two days following the flare event. The closer the solar flare is to the center of the sun, more the direct of a hit we'll receive on earth. Today's X6, being near the limb of the sun, will probably give the earth only a glancing blow for a few hours of unsettled conditions late Friday.

The >10MeV proton count is high. These protons tend to accumulate in the polar regions (where the Earth's magnetic field is weakest). This causes a Polar Cap Absorption Event, meaning high absorption to HF signals for those above 45-50 degrees latitude. These same protons are what fuels auroral displays. Those in the higher latitudes are experiencing aurora now.

The moral of the story for QRPers:
1) Don't let reports of solar flares, geomagnetic storms, CME's keep you
off the bands. Much of this is of short term duration.
2) Enhanced HF propagation, including sporaidic openings on 15, 10 and even
6M can occur after a major flare for the rest of the day until sundown.
3) This includes possible north-south dx propagation at sundown due to
gray-line propagation. (If you do work McMurdo Sound, you better make
the QSO a snappy one, though -hi).
Good luck and have fun on the bands. It's not nearly as bad as it appears. In fact, it really works in the QRPers favor.
72, Paul NA5N

Thank you, Paul! You make all this science more palatable by putting it into "laymen's terms".
You're a QRP treasure - no doubt!

73 de Larry W2LJ

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