The K7RA Solar Update

SEATTLE, WA, Dec 22, 2006 -- More stormy space weather showed up this week! At the same time, sunspot activity was lower. Average daily sunspot numbers dropped 17 points to 10.4 for December 14-20, but on December 15, the planetary A index -- an indicator of global geomagnetic activity from magnetometers around the globe -- rose to 104. That's a very high number and indicates a severe geomagnetic storm.

The cause was a large coronal mass ejection (CME) that happened to be Earth-directed. It arrived on December 14, and aurora borealis -- the northern lights -- were visible as far south as Arizona. During the hours of darkness in North America December 14 and 15, the planetary K index rose to eight for three successive three-hour periods. That's very big. For the next few weeks, you can view the numbers for that period on the Space Environment Center site.

Thanks to N7SO and N7TP for the tip on a paper presented last week in San Francisco at the fall 2006 meeting of the American Geophysical Union. The paper was titled "Geomagnetic activity indicates a large amplitude for sunspot cycle 24" and (abstract) (NASA news report).

The paper proposes that the next sunspot cycle could be one of the most intense cycles ever observed. The prediction technique uses geomagnetic activity during solar minimum to predict solar activity during the peak of the next cycle. But the geomagnetic activity used for this calculation isn't the dramatic sort that we've seen this week, but constant levels of solar wind streams that frequently affect the earth's magnetosphere. .

Another article concerning the upcoming Cycle 24 that you shouldn't overlook is "The World Above 50 MHz" column in January 2007 QST. This is the second of a two-parter that began in December's issue.

Last week's intense geomagnetic activity produced some nice auroral propagation on 6 meters. Jon Jones, N0JK, was operating portable atop a parking garage in Salina, Kansas, using a 2-element Yagi and running 30 W. On December 15 at 0015 UTC, he worked K9MU -- who was quite strong on SSB -- in Chippewa Falls, Wisconsin, more than 500 miles away. Later at 0225 UTC he heard KL7NO in Fairbanks working stations in nine-land. Fairbanks is about 2800 miles from Salina. By the way, I quickly calculated those distances using ZIP codes with a handy utility I ran across.

Jeff Hartley, N8II, of Shepherdstown, West Virginia, shared some interesting observations about the ARRL 10-Meter contest of two weeks ago and about auroral propagation from last week. Regarding the 10-meter contest, he reports working 1400 stations using "only" a 5-element monoband 10-meter Yagi at 98 feet -- three full wavelengths above ground. He continues:

"There was stable propagation (possibly F2) to NM and El Paso, TX, Sunday and a pipeline into AZ/NV. I probably worked a record number of NM, OK, KS, and IA stations during this year's event (latter 3 worked via plentiful Es). Worked EA8 (several and loud), 5H, 3X, S9SS, ZS on Sat AM and we had a very nice but only 2.25 hour long F2 West Coast opening starting around 1700z.

"Sunday it lasted longer, but CA was very weak and spotty and the Pacific NW was in and out, peaking at beginning and end of opening. A35RK called Sunday afternoon and biggest surprise was a Es to F2 link QSO with KH6NI at 0219z Sunday (ZL1CN was worked via same about 0120z). All states were worked except AK and ND and there certainly was prop to ND.

"The aurora starting around 0000z on the 15th was intense on 6M, but died out after 1 hour. It or auroral E probably returned later, but I was whipped. Signals peaked approximately NW and propagation favored that direction. Stations were heard from IA to VE2 and the beacons from MI and OH at one point were as loud as S9. There was not enough CW activity and a lot of guys just can't copy SSB sigs well with the phase distortion at 50 MHz."

Currently we've seen several days of zero sunspots. Expect few or no sunspots over the short term and planetary A indices December 22-27 of 15, 15, 10, 5, 5 and 15. The next predicted period of higher geomagnetic activity is around January 2, with a planetary A index of 25.

For More Information

For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service Propagation page and the article "The Sun, the Earth, the Ionosphere: What the Numbers Mean, and Propagation Predictions," by Carl Luetzelschwab, K9LA. An archive of past bulletins is on the ARRL Web site. The propagation charts that formerly appeared in QST now are available on the QST Propagation Charts page on the ARRL Web site.

Weekly Sunspot Numbers

Sunspot numbers for December 14 through 20 were 23, 19, 20, 11, 0, 0 and 0 with a mean of 10.4. 10.7 cm flux was 93.4, 87.1, 82.3, 81.3, 74.7, 72.9, and 71.5, with a mean of 80.5. Estimated planetary A indices were 63, 104, 11, 4, 8, 14 and 24 with a mean of 32.6. Estimated mid-latitude A indices were 30, 48, 10, 3, 7, 9 and 16, with a mean of 17.6.

Amateur solar observer Tad Cook, K7RA, Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears in The ARRL Letter. Readers may contact the author via e-mail.

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