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The K7RA Solar Update


Excitement mounted a few days ago when new Solar Cycle 24 sunspot 1013 emerged, but two days later it was fading away, similar to other recent sunspot appearances. The sunspot number for February 24-26 was 12, 14 and 12. Today's number will likely be 0. Sunspot numbers for February 19-25 were 0, 0, 0, 0, 0, 12 and 14 with a mean of 3.7. The 10.7 cm flux was 68.9, 69.2, 70.6, 70.3, 70.8, 71 and 70.7 with a mean of 70.2. The estimated planetary A indices were 1, 3, 3, 3, 5, 6 and 3 with a mean of 3.4. The estimated mid-latitude A indices were 0, 3, 2, 3, 3, 6 and 2 with a mean of 2.7.

The vernal equinox is in a few weeks -- the first day of spring in the Northern Hemisphere -- March 20, 2009 at 1144 UTC. Areas north and south of the equator will be bathed in an equal amount of Sun, and this is always a good time for HF propagation.

Using one of the popular propagation programs to predict a path from California to Australia using an average sunspot number of 12, on 15 meters on January 20, there was a good chance of an opening from 2130-0100 UTC, with an excellent chance within that period, at 2330-0030 UTC. On March 20, using the same numbers, the chances of propagation look excellent from 2200-0230 UTC -- the band perhaps opening at 2130 UTC and shutting down at 0330 UTC. This gives us an illustration of propagation changing with the season.

Another example would be Dallas to Brazil. On January 20 on 20 meters, the band would probably be open from 1800-2300 UTC, with signals gradually increasing about 12 dB over that period. On March 20, a likely 20 meter opening would be from 1830-0230 UTC, with signals increasing 16 dB over that period and rising faster, as well.

Geomagnetic activity has been very quiet for a long time now, and this is expected to continue. NOAA and the US Air Force predict a planetary A index of 5 over the next two weeks, with minor exceptions. On March 3, the A index may rise to 8. Geophysical Institute Prague predicts quiet conditions February 28-March 2, quiet to unsettled March 3-4 then back to quiet on March 5. The predicted quiet conditions should be good for the CQ 160-Meter DX Contest this weekend.

Mike Schaffer, KA4JAW, lives in West Central Florida and enjoys observing sporadic-E propagation on broadcast television. His local channel 2 station, WEDU, ceased analog transmissions recently, eliminating co-channel interference with channel 3. On Sunday, February 22 just after 2300 UTC, Mike noticed a wrestling match on channel 3; shortly after, a logo appeared for TGV, a broadcaster in Guatemala City. That station is more than 1000 miles away.

Joaquin Montoya, EA2CCG, in Spain, reported good conditions over the past few days during the brief sunspot appearance. On February 25, 2100-2130 UTC, he worked a number of states in the western United States, including one in Montana while he was mobile on 20 meters. He could hear K5D, and earlier that day he worked K5D on 17 meters and 6V7P in Senegal, as well.

An Alaskan newspaper this week ran a story about subdued aurora due to low solar activity. Note their confusing comment about the Sun having an 11 year positive cycle following an 11 year negative cycle. Perhaps they refer to the switch in magnetic polarity in individual sunspots.

Amateur solar observer Tad Cook, K7RA, of 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. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



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