Saturday, January 12, 2008
ARLP002 Propagation de K7RA
We just saw eight days of sunspots, but now the solar disk is spot-free. The big story this week is the sighting of the first spot of sunspot Cycle 24. The sunspot has now faded away, but a new spot is emerging near the solar equator, and it has the same polarity as the Cycle 24 spot last week. This is odd, because the spots from the new cycle should emerge at high latitudes, like last week's did.
News reports this week said Cycle 24 has begun, but actually Cycle 23 hasn't ended yet. Cycle 24 spots should gradually increase in number, while Cycle 23 spots fade away. Some time around solar minimum we should see the count of Cycle 24 spots equal, and then outnumber Cycle 23 spots. I believe that is really the start of the next cycle, when we begin to see more Cycle 24 spots emerging than Cycle 23 spots.
Average sunspot numbers this week were nearly 10 points above last week's average, at 13.3. Unsettled geomagnetic conditions were observed on January 5-8. Last week the prediction for solar flux for earlier this week looked optimistic. Go to
http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html and click on the December 30 forecast.
Note the prediction for solar flux of 85 for January 4-11. Then click back, and look at December 31. On that day it predicted a solar flux of 90 for January 5-7. The January 1 prediction is even higher at solar flux 95 for January 7-8. The next day, January 2 shows flux at 95 for January 7-9. January 3 is less optimistic, with flux peaking at 90 for January 9-11, although some of the dates are mislabeled. January 4 shows flux peaking for one day, January 6, at 85. None of those predictions came to pass, and solar flux was actually below 80 the entire week.
NOAA and the Air Force predict planetary A index values for January 11-17 at 5, 5, 15, 15, 10, 12 and 10. If you want an updated forecast after 2100z today, use the URL above and go to the January 10 forecast (if January 11 isn't shown yet). Then change a series of characters in the URL from 011045DF.txt to 011145DF.txt, and hit the Enter key. You should see an updated forecast for solar flux and planetary A index before the link appears on the main page.
Australia's IPS Radio and Space Services released a warning for a geomagnetic disturbance caused by a high speed solar wind stream from a coronal hole for January 13-14. This is reflected in the forecast in the previous paragraph, calling for a planetary A index of 15 for both those days. Geophysical Institute Prague predicts quiet conditions January 11-12, quiet to unsettled January 13, active conditions January 14, unsettled to active January 15, and unsettled conditions January 16-17.
For HF radio propagation, we would generally like to see sunspot numbers high, and A index geomagnetic readings low.
Last week Randy Crews, W7TJ reported excellent short path propagation to Europe on 160 and 80 meters on the night of January 3. Bob Culbertson, WA3YGQ of Cranberry, Pennsylvania said 80 meter propagation to Europe was the best he ever heard, with signals 20 db over S9. At 1230z he could hear Japan quiet strongly.
But Ken Gordon, W7EKB of Moscow, Idaho runs regional message traffic on 80 meters, and reported that the same night he experienced terrible conditions on 80 meters. Ken was net control for the RN7 net on 3560 kHz at 0330z and again at 0530z, and he could hardly hear anyone. But stations sitting at 800 miles and beyond were booming in. Lately he's had an experience earlier in the evening on a net at 0030z on 3910 kHz in which signals from Montana are readable, but 10-15 minutes later they fade away and signals from the West Coast come in quite strong. The skip seems to be going long.
Jon Jones, N0JK of Wichita, Kansas sent comments regarding 10 meter Winter E-skip. He noted a number of strong E-skip openings on Saturday night in December's 10 Meter Contest. He made many contacts running QRP into a 6-meter loop.
Jon said he agrees with Bill Van Alstyne, W5WVO of Rio Rancho, New Mexico, that "most of the winter E-skip occurs during late afternoon and early evening hours. Summer E-skip tends to occur more frequently in the mid-morning hours, with a secondary peak in the evening." He wonders why Winter and off-season E-skip is more likely in the evening, but Summer E-skip seems more frequent in the morning?
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For more information concerning radio propagation, see the ARRL Technical Information Service at, http://www.arrl.org/tis/info/propagation.html. For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html. An archive of past propagation bulletins is at, http://www.arrl.org/w1aw/prop/. Monthly propagation charts between four USA regions and twelve overseas locations are at http://www.arrl.org/qst/propcharts/.
Sunspot numbers for January 3 through 9 were 13, 26, 12, 12, 14, 16 and 0 with a mean of 13.3. 10.7 cm flux was 79.3, 79, 79.7, 79.2, 77.7, 75.5, and 76.5 with a mean of 78.1. Estimated planetary A indices were 1, 2, 18, 13, 12, 13 and 6 with a mean of 9.3. Estimated mid-latitude A indices were 1, 2, 13, 12, 10, 11 and 6, with a mean of 7.9.