It's a new year, and now time to review 2007 sunspot cycle progression. In 2006 there was a consensus that solar minimum would occur in early 2007, but we actually may not be there still. The latest projection in the Weekly Preliminary Report and forecast (see http://www.swpc.noaa.gov/weekly/ and page 8 in the January 2 issue) shows the bottom of the cycle between December 2007 and April 2008. Note the two predictions for the next cycle, a high estimate and a low estimate, reflecting the split consensus for the Cycle 24 prediction.
Also note the monthly (even though the URL says weekly) forecast issued on January 2 at,
http://sec.noaa.gov/ftpdir/weekly/Predict.txt shows a cycle minimum for February 2008.
Exactly one year ago in Propagation Forecast Bulletin ARLP001 we wrote that 2007 would be "the year we'll likely see the end of sunspot Cycle 23, the beginning of Cycle 24, and the minima between cycles." Now a year later we might say the same about 2008.
The yearly average of the daily sunspot numbers for 1999-2007 were 136.3, 173, 170.3, 176.6, 109.2, 68.6, 48.9, 26.1 and 12.8. Average daily solar flux for the same years was 153.7, 179.6, 181.6, 179.5, 129.2, 106.6, 91.9, 79.9 and 73.1.
Compare 2006-2007 above with the last solar minimum, when in 1995-1997 the yearly averages of sunspot numbers were 28.7, 13.2 and 30.7.
In February 2007 we began calculating and tracking a 3-month moving average of daily sunspot numbers. This was done to try to spot trends. A three month period seemed like it might give us some smoothing of the often volatile daily numbers, but much shorter than the 12-month smoothed values.
Apr 06 38.5
May 06 39.7
Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3
Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
Jul 07 15.4
Aug 07 10.2
Sep 07 5.4
Oct 07 3
Nov 07 6.9
Why is November the last month on our list? Because it is the center month for the latest 3-month average, which is for October through December. If we were instead calculating a 12-month moving average, at the end of December the latest number would center on
June 2007.
Last week's bulletin reported 10-meter openings, and said that E-skip was unexpected at this time of year. Actually there is a small peak in sporadic-E propagation centered around Winter
Solstice, about 1/5 to 1/8 the intensity of the Summer sporadic-E season. The propagation reported by K7HP occurred just hours from the precise time of solstice.
One of several who spoke up concerning Winter E season in response to last week's bulletin was Bill Van Alstyne, W5WVO of Rio Rancho, New Mexico. Bill said that Winter E-skip is, "more likely to happen during the evening hours than during the morning, while Summer Es occurs during morning and evening about equally -- though that's just percentages and probability. We just had a nice morning Es opening a couple days ago on 6 meters."
Another Winter solstice 10-meter report came from Joaquin Montoya, EA2CCG, who reported working a number of Italian and French stations with his "fishing rod antenna." If you can read Spanish, or even want to try out one of those online language translators, check out his blog at, http://ea2ccg.blogspot.com/.
A December 30 10-meter E-skip report came from Oleh Kernytskyy, KD7WPJ of Saint George, Utah. In the morning he heard a strong beacon signal from K5AB, then he called CQ on CW with no response. He moved to phone and had many contacts, including the states of UT, NM, TX, OK, AR and FL.
See http://www.amfmdx.net/propagation/Es.html for an interesting treatment of E-layer propagation.
So what's up for the next week? Sunspot 978 reappeared, and the daily sunspot numbers for Tuesday, Wednesday and Thursday were 11, 13 and 13, while solar flux was 79.4, 79.6 and 79.3. The US Air Force and NOAA Space Weather Prediction Center forecast rising solar flux values of 80 for January 4-5, 85 for January 6-8, and 90 for January 9-11. This is a slight move downward and outward. As recently as two days ago, they were predicting flux of 95 for
January 7-9.
They also forecast planetary A index for January 4-10 of 10, 10, 5, 8, 8, 5 and 5. The next unsettled to active period is predicted for January 13-14 with a planetary A index of 15. After 2100z today look for an updated forecast of solar flux and A index at http://sec.noaa.gov/ftpdir/forecasts/45DF/010445DF.txt. Please note this is a hacked URL, that only works after 2100z Friday. It is updated daily, so for Saturday, January 5 after 2100z, the URL would end /010545DF.txt. This hack was explained back in October 2007, in ARLP044, found at http://www.arrl.org/w1aw/prop/2007-arlp044.html.
Geophysical Institute Prague predicts quiet to unsettled conditions January 4-5, unsettled January 6-7, quiet to unsettled again on January 8, and quiet conditions January 9-10.
The last few days have had very quiet with stable geomagnetic conditions. This should correlate with lower absorption of HF signals. You can see interesting very quiet numbers at,
http://www.sec.noaa.gov/ftpdir/indices/DGD.txt. Note the planetary A index for January 2-3 was 1 for both days, but all of the K index readings for those days were 0. Contrast that with the high latitude college (Fairbanks, Alaska) readings for January 2. There is just one K index reading of 1, but the A index reading for that day is 0.
KN4LF writes that he has decided to make his daily propagation forecasts free again, and you can see them at, http://www.kn4lf.com/kn4lf6h.htm. He also has a sign-up option there for email bulletins.
Last, today I am buying a used car from a private party found via an online ad. The seller turned out to be the grand-daughter of the original holder of VE7BR, A.J. Spilsbury, a remarkable Canadian radio pioneer who manufactured HF gear for marine and wilderness
communications in British Columbia. Spilsbury was also an accomplished painter, photographer, author of several books, and he founded a regional airline. He became a Silent Key in 2003 at age 97. I found information on him by googling his last name alone, or combined with other search terms such as "radio."
If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net.
For more information concerning radio propagation, see the ARRL Technical Information Service web page 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 December 27 through January 2 were 0, 0, 0, 0, 0, 11 and 13 with a mean of 3.4. 10.7 cm flux was 72.1, 71.8, 72.7, 75, 76.7, 79.4, and 79.6 with a mean of 75.3. Estimated planetary A indices were 4, 2, 2, 2, 2, 3 and 1 with a mean of 2.3. Estimated mid-latitude A indices were 4, 2, 2, 3, 2, 2 and 1, with a mean of 2.3.
