Compared to the previous seven days, solar activity dropped over the past week December 4-10 with average daily sunspot numbers down 63.6 points to 88.4, and average daily solar flux off 32.5 points to 139.6. But both numbers were higher on December 11, a good sign.

The latest forecast has solar flux at 155, 160, and 165 on December 12-14, 170 on December 15-17, 165 on December 18, 170 on December 19-20, 165 and 150 on December 21-22, 155 on December 23-27, 150 on December 28-29, 145 and 140 on December 30-31, 135 on January 1-4, then 140, 145, 150, 155 and 160 on January 5-9 and 165 on January 10-12. It then reaches a peak of 175 on January 14-15.

Predicted planetary A index is 5 on December 12, 18 on December 13, 15 on December 14-15, 12 on December 16-18, 10 on December 19-20, 5 on December 21-27, 8 on December 28-30, 10 on December 31 and January 1, then 12, 25, 15 and 10 on January 2-5, 8 on January 6-7, 10 on January 8-9, 8 on January 10-12, 10 and 12 on January 13-14, and 10 on January 15-16.

Let’s see what OK1MGW has for us in his prediction for geomagnetic conditions.

OK1MGW sees quiet to active conditions December 12-13, quiet to unsettled December 14-15, quiet to active December 16-17, quiet to unsettled December 18-20, mostly quiet December 21, quiet December 22, mostly quiet December 23-24, quiet December 25-26, quiet to unsettled December 27-28, mostly quiet December 29-31, quiet to unsettled January 1-2, active to disturbed January 3, quiet to active January 4-5, and quiet to unsettled January 6-7.

He believes there will be an increase in solar wind on December 13, 16-18 and January 2-5.

Don’t forget this weekend is the annual ARRL 10 Meter Contest (see http://www.arrl.org/10-meter for rules and general information). This is a really fun event, and due to the nature of ten meters, it always holds many surprises. The Geminids meteor shower peaks this weekend, and it is likely that ionized meteor trails could enhance propagation at the high end of the HF spectrum.

It is also really easy to get a 10 meter station on the air with minimal effort. A half-wave dipole is only about 16.5 feet long for this band, and you can hang it off just about anything to get it some minimal distance in the air. Also, Technician class hams can participate in this one using SSB on 28.3-28.5 MHz and CW on 28.0-28.3 MHz. There is also an easy 10 meter vertical described at the ARRL URL above for the 10 meter contest.

I was predicting conditions should be slightly better than they were during the 2013 contest, with somewhat higher solar activity about the same geomagnetic instability. But now the geomagnetic conditions look a little worse.

The December 10 planetary A index for December 12-14 was 5, 12 and 12. The December 11 forecast shows 5, 18 and 15 for those same days, or a little bit worse. These daily forecasts are at ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/. Check it again today after 2100 UTC. Maybe it will be better.

In 2013 the solar flux on Friday through Sunday on the contest weekend was 141, 163 and 158, for an average of 154. This weekend the predicted Friday through Sunday solar flux is 155, 160 and 165, which averages out to 160. Last year the planetary A index over those same three days was 3, 16 and 7, average value 8.7. This year’s forecast is 5, 18 and 15, with an average of 12.7. We’ll see what happens.

Check 2013 bulletins at http://www.arrl.org/w1aw-bulletins-archive/ARLP051/2013 and http://www.arrl.org/w1aw-bulletins-archive/ARLP052/2013 to see a comparison with propagation from previous years and what the numbers were on the contest weekend.

NOAA Space Weather Prediction Center has transitioned to their new servers, so you will want to check ftp://ftp.swpc.noaa.gov/pub/indices/DSD.txt and ftp://ftp.swpc.noaa.gov/pub/indices/DGD.txt for solar flux, sunspot and geomagnetic indices, and ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/ for the daily 45-day forecast. Of course Canada still serves up their same three times per day solar flux numbers from their observatory at both http://www.spaceweather.ca/solarflux/sx-5-flux-eng.php and ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_values/fluxtable.txt , take your pick -- HTML or plain text.

Dick Bingham, W7WKR, sent along some interesting historical material on early Amateur Radio, assembled by W2PA. Check it out at http://w2pa.net/HRH/ .


For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

Monthly propagation charts between four USA regions and twelve overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending e-mail distribution of ARRL bulletins are at http://arrl.org/bulletins.

Sunspot numbers for December 4 through 10 were 137, 97, 73, 58, 77, 80, and 97, with a mean of 88.4. 10.7 cm flux was 157.6, 136.8, 128.7, 131.8, 132.6, 139.7, and 149.8, with a mean of 139.6. Estimated planetary A indices were 11, 11, 13, 28, 17, 15, and 9, with a mean of 14.9. Estimated mid-latitude A indices were 8, 8, 10, 19, 11, 12, and 6, with a mean of 10.6.