Again this week, solar activity was unchanged, with average daily sunspot numbers slipping from 85.4 to 85, and average daily solar flux increasing 4.4 points to 111.7. Geomagnetic conditions were stable.

The latest solar flux prediction from USAF/NOAA has flux values of 125 on August 16, 130 on August 17-18, 120 on August 19-20, 110 on August 21-23, 105 on August 24, 110 on August 25-26, 115 on August 27-29, 110 on August 30, 105 on August 31 through September 6, then 110 and 115 on September 7-8 and 120 on September 9-11.

Predicted planetary A index is 12 and 8 on August 16-17, 5 on August 18-19, then 12 and 15 on August 20-21, 8 on August 22-23, 5 on August 24-30, then 12, 15, and 10 on August 31 through September 2, and 5 on September 3-7.

OK1HH issues his own weekly geomagnetic activity forecast, and he sees mostly quiet geomagnetic conditions August 16-17, quiet to active August 18, quiet on August 19, mostly quiet August 20, quiet August 21, active to disturbed August 22, quiet to unsettled August 23, quiet to active August 24, quiet to unsettled August 25-28, quiet August 29-30, active to disturbed September 1, quiet to unsettled September 2, quiet on September 3-5, mostly quiet September 6-8, active to disturbed September 9, quiet to active September 10, and active to disturbed September 11. OK1HH says “a positive storm phase” is expected August 22, and a growing solar wind may cause remarkable changes in the magnetosphere and ionosphere on August 16, and 21-22, and September 1-2, 6-7, and 11.

At 0318 UTC on August 16, the Australian Space Forecast Centre issued a geomagnetic warning, saying a high speed wind stream is spewing from a coronal hole. Unsettled to active geomagnetic levels are expected today, August 16, and minor storm levels are possible.

Scientific American has a 60 second podcast explaining why the changing magnetic polarity of the sun is nothing to worry about. Listen at http://www.scientificamerican.com/podcast/episode.cfm?id=solar-magnetic-field-flip-poses-no-13-08-15.

We get our solar flux data directly from the observatory in Penticton, British Columbia where they measure and report the numbers. It has been available at ftp://ftp.geolab.nrcan.gc.ca/data/solar_flux/daily_flux_values/fluxtable.txt but this week that server seemed unreachable. I poked around for quite some time and finally found the same data in html rather than plain text format at http://www.spaceweather.ca/data-donnee/sol_flux/sx-5-flux-eng.php.

Al Kaiser, N1API of Meriden, Connecticut asked, “If you have two flares at the same time from two different sunspot areas on the sun, do they add up to give a bigger class of flare, or just end up a one longer event?”

They are counted and rated separately. And if the flares are on different areas of the sun, they are probably pointing in different directions, so one or both might not affect earth.

Randy Crews, W7TJ of Spokane, Washington has long been fascinated by the idea that the current solar cycle 24 may turn out to have two peaks, like the last few cycles. He writes, “There have been several predictions that cycle 24 might have a second peak. Well maybe - maybe not. Cycle 21 had a definite single peak: November of 1979. Cycle 22 had two peaks: September of 1989 and January of 1991. Cycle 23 also had two peaks: April/July of 2000 and December of 2001. K9LA presented some interesting analysis regarding the declining magnetic strength of sunspots since 1995 and especially cycle 24.” See http://myplace.frontier.com/~k9la/Looking_Ahead_To_Solar_Cycle_25.pdf

Randy continues, “Anyone who brings up a NASA photo of sunspots during Cycle 21-23 will see many large magnetically complex sunspots vs. Cycle 24’s ‘freckles’ of small magnetically simple spots. So we MAY see a second peak IF the magnetic strength of the sunspots holds, or better yet increases. If not, a second peak is doubtful, and chances are the peak of activity has passed (as defined by the average monthly solar flux and average monthly sunspot count). The Sun is always full of surprises. During the CQWW Contest of October 2003 the solar flux punched up to 290!”

Ah, Randy, wouldn’t that be nice to see again! In fact, your current author’s stewardship of this bulletin began in 1991, not because of any particular expertise regarding astrophysics, but due to a similar sudden burst of solar activity, which happened to coincide with the former (and only other) author of this bulletin becoming too ill to write (see http://oldqslcards.com/W1HDQ.pdf). The event was Thursday, January 31, 1991 when the solar flux reached 357. Someone needed to write about this. I had no idea when I alerted folks in Newington that it would be me.


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 email distribution of ARRL bulletins are at http://arrl.org/bulletins.

Sunspot numbers for August 8 through 14 were 90, 51, 76, 90, 85, 98, and 105, with a mean of 85. 10.7 cm flux was 104.4, 103.6, 102.5, 110.4, 114.1, 122, and 125.2, with a mean of 111.7. Estimated planetary A indices were 5, 9, 6, 6, 6, 9, and 10, with a mean of 7.3. Estimated mid-latitude A indices were 4, 11, 7, 7, 6, 9, and 9, with a mean of 7.6.