Average daily sunspot numbers dropped from 19.3 last week to 10.7 in the current reporting week, July 28 through August 3. Average daily solar flux declined from 82.5 to 72.1.

Geomagnetic indices were more active this week, with average daily planetary A index increasing from 8.7 to 13, and mid-latitude A index rising from 8.9 to 11.9.

Sunspot numbers were low all week, and on Wednesday August 3 the sunspot number dropped to zero, as in no sunspots. And there were still no sunspots the next day, August 4.

Predicted solar flux is 80 on August 5-7, then 85, 90 and 95 on August 8-10, 100 on August 11-12, 95 on August 13-15, 90 on August 16-17, then 85 and 80 on August 18-19, 75 on August 20-22, 70 on August 23-27, 72 on August 28-30, 75 on August 31, 85 on September 1, 90 on September 2-3, then 95 on September 4-11 and 90 on September 12-13.

Predicted planetary A index is 15 on August 5-6, then 10, 20, 8, 12, 10 and 8 on August 7-12, 5 on August 13-14, 12 on August 15-16, 5 on August 17, 8 on August 18-19, 5 on August 20-23, 15 on August 24-25, 5 on August 26-27, 8 on August 28, 20 on August 29-30, 15 on August 31, 12 on September 1, 10 on September 2-3, then 8 and 5 on September 4-5, 12 on September 6-7, 8 on September 8, 5 on September 9-10 and 12 on September 11-12.


Geomagnetic activity forecast for the period August 5-August 31, 2016 from OK1HH of the Czech Propagation Interest Group.

Geomagnetic field will be:
Quiet on August 13-14, 23, 27-28
Mostly quiet on August 22
Quiet to unsettled on August 5, 9, 11-12, 15, 18, 24, 31
Quiet to active on August 6, 10, 20, 25-26, 30
Active to disturbed on August 7-8, (16-17, 21,) 29

Increasing solar wind from coronal holes is expected on August 5-8 (- 9), 14, 22-23, 29-30

Parenthesis means lower probability of activity enhancement.


The Times of India has an article on solar flares at http://bit.ly/2aCj0Sn

Howard Schler, K2EQ of Ovid, New York wrote:

“I wanted to point out one oddity of propagation that has been occurring on a daily basis for many weeks though now a bit less.

“On 20 meters, each day between midnight local time 0500Z to about 0630 or 0700, PSK is almost completely dead, less than a handful of stations and most very weak and broken up.

“However, the surprising exception is that in the midst of that I have been able to work VKs, ZLs and other South Pacific stations from my home in New York with good to excellent signals, sometimes 10,000 miles away and the only signal on the PSK spectrum.  We both marvel at the propagation and how odd it is yet how strong our signals are.  I do not understand propagation beyond a very fundamental level.  Nonetheless, there it is and I’m up way past my bedtime almost every night calling into a blank noisy band, with surprising results.”

Often when a band seems dead, you can call CQ and find out there is good propagation, but you haven't heard anyone calling, so it seems like there is no propagation.

Around that time from your place to ZL on 20 meters should be an excellent path, according to some path projections I ran with W6ELprop.

Looks like the path opens up about 0230 UTC, and an hour later is about 5 dB better. Signals slowly climb until 0530, then level off, and then start to fade after 0700. But on some days there could be strong signals until 1130 UTC.

Time to look at our 3 month moving average of sunspot numbers, now that July is over. The moving average ending in January through July was 55.4, 53.5, 49, 45.3, 43.1, 35.4 and 33. Looks like a steady decline in solar activity, although I am surprised to see so many zero sunspot days at this point in the declining cycle.


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 July 28 through August 3 were 13, 13, 13, 12, 13, 11, and 0, with a mean of 10.7. 10.7 cm flux was 70.3, 70.5, 71, 71.5, 71.9, 74.9, and 74.8, with a mean of 72.1. Estimated planetary A indices were 15, 14, 6, 3, 3, 17, and 33, with a mean of 13. Estimated mid-latitude A indices were 13, 16, 7, 2, 4, 17, and 24 with a mean of 11.9.