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The K7RA Solar Update


Solar indices and outlook are stronger this week. Average daily sunspot numbers rose 19.7 points to 114.6, while average daily solar flux increased 25.7 points to 138.8. Average daily estimated planetary A index dropped from 7.4 to 4.3. This compares the August 14-20 period against the previous seven days.

The day with the greatest geomagnetic activity was Tuesday, August 19 when the planetary A index was 17. This was caused by a weak CME, but according to the inner magnetic structure “contained a region of south pointing magnetism that partially cancelled Earth’s north pointing magnetic field.” This opened a crack in the magnetosphere, and solar wind poured through, triggering unexpectedly brilliant aurora.

The outlook for solar activity has improved. A week ago the average predicted solar flux for the next ten days, August 22-31, was 121. Now based on the Thursday, August 21 prediction the average solar flux for the same period has risen to 149.5, a robust increase of 28.5 points.

Predicted solar flux is 140 on August 22-26, 150 on August 27, 160 on August 28-30, and 165 on August 31. Flux values then drop to 125, 130, 125, 120, 115 and 110 on September 1-6, 105 on September 7-9, 100 on September 10 and 110 on September 11-12. It meanders a bit, and then rises to 140 on September 24 before declining again.

Predicted planetary A index is 8 on August 22, 5 on August 23-28, 8 on August 29, then 5, 12, 10 and 8 on August 30 through September 2, 5 on September 3-5, 8 on September 6-7, 10 on September 8, 5 on September 9-14, 12 and 14 on September 15-16, then 8 on September 17-18, and 5 on September 19-23.

F.K. Janda, OK1HH, predicts the geomagnetic field will be quiet to unsettled August 22, active to disturbed August 23, quiet to unsettled August 24, mostly quiet August 25, quiet to active August 26-29, active to disturbed August 30, quiet to active August 31, mostly quiet September 1-2, quiet to unsettled September 3, quiet September 4-5, quiet to unsettled September 6, quiet September 7, mostly quiet September 8 and quiet to unsettled September 9.

Jon Jones, N0JK, reports a late season E-skip opening on August 16 around 0015 UTC. AA6YQ (FN42) was very loud on 6 meters across the south and Midwest.

Several stations in Washington State heard the VE8WD six meter beacon on 50.02 MHz from Yellowknife, Northwest Territories at 0220-0249 UTC on August 20. The distance was about 1100 miles.

Check out the DX maps at . You can look at real time contacts on 10, 6 or 2 meters, giving a picture of propagation around the world. Right now at 1300 UTC the sun is rising over the West Coast of North America, and I am looking at a large number of 6 meter contacts all over Europe. I switched to 10 meters, and I can see contacts between Europe and Ethiopia, Thailand, Algeria and Saudi Arabia.

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the numbers used in this bulletin, see An archive of past propagation bulletins is at More good information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for August 14 through 20 were 108, 119, 99, 121, 92, 84, and 89, with a mean of 114.6. 10.7 cm flux was 102.7, 113.1, 112, 115.1, 110.6, 111, and 118, with a mean of 138.8. Estimated planetary A indices were 4, 5, 3, 7, 5, 17, and 6, with a mean of 4.3. Estimated mid-latitude A indices were 5, 6, 4, 9, 5, 14, and 7, with a mean of 3.7.




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