Spaceweather.com reported that at 0209 UTC on July 14 a powerful M2 class solar flare and CME erupted, so geomagnetic predictions in this bulletin for the next few days may already be out of date.

Average daily sunspot numbers were 28.3 during this reporting week (July 6-12) up from 8 during the previous week. Average daily solar flux increased from 71.7 to 87.

Average planetary A index increased from 7.1 to 9.1, and average mid-latitude A index increased from 8.3 to 9.6.

Predicted solar flux is 92 on July 14-17, 90, 85 and 78 on July 18-20, 85 on July 21-28, 90 on July 29-30, 85 on July 31 through August 5, 87 on August 6-11, 85 on August 12-24, and 90 on August 25-26.

Predicted planetary A index is 12, 18 and 10 on July 14-16, then 15, 10, 8 and 5 on July 17-20, 11 on July 21-22, 5 on July 23 through August 4, then 25, 18, 12, 15 and 10 on August 5-9, then 5 on August 10-13, then 12, 10 and 5 on August 14-16, 11 on August 17-18, and 5 on August 19-26.

F.K. Janda, OK1HH of the Czech Propagation Interest Group sent this geomagnetic activity forecast for July 14 to August 10, 2017.

“Geomagnetic field will be:

Quiet on July 17, 25-26, August 1-2
Mostly quiet on July 16, 24, 27, 30-31, August 4, 8
Quiet to unsettled July 15, 18-20, 23, August 3
Quiet to active on July (13 -) 14, 21-22, 28-29, August 7
Active to disturbed on August 5-6

Amplifications of the solar wind from coronal holes are expected on July 13-16 (-17), 20-21, (23-24, 28-29,) August 6-8

Remark:
- Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.”

Currently, solar flux values are running higher than earlier predictions. This is because of the emergence of 2665, the largest sunspot group of 2017, now in a state of decay. Solar flux reached a recent high on July 10 of 95.1, but a week earlier predicted solar flux for that date was only 71.

Predicted solar flux for July 14-17 is 92.

Story from twin-cities (Minnesota) TV about the largest sunspot of 2017: http://kare11.tv/2tP87nJ


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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/.

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Sunspot numbers for July 6 through 12, 2017 were 16, 25, 24, 31, 32, 27, and 43, with a mean of 28.3. 10.7 cm flux was 75.9, 79.5, 86.6, 90.9, 95.1, 91.1, and 90.2, with a mean of 87. Estimated planetary A indices were 7, 5, 3, 28, 9, 8, and 4, with a mean of 9.1. Estimated mid-latitude A indices were 8, 5, 3, 26, 11, 9, and 5, with a mean of 9.6.