All solar indicators rose over the past week (August 17-23), with average daily sunspot number increasing from 15.3 to 39.9, and average daily solar flux from 72 to 84.6, compared to the previous seven days.

Predicted solar flux is 79 on August 25, 80 on August 26, 78 on August 27-30, 75 on August 31, 78 on September 1-2, 75 on September 3-7, 80 on September 8, 85 on September 9-14, 88 on September 15-16, 90 on September 17-22, 85 and 80 on September 23-24, 78 on September 25-29, 75 on September 30 through October 4, 80 on October 5, and 85 on October 6-8.

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

And now from our correspondents in Eastern Europe:

“Solar activity forecast for the period August 25-August 31, 2017

Activity level: mostly low
X-ray background flux (1.0-8.0 A): in the range A8.0-B4.5
Radio flux (10.7 cm): a fluctuation in the range 75-95 f.u.
Events: class C (0-5/day), class M (0-4/period), class X (0/period), proton (0/period)
Relative sunspot number (Ri): in the range 11-80

Martina Exnerova
RWC Prague, Astronomical Institute, Solar Dept., Ondrejov, Czech Republic

Geomagnetic activity forecast for the period August 24-August 31, 2017

Quiet: Aug 26-29
Unsettled: Aug 24-25, 30-31
Active:    Aug possible Aug 31
Minor storm: 0
Major storm: 0
Severe storm: 0

Geomagnetic activity summary:
Currently, an active episode has been recorded. At the Budkov observatory, the local K-index did not exceed level 4.

Thursday, August 24, we expect at most unsettled conditions. Next day, Friday, August 25, we expect geomagnetic activity decrease to quiet to unsettled level.
Quiet to unsettled conditions are predicted for the rest of forecast period. At the end of August, active episode is possible about August 31.

Tomas Bayer
RWC Prague
Institute of Geophysics of the ASCR, Prague
Department of Geomagnetism
Budkov observatory (BDV)”


Did you witness the eclipse on Monday? I found a group of my neighbors gathered on the street corner after 1700 UTC, and they had one of those taped-together box arrangements for projecting the image. We were in Seattle, north of the band of darkness that spread over northern Oregon. Someone drove by with a box of those special safe eclipse glasses, and they worked very well.

Reports from friends who travelled to Madras, in Eastern Oregon’s Jefferson County reported that in the middle of the totality band they saw the sky go totally dark, and stars illuminated the sky.


Scott Craig, WA4TTK of Nashville, Tennessee sent this, along with a link to eclipse photos he took: “Thought you might like these. They are photos of Monday's eclipse taken here in Nashville. I took them and keep looking at them because I find them fascinating.” http://sc-photo-tn.com/?page_id=2389


For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of 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 17-23, 2017 were 30, 41, 33, 44, 43, 48, and 40, with a mean of 39.9. 10.7 cm flux was 76.7, 80, 86.8, 86, 87.1, 90.2, and 85.1, with a mean of 84.6. Estimated planetary A indices were 29, 21, 31, 22, 11, 23, and 25, with a mean of 23.1. Estimated mid-latitude A indices were 20, 20, 23, 21, 13, 16, and 17, with a mean of 18.6.