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12/5/17

The K7RA Solar Update


The K7RA Solar Update

05/12/2017
Average daily sunspot numbers this week (May 4-10) were 17.1, down from 25.1 last week. Average daily solar flux declined from 76.9 to 71.5.

There were three consecutive days with zero sunspots this week, May 9-11. Spaceweather.com noted that Thursday was the thirty-third day with zero sunspots in 2017, and through all of 2016 there were 32 days with no sunspots. Being early May, this indicates an acceleration of the decline of the current solar cycle.

Predicted solar flux is 71 on May 12-13, 70 on May 14-17, 80 on May 18-23, 77 on May 24-27, 75 on May 28 through June 1, 73 on June 2, 72 on June 3-4, 70 on June 5-8, 72 on June 9-10, 75 on June 11, and 80 on June 12-19.

Predicted planetary A index is 6 on May 12, 5 on May 13-16, 15 on May 17-18, then 8, 15, 30, 20, 10 and 8 on May 19-24, 5 on May 25 through June 3, 8 on June 4, 5 on June 5-7, then 8, 5, 5 and 8 on June 8-11, then 15, 30, 15 and 8 on June 12-15.

Both above Ap and 10.7 cm SF forecasts are from Wednesday May 10. As of 1430 UTC Friday the Thursday May 11 forecast (normally out after 2100 UTC daily) was still unavailable.

You can check ftp://ftp.swpc.noaa.gov/pub/forecasts/45DF/ for daily updates of predicted Ap (planetary A index) and solar flux predictions.

OK1HH gives us his geomagnetic activity forecast for May 12-June 7, 2017.

Geomagnetic field will be:
Quiet on May 14-15, June 1,
Mostly quiet on May 13, June 4
Quiet to unsettled May 12, 23-30, June 3, 5-7
Quiet to active on May 16, 20, 21-22, June 2
Active to disturbed on May (17-19, 31)

Amplifications of the solar wind from coronal holes are expected May 16-19 (and maybe about May 29-30 and June 3, 6, 7-8)

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

F.K. Janda, OK1HH
Czech Propagation Interested Group
OK1HH compiling weekly forecasts since 1978.


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 May 4 through May 10, 2017 were 29, 31, 26, 23, 11, 0, and 0, with a mean of 17.1. 10.7 cm flux was 74.2, 73.5, 72.8, 71.7, 70.5, 68.9, and 68.6, with a mean of 71.5. Estimated planetary A indices were 7, 6, 5, 8, 6, 6, and 6, with a mean of 6.3. Estimated mid-latitude A indices were 6, 5, 5, 7, 7, 5, and 6, with a mean of 5.9.

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