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ARRL Propagation Bulletin ARLP031 (2020)

SB PROP @ ARL $ARLP031
ARLP031 Propagation de K7RA

ZCZC AP31
QST de W1AW  
Propagation Forecast Bulletin 31  ARLP031
From Tad Cook, K7RA
Seattle, WA  July 31, 2020
To all radio amateurs 

SB PROP ARL ARLP031
ARLP031 Propagation de K7RA

Finally, sunspots have returned!  There are currently two sunspots
visible, both from new solar cycle 25.  The daily sunspot number was
11 on July 21 to 27, then rose to 22 on July 28 to 30.
 
Recently we have noticed an improvement in propagation due to
seasonal sporadic-E activity.
 
Average daily sunspot numbers rose from 3.1 to 14.1 this week, and
average daily solar flux changed from 69.1 to 71.1.
 
Total sunspot area covered 80 millionths of the solar disc on July
21, 120 millionths on July 22 to 26, and the coverage on the
following four days was 70, 50, 85 and 110.
 
Geomagnetic indicators were a bit more active, with average daily
planetary A index rising from 3.9 to 6.7, while average daily
mid-latitude indicators rose from 4.3 to 8.7.
 
Predicted solar flux is 72 on July 31 through August 2, 70 on August
3 to 7, 68 on August 8 to 22, 69 on August 23 to 28, and 68 on
August 29 through September 13.
 
Predicted planetary A index is 5 on July 31, then 8 and 10 on August
1 and 2, 5 on August 3 to 23, 8 on August 24 and 25, and 5 on August
26 through September 13.
 
Geomagnetic activity forecast for the period July 31 to August 26,
2020 from F. K. Janda, OK1HH.
 
"Geomagnetic field will be 
Quiet on: August 4 to 7, 15 to 19, 22 to 26 
Quiet to unsettled on: July 31, August 2 and 3, (8,) 9, 11, (12 to
14,) 20
Quiet to active on: (August 1, 10, 21) 
Unsettled to active on: not expected 
Active to disturbed: not expected 
 
Solar wind will intensify on: August 1 to 3 (-4, 11 to 15,) 20 and
21, (22 to 25)
 
- Parenthesis means lower probability of activity enhancement. 
- The predictability of changes remains lower, this time thanks to
new active regions on the Sun."
 
K7DWI has interesting details on his blog about using cheap SDR
dongles for studying VHF openings:
 
https://bit.ly/315dRdP
 
Thanks to Howard Lester, N7SO for this article on solar flares:
 
https://www.cfa.harvard.edu/news/2020-15
 
And thanks to regular contributor David Moore for this:
 
https://www.sciencedaily.com/releases/2020/07/200727145826.htm
 
The latest from Tamitha Skov, WX6SWW:
 
https://www.youtube.com/watch?v=vifDrXHwwsE
 
It looks like her entry on QRZ.com was recently updated and
expanded:
 
https://www.qrz.com/db/wx6sww
 
For more information concerning radio propagation, see
http://www.arrl.org/propagation and 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 July 23 through 29, 2020 were 11, 11, 11, 11,
11, 22, and 22, with a mean of 14.1.  10.7 cm flux was 70.3, 69.5,
70.4, 71.4, 71.4, 71.8, and 72.6, with a mean of 71.1.  Estimated
planetary A indices were 4, 11, 15, 3, 4, 5, and 5, with a mean of
6.7.  Middle latitude A index was 4, 13, 27, 3, 5, 5, and 4, with a
mean of 8.7.
NNNN
/EX