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ARRL Propagation Bulletin ARLP029 (2017)

SB PROP @ ARL $ARLP029
ARLP029 Propagation de K7RA

ZCZC AP29
QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 21, 2017
To all radio amateurs 

SB PROP ARL ARLP029
ARLP029 Propagation de K7RA

Average daily sunspot number this week declined just 1.7 to 26.6,
even though there were two days in the reporting week with no
sunspots, July 18 and 19.  The blank sun condition continued at
least one more day on Thursday, July 20 which lands it on the first
day of the next reporting week, July 20 to 26.
 
Average daily solar flux was 85.9, down 1.1 from the previous week.
 
Average planetary A index rose 3.9 points to 13, average
mid-latitude A index rose from 9.6 to 10.9.
 
A coronal mass ejection (CME) on July 16 struck at 0545 UTC driving
the planetary A index to 41, and 27 the following day.
 
Predicted solar flux is 70 on July 21 to 27, 75 on July 28, 90 on
July 29 through August 11, 85 on August 12 and 13, 80 on August 14,
74 on August 15 to 19, 75 on August 20 to 24, and 90 on August 25 to
September 3.
 
Predicted planetary A index is 8, 12 and 8 on July 21 to 23, 5 on
July 24 through August 4, then 25, 10 and 8 on August 5 to 7, 5 on
August 8 to 14, 8 on August 15 and 16, then 15 and 12 on August 17
and 18, 5 on August 19 to 31, and 25, 10 and 8 on September 1 to 3.
 
F. K. Janda, OK1HH of the Czech Propagation Interest Group sent us
this geomagnetic activity forecast for the period July 21 to August
8, 2017
 
"Geomagnetic field will be: 
Quiet on July 25 and 26, August 1 and 2 
Mostly quiet on July 24, 27, 30 and 31, August 4, 8 
Quiet to unsettled July 23, August 3 
Quiet to active on July 21 and 22, 28 and 29, August 7 
Active to disturbed on August 5 and 6 
 
Amplifications of the solar wind from coronal holes are expected on
July 21, (23 and 24, 28 and 29), August 6 to 8
 
Remark: 
- Parenthesis means lower probability of activity enhancement and/or
lower reliability of prediction."
 
David Moore sent a link to an excellent NY Times science article
titled "Unlocking Mysteries in the Sun's 11-Year Cycle."
 
http://nyti.ms/2tdddgv
 
Another interesting article:
 
https://cosmosmagazine.com/space/studying-the-solar-cycle
 
And the latest from Tamitha Skov:
 
http://bit.ly/2uOPeob
 
http://bit.ly/2vqusbs
 
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 July 13 through 19, 2017 were 55, 58, 34, 26,
13, 0, and 0, with a mean of 26.6. 10.7 cm flux was 92.3, 93.9,
91.6, 86.5, 85.6, 78.2, and 73.1, with a mean of 85.9.  Estimated
planetary A indices were 4, 4, 4, 41, 27, 7, and 4, with a mean of
13. Estimated mid-latitude A indices were 5, 3, 4, 29, 23, 7, and
5, with a mean of 10.9.
NNNN
/EX