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ARRL Propagation Bulletin ARLP028 (2017)

SB PROP @ ARL $ARLP028
ARLP028 Propagation de K7RA

ZCZC AP28
QST de W1AW  
Propagation Forecast Bulletin 28  ARLP028
From Tad Cook, K7RA
Seattle, WA  July 14, 2017
To all radio amateurs 

SB PROP ARL ARLP028
ARLP028 Propagation de K7RA

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this bulletin for the next few days may already be out of date.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 to 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 to 17, 90, 85 and 78 on July
18 to 20, 85 on July 21 to 28, 90 on July 29 and 30, 85 on July 31
through August 5, 87 on August 6 to 11, 85 on August 12 to 24, and
90 on August 25 and 26.
 
Predicted planetary A index is 12, 18 and 10 on July 14 to 16, then
15, 10, 8 and 5 on July 17 to 20, 11 on July 21 and 22, 5 on July 23
through August 4, then 25, 18, 12, 15 and 10 on August 5 to 9, then
5 on August 10 to 13, then 12, 10 and 5 on August 14 to 16, 11 on
August 17 and 18, and 5 on August 19 to 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 and 26, August 1 and 2 
Mostly quiet on July 16, 24, 27, 30 and 31, August 4, 8 
Quiet to unsettled July 15, 18 to 20, 23, August 3 
Quiet to active on July (13 and) 14, 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 13 to 16 (and 17), 20 and 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."
 
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 to 17 is 92.
 
Story from twin-cities (Minnesota) TV about the largest sunspot of
2017:
 
http://kare11.tv/2tP87nJ
 
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 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.
NNNN
/EX