ARRL Propagation Bulletin, 15 October 2018

Accessed on 16 October 2018, 0050 UTC, Post #728.


Author:  Tad Cook (K7RA).

Please click link or scroll down to read the complete report.

Comment:  Here is the latest ARRL Propagation Forecast from Tad Cook (K7RA) and his staff of volunteer contributors. Views expressed in this bulletin are those of Mr. Cook and his correspondents.

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 12, 2018
To all radio amateurs 

ARLP041 Propagation de K7RA

Last week this bulletin reported a return of sunspot activity on
September 29 after a 16 day absence from September 13-28, but the
new activity only lasted 6 days. As of Thursday night (October 11)
we are now at 7 days with no sunspots visible.

Average daily sunspot number declined from 9.6 to 1.6, while average
daily solar flux rose slightly from 68.4 to 68.9.

Average planetary A index increased from 7.7 to 14.1, while
mid-latitude A index rose from 6.1 to 10.3.

Predicted solar flux is 71 on October 12, 70 on October 13-18, 69 on
October 19 through November 25.

Predicted planetary A index is 8, 5, 12 and 8 on October 12-15, 5 on
October 16-17, 12 on October 18-19, then 14, 8 and 12 on October
20-22, 8 on October 23-25, 10 on October 26, 5 on October 27 through
November 2, then 22 and 35 on November 3-4, 15 on November 5-6, then
10, 8, 5, 10 and 8 on November 7-11, 5 on November 12-13, then 10,
25, 14, 8 and 12 on November 14-18, 8 on November 19-21, 10 on
November 22 and 5 on November 23-25.

Conditions should continue at marginal levels because of weak solar

I keep checking the weekly Preliminary Report and Forecast from SWPC
(see ) because
once a month they update solar cycle predictions for smoothed
sunspot number and smoothed 10.7 cm solar flux.

For the past several years (at least back to early 2015) the
projection ended in December 2019. It is widely believed that this
cycle (Solar Cycle 24) should reach solar minimum in 2020, so I keep
checking for projections that go past 2019, but so far nothing new
is posted.

You can see the latest projection in a recent bulletin on pages
10-11 at .

It shows the predicted smoothed sunspot number for October 2018 at

Because the smoothed sunspot number is averaged over a year, this
means that about half of the current average is made up of real
sunspot numbers averaged over the past 6 months and the other part
of the average is made up of predicted sunspot numbers over the next
6 months. So as you look at the averages, for every month you look
back, you see the results of more and more real sunspot numbers.

Note that in July 2018 the projected smoothed sunspot number is only
1. This may change as time goes on and more of actual sunspot
numbers are figured into the average.

More detail on smoothed sunspot numbers:

Geomagnetic activity forecast for the period October 12 to November
07, 2018 from F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on October 13, 16, 29-31, on November 1
Quiet to unsettled on October 14-15, 17, 27, 31
Quiet to active on October 12, 20, 22-26, on November 2, 7
Unsettled to active on October 18, 21, 28, on November 5-6
Active to disturbed on October 19, on November 3-4

"Solar wind will intensify on October 12-13, (14,) 17-20, (27-28,) on
November 2-5

"Remark: - Parenthesis means lower probability of activity

If you would like to make a comment or have a tip for our readers,
email the author at, .

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at, For an explanation of
numbers used in this bulletin, see

An archive of past propagation bulletins is at More good
information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for October 4 through 10, 2018 were 11, 0, 0, 0, 0,
0, and 0, with a mean of 1.6. 10.7 cm flux was 67.2, 68.7, 68.6,
69.5, 68.8, 69.5, and 69.8, with a mean of 68.9. Estimated planetary
A indices were 4, 9, 6, 24, 21, 17, and 18, with a mean of 14.1.
Estimated mid-latitude A indices were 4, 8, 5, 13, 16, 14, and 12,
with a mean of 10.3.
For the latest Amateur/Ham Radio news and information, please check
the blog sidebars and links.  These news feeds are updated daily and
weekly.  Thanks for joining us today.
Aloha es 73 de 
Russell Roberts (KH6JRM).
Public Information Coordinator
Hawaii County, ARRL Pacific Section