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ARRL Propagation Bulletin ARLP034 (2020)

ARLP034 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 34  ARLP034
From Tad Cook, K7RA
Seattle, WA  August 21, 2020
To all radio amateurs 

ARLP034 Propagation de K7RA

Sunspots disappeared during four days over the past week, but then
came back.  Average daily sunspot number declined from 14.3 to 5.4,
while average daily solar flux went from 73.8 to 71.
Geomagnetic indicators remain quiet.  Average daily planetary A
index increased from 3.7 to 4.4.
Predicted solar flux is 70 on August 21 and 22, 69 on August 23 to
28, 72 on August 29, 73 on August 30 to September 5, 72 on September
6 to 9, 71 on September 10 and 11, 70 on September 12 to 19, 71 on
September 20 o 23, 72 on September 24 and 25, 73 on September 26 to
October 2, and 72 on October 3 and 4.
Predicted planetary A index is 5 on August 21 and 22, 6 on August 23
to 25, 5 on August 26 to 28, 8, 16 and 8 on August 29 to 31, then 5
on September 1 to 14, 10 on September 15 and 16, 5 on September 17
to 24, then 8, 16 and 8 on September 25 to 27, and 5 on September 28
to October 4.
Geomagnetic activity forecast for the period August 21 to September
16, 2020 from F. K. Janda, OK1HH.
"Geomagnetic field will be 
Quiet on: September 5 to 7 
Quiet to unsettled on: August 22, (23,) 24 and 25, (26 to 28,)
September 2 to 4, 8 and 9
Quiet to active on: (August 21, 29 to 31, September 1, 16) 
Unsettled to active: not expected  
Active to disturbed: not expected  
Solar wind will intensify on: August (21 to 23,) 24 and 25, 29,
September 1 and 2, (4 to 6,) 8, 15 and 16
- Parenthesis means lower probability of activity enhancement."  
- Next Geomagnetic activity forecast will be issued on 3rd
September, so it must be time for OK1HH to take his annual vacation.

Thanks to Max White for this link to an article about a dent in
Earth's magnetic field and the South Atlantic Anomaly:
The latest report from Tamitha Skov, WX6SWW, the Space Weather
The CME she spoke of turned out not to be geo-effective, so we
missed a disturbance.
From reader David Moore, info on the NASA THEMIS Mission:
"A special type of aurora, draped east-west across the night sky
like a glowing pearl necklace, is helping scientists better
understand the science of auroras and their powerful drivers out in
George Hall, N2CG wrote:
"Reading The K7RA Solar Update 08/14/2020 issue of your personal
experience of solar Cycle 19 when you were a young boy with your dad
listening to the low band VHF FM 2-Way radio in your dad's company
car in California and suddenly hearing stations in Texas and other
Midwestern states brought back fond memories of a similar nature I
experienced in Solar Cycle 20.
I was a Radioman on active duty in the USCG stationed at Coast Guard
Radio Station NIK/NJN located on the U.S. Naval Air Station
Argentia, Newfoundland CANADA.  One day the Crash Crew (a fire
department specifically devoted to incidents on the airport with
specially equipped fire trucks that could literally drive right up
on top of a fire on the ground and expel fire extinguishing foam
from the underside of the crash crew trucks to put out the fire).
The Crash Crew was a 24/7/365 operation and monitored the airport
control tower's VHF Low Band (I don't remember the frequency but it
was VHF Low Band between 30 to 49 MHz).  One bright sunny early
afternoon in June 1968 all of a sudden over the radio came the loud
and clear call "ROLL THE GEAR" "ROLL THE GEAR" which is the highest
response precedence for the Crash Crew to man the crash crew trucks
and head for the airport crash site.
So, without hesitation the Argentia Newfoundland Crash Crew
immediately manned the crash crew trucks and headed for the airport
except they saw no evidence of a crash.  There was no smoke or fire.
The senior on-scene crash crew member called the tower and asked if
this was a drill?  The tower replied they also heard the "ROLL THE
GEAR" call but it was not them and for the crash crew to return to
Later that day it was determined that the "ROLL THE GEAR" call was
actually from the U.S. Naval Air Station in Rota, Spain, over 2,500
miles away!  Both Argentia and Rota used the same VHF Low Band
Thanks for bringing back the fond memories of over 52 years ago."
For more information concerning radio propagation, see and the ARRL Technical Information
Service 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
Instructions for starting or ending email distribution of ARRL
bulletins are at
Sunspot numbers for August 13 through 19, 2020 were 11, 0, 0, 0, 0,
12, and 15, with a mean of 5.4.  10.7 cm flux was 72.3, 70.8, 70.6,
70.9, 70.8, 71.3, and 70.5, with a mean of 71.  Estimated planetary
A indices were 4, 4, 3, 4, 3, 7, and 6, with a mean of 4.4.  Middle
latitude A index was 5, 3, 3, 5, 3, 7, and 9, with a mean of 5.


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