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ARRL Propagation Bulletin ARLP005 (2021)

ARLP005 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 5  ARLP005
From Tad Cook, K7RA
Seattle, WA  January 29, 2021
To all radio amateurs 

ARLP005 Propagation de K7RA

Solar activity increased this week. We saw no spotless days, and
the average daily sunspot number rose from 14.7 to 28.1. Average daily
solar flux was up from 76.1 to 77.2.

Average daily planetary A index rose from 4 to 9.4 due to a minor
geomagnetic storm on Monday. On that day Alaska's High Latitude
College A index was 33.

Predicted solar flux for the next 30 days is 76, 75, 74 and 74 on
January 29 Through February 1, then 72, 70, 70 and 72 on February
2-5, 76 on February 6-10, 77 on February 11-20, 76 on February
21-24, 75 on February 25-27.

Predicted planetary A index is 5, 5 and 8 on January 29-31, then 18,
12 and 8 on February 1-3, 5 on February 4-6, 10 on February 7-8, 5
on February 9-19, then 8, 12 and 12 on February 20-22, and 5 on
February 23-27.

Even after a nice stretch of days with sunspots, 10.7 cm solar flux
seems weak. Last week and this week we reported average daily solar
flux of 73.8 and 78.6. But toward the end of 2020, the three
bulletins reporting data from November 19 through December 9 had
average daily solar flux at 90.1, 108.1 and 91.9.

On Thursday reported a sunspot number of 26 and
showed an image of two active regions on the Sun, 2800 and 2797, but
NOAA SESC showed a sunspot number of 0 for the same day, reported
at, .

Perhaps this will be corrected after this bulletin is released. That
DSD.txt file is the only source used for sunspot numbers reported in
this bulletin.

Geomagnetic activity forecast for the period January 29 to February
24, 2021 from F.K Janda, OK1HH.
"Geomagnetic field will be:
quiet on: January 29-31, February 4, 10, (24)
quiet to unsettled on: February 5-6, 9-13, 17, 19
quiet to active on: February 1, 3, 7, 14-16, 18, 20, 22-23
unsettled to active: February (2, 8, 21)
active to disturbed: none predicted

"Solar wind will intensify on January (31,) February (1,) 2-3, (4,
8-10, 15-17, 20-21,) 22-24, (25).

"Parenthesis means lower probability of activity enhancement. The
predictability of changes remains low, as indicators are ambiguous."

An article about tree rings as an indicator of historical solar
activity can be found online at:

This weekend is the CW portion of the CQ 160 meter contest.
Geomagnetic activity is quite low, which is a favorable indication
for 160 meters. See for rules.

Imagine, if you will, the worst possible solar flare, maybe worse
than the infamous Carrington Event, the one that made aurora visible
all the way down to the equator and set fire to telegraph offices.
Some smart people have done just that. Try not to scare yourself:

Check out last weekend's Propagation Summit:

Dr. Tamitha Skov, WX6SWW, has a new mini-course:

KA3JAW enjoys monitoring the FM broadcast band and the 11 meter band
for E-skip. He reported from Pennsylvania:

"Nothing heard on the FM band, but Monday, January 25th was a great
radio day for both single-hop and double-hop sporadic-E (Es) on 11

"The spectacular event started early in the morning, 6:45 AM (1145
UTC) till late afternoon - 4:54 PM (2154 UTC).

"It all began with reception of short-hop Es into southern Maine at 7
AM.  Signal was 20dB over S9 at a range of 300+ miles.

"At 2 PM, double-hop Es western stations were heard, AZ, CA, UT, WA
and Alberta, Canada.

"And if that was not enough, I was hearing west coast stations
calling out to HI.

"Around 3:45 PM, western states, southern Texas (Houston, San
Antonio, Waco) along with Florida (Tampa) were heard.

"Twenty-one states, two Canadian and one Mexican station were heard:

"AL, AZ, CA, CT, FL, GA, IA, IN, KY, LA, ME, MI, MS, NC, OH, SC, TN,
TX, UT, VA, and WA.

"In Canada: Ontario, Alberta.

"In Mexico: Tijuana."

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

For more information concerning radio propagation, see and 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

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

Sunspot numbers for January 21 through 27, 2021 were 26, 39, 34, 23,
26, 23, and 26, with a mean of 28.1. 10.7 cm flux was 77.6, 78.2,
77.9, 77.6, 77.1, 75.7, and 76.3, with a mean of 77.2. Estimated
planetary A indices were 3, 4, 5, 5, 17, 21, and 11, with a mean of
9.4. Middle latitude A index was 2, 3, 3, 4, 14, 9, and 9, with a
mean of 6.3.


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