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ARRL Propagation Bulletin ARLP012 (2020)

ARLP012 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
From Tad Cook, K7RA
Seattle, WA  March 20, 2020
To all radio amateurs 

ARLP012 Propagation de K7RA

On Wednesday, reported a new emerging Solar Cycle 25
sunspot in the Sun's Northern Hemisphere, but it was not yet
numbered. By the next day (yesterday) it had already faded away into

In last week's Propagation Forecast Bulletin ARLP011 we reported
sunspots on just two days, March 8 and 9.

Average daily sunspot number over this reporting week (March 12-18)
declined to 0 from 3.6, and daily solar flux values barely
changed from 70.2 to 70.1. Geomagnetic averages were quiet but
higher, with planetary A index changing from 4.4 to 5.9 and middle
latitude A index from 3.6 to 4.1.

Predicted solar flux for the next 45 days is 72 on March 20-27, 70
on March 28 til April 4, 72 on April 5-18, 70 on April 19 til May 1,
and 72 on May 2-3.

Predicted planetary A index is 8 on March 20-23, 5 on March 24-27,
then 8 on March 28, 5 on March 29 til April 5, then 10 and 8 on
April 6-7, 5 on April 8-13, then 8, 12 and 8 on April 14-16, 5 on
April 17-22, then 12 and 8 on April 23-24, and 5 on April 25 til May
2 and 10 on May 3.

We have been looking forward to the Vernal Equinox, which occurred
at 0350 UTC today, March 20. Of course, depending on where you are,
the arrival of Spring may have been reported as yesterday, but here
we are referring to the date as Friday because of UTC. So that is
the same as 8:50 PDT or 11:50 EDT on Thursday,

This is a favorable time for HF propagation, with both the northern
and southern hemispheres receiving an approximately equal amount of
solar radiation. has some of the finer details on the beginning of Spring
2020, and an article about sunspots.

Geomagnetic activity forecast for the period March 20 to April 15,
2020 from F.K. Janda, OK1HH:

"Geomagnetic field will be
quiet on: April 10
quiet to unsettled on: March (20-26,) 29-30, April 2-5, 7, 11-13
quiet to active on: (March 28, 31, April 1, 6, 8-9)
unsettled to active on: (March 27, April 14-15)
active to disturbed: never

"Solar wind will intensify on: March 28, (29-31, April 9, 13).

- Parenthesis means lower probability of activity enhancement.
- The predictability of changes remains lower as there are no

A couple of resources I am finding useful for real time reporting of
propagation on various bands, modes and times, from 24 hours ago til
present time:

The latest from Dr. Tamitha Skov, the Space Weather Woman:

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 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

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 March 12 through 18, 2020 were 0, 0, 0, 0, 0, 0,
and 0, with a mean of 0. 10.7 cm flux was 69.9, 68.8, 68.1, 70.2,
69.8, 71.6, and 72, with a mean of 70.1. Estimated planetary A
indices were 7, 7, 3, 5, 7, 6, and 6, with a mean of 5.9. Middle
latitude A index was 7, 6, 2, 3, 3, 4, and 4, with a mean of 4.1.


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