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ARRL Propagation Bulletin ARLP019 (2020)

ARLP019 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 8, 2020
To all radio amateurs 

ARLP019 Propagation de K7RA

We haven't seen a sunspot since Thursday, April 30 when the daily
sunspot number was 35. This is a relatively high sunspot number
based on recent activity, although not historically. In fact, the
daily sunspot number has not been as high since March 21, 2019 when
it was 49, and prior to that we need to look back further to the
previous year, when the daily sunspot number was 41 on June 22,
2018, to find a sunspot number that was as high.

This, and the fact that last week's sunspots showed the new cycle 25
polarity gives me reason for optimism. I expect solar activity to
increase and along with it, the outlook for better HF propagation.
Another reason for my optimism is that new sunspot cycles increase
at a faster rate than they decline after a activity peak has passed.

That peak of sunspot cycle 25 is expected around July, 2025, +/- 8
months, according to the latest forecast from the NOAA/NASA
International Solar Cycle Prediction Panel.

Average daily sunspot number for last week was 5, down from 8.7 the
previous seven days. The average daily solar flux rose from 69.2 to

Average daily planetary A index declined from 5.6 to 5.1, and
average middle latitude A index slipped from 5.1 to 5.

Predicted solar flux over the next 45 days is 70, every day, May 8
til June 21. In fact, that outlook for a continuous 45-day stretch
of solar flux at 70 has been the same since the May 3 prediction.

The predicted planetary A index is 5 on May 8 to 11, 8 on May 12, 5
on May 13 to 17, then 10 and 8 on May 18 and 19, 5 on May 20 to 23,
8 on May 24 to 27, 5 on May 28 to 30, then 8, 10 and 8 on May 31
through June 2, 5 on June 3 to 13, 10 and 8 on June 14 and 15, and 5
on June 16 to 21.

There you have it, a nice steady solar flux above the sixties for
the next month and a half, and stable geomagnetic conditions too.

On Thursday, May 7, reported an incoming solar wind
expected to graze our magnetic field on May 10, "causing geomagnetic
unrest at high latitudes."  Note that our planetary A index forecast
above does not show an increase until May 12.

Geomagnetic activity forecast for the period May 8 til June 2, 2020
from F. K. Janda, OK1HH.

"Geomagnetic field will be
quiet on: May 13, 26, June 2
quiet to unsettled on: May 8, 16, 25, 27 to 31
quiet to active on: (May 9, 11 and 12, 14 and 15, 20 to 22, 24, June
unsettled to active on: (May 10, 17 to 19, 23)
active to disturbed:  nothing expected

Solar wind will intensify on: May (11 and 12,) (18 to 21, 23,) 24

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

Jon Jones, N0JK reported on May 6:

"I was active on 50 MHz during the Eta Aquarid meteor shower on May

I worked W4IMD EM84 on 6 meters via meteor scatter using the digital
MSK144 mode at 1205 UTC. As W4IMD sent 73, I copied a CQ from Larry
Lambert, N0LL who was portable in rare grid DN90. I called Larry, he
copied me but we did not complete a contact.

I decoded several other stations including N4QWZ, AI5I, K0TPP, KE5Q,
and WA4CQG on meteor scatter."

Check for a dramatic video from
showing images of all daily earth-facing sunspot activity over seven
years, including approximately 93 solar rotations, compressed into
200 seconds.

Frank Donovan, W3LPL sent this fascinating information on Earth's
three north poles.

"BBC's article this week "Scientists explain magnetic pole's
wanderings" has attracted the interest of radio amateurs interested
in ionospheric propagation.

Unless you've studied geomagnetic physics you probably never
learned, or even heard, that the Earth has three north poles.  The
BBC article describes the poles very well, but does not address the
relationship between the poles and ionospheric propagation.

The geographic north pole is where the Earth's rotation axis
intersects the Earth's surface in the northern hemisphere.  It
affects ionospheric propagation because the orientation of Earth's
tilted axis to the Sun varies with the seasons and determines our
daylight/darkness cycles throughout the year.

While the magnetic north pole, the focus of the BBC article, is
important to navigation systems, it has no significance to
ionospheric propagation. Most of us learned about the magnetic north
pole when we learned how to use a compass, it is located in the
northern hemisphere where the Earth's magnetic field lines are
measured to be exactly perpendicular to the Earth's surface.  Its
position has been drifting about 50 to 60 km per year for about the
last forty years.

The geomagnetic north pole, only briefly described in the BBC
article, is very important to ionospheric propagation and many other
aspects of the Earth's space environment.  It is the intersection of
the Earth's surface in the northern hemisphere and the axis of a bar
magnet hypothetically placed at the center the Earth.  It is very
significant for ionospheric propagation because it determines the
position of the geomagnetic field in the Earth's space environment
including, very importantly, its ionosphere.  The geomagnetic field
very profoundly affects ionospheric propagation. The geomagnetic
north pole drifts only about one km.  per year, a tiny fraction of
the movement of the magnetic north pole described in the BBC

As an aside, while the magnetic north pole is drifting fairly
rapidly, the magnetic south pole is drifting very little at all."

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 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 April 30 through May 6, 2020 were 35, 0, 0, 0,
0, 0, and 0, with a mean of 5.  10.7 cm flux was 69.8, 70.2, 69.2,
68.7, 69.3, 69.3, and 69.8, with a mean of 69.5.  Estimated
planetary A indices were 2, 6, 5, 5, 6, 6, and 6, with a mean of
5.1.  Middle latitude A index was 1, 5, 3, 5, 8, 7, and 6, with a
mean of 5.


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