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The K7RA Solar Update


Solar activity was up this week, with the average daily sunspot
number increasing from 133.7 to 139, and average daily solar flux
from 155.3 to 166.8.

Average daily planetary A index stayed the same at 7.3, and average
middle latitude A index went from 7.9 to 8.6.

Predicted solar flux doesn't show any improvement, with peaks at 170
on June 23-25 and July 20-21.

The forecast shows solar flux at 168, 163, 157, 160, 157, 153, 160
and 150 on June 9-16, 155 on June 17-20, then 160 and 165 on June
21-22, 170 on June 23-25, then 168, 165 and 162 on June 26-28, 160
on June 29 through July 4, then 155, 150 and 145 on July 5-7, then
140, 135, 140, 143, 145 and 150 on July 8-13, and 155 on July 14-17.

Predicted planetary A index is 8, 5, 10 and 8 on June 9-12, 5 on
June 13-17, then 22, 15, 12 and 10 on June 18-21, 5 on June 22-26,
then 10, 12, 5 and 5 on June 27-30, then 8, 12 and 8 on July 1-3,
and 5 on July 4-7, then 10, 12 and 8 on July 8-10, and 5 on July
11-14, then 22. 15. 12 and 10 on July 15-18.

In some previous bulletins I was reporting 10 meter propagation
observed with FT8 only into Florida from my QTH in Seattle, and also
into Mexico at a similar distance.

Recently on 10 meters I am seeing propagation into VK/ZL, and in
North America mostly into Southern California, Nevada, Utah and
Arizona. Some seasonal variation, I suppose.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - June 8, 2023 from OK1HH:

"In the last seven days, solar activity has remained at a slightly
elevated level, with daily C-class flares and a few M-class flares.
This, together with the decrease in geomagnetic activity, has
resulted in a gradual increase in the daily maximum of the highest
usable frequencies of the F2 ionospheric layer. At the same time,
however, the attenuation in the lower ionospheric layers grew, which
manifested as earlier morning closures and later evening openings of
the longer shortwave bands.

"Particle clouds from CMEs during solar flares mostly did not reach
Earth - with one exception: on 7 June at 2224 UTC, the solar wind
speed jumped from 340 to 380 km/s. For a short time, the Earth's
magnetic field activity increased, usually only to K=3.

"The situation was further complicated by the sporadic-E layer,
whose season is approaching its peak.

"Inhomogeneities (non-uniformities) in the sporadic-E layer appeared
quite frequently and extended reflections were observed in the

"As a consequence, the scattering of electromagnetic waves was as
well manifested as attenuation. We are talking about the ionosphere
of the northern hemisphere of the Earth. Here we will wait for the
improvement when Summer ends there -  which fortunately will be much
earlier than Summer ends in the troposphere."

While searching for something else, I ran across this article from
the RSGB:

Mike, W9NY wrote:

"Having lived through multiple sunspot cycles since I was first
licensed in 1955, I cannot believe that 10 meters is nearly dead,
and 15 meters is minimally open. Nothing on 6 meters either.

"I discussed this with my cousin who is an astrophysicist at Oxford
who basically said, 'there are a lot of factors.' I'm just wondering
what our ham radio gurus think. I would have expected phenomenal
propagation but there is very little. Might this be related to
atomic/chemical changes in the Earth's ionosphere?"

I offered the WA4TTK Solar Data Plotting Utility as a record of
sunspot and solar flux data going back to 1989.

It can be updated weekly with a plain text file of the latest
propagation bulletin.

The data file can then be imported to any spreadsheet program for
analysis and custom graphing.

A new video from Dr. Tamitha Skov, WX6SWW:

Send your tips, reports, observations, questions and comments to When reporting observations, don't forget to tell us
which mode you were operating.

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

Also, check this article from September, 2002 QST:

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 June 1 through 7, 2023 were 143, 147, 112, 110,
151, 133, and 177, with a mean of 139. 10.7 cm flux was 163.9,
162.3, 164.6, 168.3, 169.2, 171.8, and 167.2, with a mean of 166.8.
Estimated planetary A indices were 13, 5, 5, 11, 5, 7, and 5, with a
mean of 7.3. Middle latitude A index was 14, 8, 5, 11, 6, 10, and 6,
with a mean of 8.6.




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