Subj : The K7RA Solar Update
To   : QST
From : ARRL de WD1CKS
Date : Mon Jul 31 2023 10:10 pm

07/28/2023

�Average daily sunspot numbers declined slightly over the past week (July
20-26) to 128.1, compared to 130.6 over the previous seven days.

Average daily solar flux declined significantly from 190.5 to 172.2.

The solar flux forecast sees values at 165 and 162 on July 28-29, 158 on July
30-31, then 155 on August 1-3, then 165, 170 and 175 on August 4-6, 180 on
August 7-10, 175 on August 11-13, 180 on August 14-15, 175 on August 16-18, 170
on August 19, then 165, 165 and 160 on August 20-22, and 155 on August 23-26,
160 on August 27, 165 on August 28-30, 170 and 175 on August 31 through
September 1, and 180 on September 2-6.

Predicted planetary A index is 5 on July 28-29, 15 and 10 on July 30-31, 5 on
August 1-3, 8 on August 4, 5 on August 5-9, 10 on August 10, 8 on August 11-13,
5 on August 14-19, then 10, 8 and 5 on August 20-22, 12 on August 23-24, 10 on
August 25-26, 5 on August 27-29, 10 and 8 on August 30-31, and 5 on September
1-5.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere --
July 27, 2023 from OK1HH.

"The likelihood of more massive solar flares has slowly decreased in recent
days as large groups of spots have fallen behind the western limb of the solar
disk and the magnetic configuration of the �remaining regions has become
increasingly simple over the past few days.

On July 20 and 21, two CMEs struck Earth's magnetic field in accordance with
the prediction. However, both impacts were weak and did not produce even a
minor geomagnetic storm.

Another weak halo CME was expected to leave the Sun on 23 July at about 1530
UTC in a C5 class flare in spot group AR3376, coinciding with the outburst of a
relatively nearby magnetic filament. The Earth's magnetic field detected its
arrival at 0200 UTC on 26 July. The result was an increase in geomagnetic
activity and a deterioration of shortwave propagation conditions. The
disturbance actually started on 25 July at 2235 UTC, but it was not clear
whether it was an early arrival of the same CME or another one that we did not
detect.

Note: since I will be abroad next week, I will not post the next comment on
August 3, but on August 10."

Sunspots, flares and aurora.� https://bit.ly/44JxcRp[1]

Mars Rover sees the far side of the sun.� https://bit.ly/3KbRV8b[2]

Rocket punches hole in ionosphere.� https://bit.ly/3KceBFB[3]

Nearly five decades ago I witnessed the same thing, viewed from Marin County,
California. It was a huge dramatic display, My friend had seen it before, and
said it was created by a rocket launch from Vandenberg AFB in Southern
California.

Another CME.� https://bit.ly/44LhRjx[4]

On July 27, Spaceweather.com sent this alert:

"A STRONG FARSIDE CME JUST HIT SOLAR ORBITER: Europe's Solar Orbiter just got
hit by the kind of CME that may have once caused a major power blackout on
Earth. This time, Earth was not in the line of fire. It was a farside eruption
that flew away from our planet. Maybe next time?"

Massive flare?� https://bit.ly/3Ya7OSC[5]

Latest from Dr. Tamitha Skov.� https://youtu.be/cD5VbWvBXsE[6]

Send your tips, reports, observations, questions and comments to
[email protected][7] . When reporting observations, don't forget to tell us which
mode you were operating.

For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation[8] �and the ARRL Technical Information Service
at http://arrl.org/propagation-of-rf-signals[9] . For an explanation of numbers
used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere[10]

Also, check this article from September, 2002 QST:

https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf[11]

An archive of past propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation[12] . More good information
and tutorials on propagation are at http://k9la.us/[13]

Instructions for starting or ending email distribution of ARRL bulletins are at
http://arrl.org/bulletins[14]

Sunspot numbers for July 20 through 26, 2023 were 131, 121, 103, 117, 141, 137,
and 147, with a mean of 128.1� 10.7 cm flux was 184.3, 172.8, 174.4, 172.5,
165.1, 169, and 167.4, with a mean of 172.2. Estimated planetary A indices were
10, 13, 9, 6, 7, 11, and 21, with a mean of 11. Middle latitude A index was 10,
11, 9, 5, 8, 12, and 23, with a mean of 11.1.


[1] https://bit.ly/44JxcRp
[2] https://bit.ly/3KbRV8b
[3] https://bit.ly/3KceBFB
[4] https://bit.ly/44LhRjx
[5] https://bit.ly/3Ya7OSC
[6] https://youtu.be/cD5VbWvBXsE
[7] mailto:[email protected]
[8] http://www.arrl.org/propagation
[9] http://arrl.org/propagation-of-rf-signals
[10] http://arrl.org/the-sun-the-earth-the-ionosphere
[11] https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf
[12] http://arrl.org/w1aw-bulletins-archive-propagation
[13] http://k9la.us/
[14] http://arrl.org/bulletins

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