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The K7RA Solar Update


 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.

Mars Rover sees the far side of the sun.

Rocket punches hole in ionosphere.

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.

On July 27, 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?

Latest from Dr. Tamitha Skov.

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 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.



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