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The K7RA Solar Update


Sunspot numbers rose this week, with the average changing from 139.4
to 149.6, but average daily solar flux only shifted from 179.2 to

Only four sunspot groups emerged this week. There was one on June 15
and three on June 19.

Average daily planetary A index only changed from 11.6 to 10.3.

Predicted solar flux is 205 and 210 on June 21-22, then 200 June
23-27, then 190, 185, and 190, on June 28-30, then 190, 195, 190,
185 and 190 on July 1-5, 180 on July 6-7, 165 on July 8-9, 180 on
July 10, then 170 on July 11-13, 175 on July 14, 180 on July 15-17,
175 on July 18-19, 190 on July 20-21, then 180, 175, 180, 190, 180,
185 and 190 on July 22-28.

Predicted planetary A index is 10, 12 and 10 on June 21-23, then 5
on June 24-29, 8 on Jun 30 to July 1, then 5 on July 2-14, then 12,
8, 8, and 5 on July 15-18, 8 on July 19-20, and 5 on July 21-26,
then 8 on July 27-28.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - June 20, 2024, from OK1HH.

F.K. Janda is going on vacation and will not have a report for us
over the next few weeks.

"Watching the Sun at its current 11-year peak of activity is
certainly not boring. On the contrary, we are experiencing quite
frequent surprises. For example, a week ago we observed an increased
attenuation of radio waves in the polar region (PCA = POLAR CAP
ABSORPTION EVENT), caused by protons coming from the far side of the
Sun. Then, on 15 June (at 1157 UTC), a cloud of particles
unexpectedly hit the Earth, triggering a weak G1 class geomagnetic

"Over the next few days, AR3712 became larger, followed by AR3713
and AR3716. All three of these large sunspot groups are already
located in the western half of the solar disk, where particles from
a possible larger flare are more likely to hit Earth. In addition,
all three regions have an unstable magnetic field and are therefore
more likely to have M- or X-class flares.

"Of the largest sunspot groups observed this cycle, two will soon
reappear on the eastern limb of the solar disk (in May they were
designated AR3663 and AR3664). The first of these will begin to
emerge on the solar disk this weekend. The second, and then largest
group, will follow a few days after that. Fortunately, solar
activity will remain high, but unfortunately, changes in propagation
conditions will be harder to predict."

From the European Space Agency:

AR3712 and flares:

Reverse magnetic field:

This video about the Sun's corona is undated:

Polar cap absorption event:

Latest videos from Dr. Tamitha Skov, WX6SWW:

This weekend is ARRL Field Day, and the forecast looks good, with
high solar flux at 200 and 190.

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 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 .

Also, check this QST article on Solar Indices:

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for June 13 through 19 2024 were 142, 117, 134, 152,
171, 150, and 181, with a mean of 149.6. 10.7 cm flux was 170.1,
169, 170.7, 167.3, 179.9, 192.7, and 196, with a mean of 178.
Estimated planetary A indices were 4, 6, 19, 13, 11, 10, and 9, with
a mean of 10.3. Middle latitude A index was 5, 8, 18, 9, 11, 11, and
9, with a mean of 10.1.




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