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The K7RA Solar Update



"A glancing blow from a recent CME is expected to arrive late on UT
day 28-Jun. Additional to this, solar wind parameter Bz has been
oriented southward for approximately 15 hours. Combined this may
induce G1 geomagnetic conditions. A second CME is expected to arrive
late on UT day 29-Jun and may also cause G1 geomagnetic conditions.


Nine new sunspot groups emerged over this reporting week, June

Two appeared on June 21, four on June 23, two more on June 25 and
one on June 26.

Average daily sunspot number declined from 149.6 to 141.6, but
average daily solar flux increased from 178 to 195.1.

Average planetary A index declined from 10.3 to 7.

Predicted solar flux for the near term is 182 on June 28-30, then
180, 185, 180, 175, and 190 on July 1-5, 180 on July 6-7, then 165,
165 and 180 on July 8-10, 170 on July 11-13, then 180, 190 and 195
on July 14-16, then 200 on July 17-18, 195 on July 19-20, 190 on
July 21-28, then 195, 190, 185 and 190 on July 29 through August 1,
and 180 on August 2-3.

Predicted planetary A index is 12 and 15 on June 28-29, 5 on June 30
through July 13, then 10, 10 and 8 on July 14-16, 5 on July 17-19, 8
on July 20, then 5 on July 21-26, 8 on July 27-28, and 5 on July 29
to August 9.

Geomagnetic activity forecast for the period June 28 - July 04,
2024, from Tomas Bayer, RWC Prague, Institute of Geophysics of the
ASCR, Prague, Department of Geomagnetism Budkov observatory (BDV):

"Quiet: June 30 to July 1, 3 and 4

"Unsettled: June 28 and 29, July 1 and 2

"Active: possible June 28 and 29, July 2

"Minor storm: 0

"Major storm: 0

"Severe storm: 0

"Next week, we expect quiet to unsettled conditions. Two unsettled
to active events are possible next week.

"The first one is possible about June 28 - 29, and the other one,
but unlikely, about July 2. Other days, we expect quiet to unsettled

George Hoffman, W7POE, wrote in an email:

"A question some of us have is, with the quite high SFI and SSN
numbers, why is the MUF around the Washington state region never
much above 21 MHz these days? For me 10 meters was totally dead
during Field Day. I haven't seen MUFs in the 30 MHz region for
several weeks now. Wonder if you could shed some light on this
puzzling issue. Thanks."

I replied that I suspect this is because of seasonal variation.

I used the W6ELprop program to estimate MUF over a specific path
(Dallas, Texas from Seattle) with an estimated smoothed sunspot
number of 133.

For the current date (June 27) it shows the MUF at about 22 MHz, day
and night.

But when I change the date back closer to the Spring Equinox (just
before March 28), the MUF is highest from 2030-2100 UTC at 34.7 MHz.

It also shows MUF above 28 MHz from 1530-0230 UTC.

George also shared a very useful link:

George replied:

"I also just ran W6ELprop and got 22 MHz for the Burien to Dallas
path and 17.6 MHz for the Burien to New York path. Anyway, I will
wait around for 10 meter openings.  Thanks again."

William Paul, KD6JUI, of Dixon, California wrote in an email:

"I was operating from my kayak again on Field Day.  10 watts into a
homebrew loop. My ops were all SSB.

"Only heard one (1!) station on 10m, so all my operating was
confined to 15m. I had enough exchanges to keep me happy but there
was a lot of fading. Didn't hear any foreign stations coming in.

"Did get some fine photos of bees pollinating water flowers.

"Maybe if Field Day were held in December and with the same high
solar flux, 15 and 10 meters would've been a lot more active."

K7RA comment: "There is Winter Field Day in January."

NASA images:

Solar max and climate:

Active sunspot returns:

Big sunspot:

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 about Solar Indices:

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

Sunspot numbers for June 20 through 26 2024 were 138, 133, 139, 176,
141, 129, and 135, with a mean of 149.6. 10.7 cm flux was 203.3,
196.9, 195.7, 195.8, 198.7, 193.7, and 181.4, with a mean of 178.
Estimated planetary A indices were 7, 5, 4, 10, 5, 9, and 9, with a
mean of 10.3. Middle latitude A index was 8, 4, 6, 12, 7, 9, and 8,
with a mean of 10.1.




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