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The K7RA Solar Update


Average daily solar flux values dropped over the past week, but
sunspot numbers were nearly the same, comparing May 25 to 31 to the
previous week.

Average daily solar flux declined from 161.2 to 155.3. Geomagnetic
indicators were quieter, with average daily planetary A index
declining from 17.1 to 7.3, and middle latitude numbers from 14.4 to

Predicted solar flux is 160 on June 2, 155 on June 3-4, 150 on June
5-8, 130 on June 9-11, then 135, 140, 143, 145, and 150 on June
12-16, 155 on June 17-20, 150 on June 21-25, then 145, 140 and 135
on June 26-28 and 130 on June 29 to July 8.

Predicted planetary A index is 15, 12, 10 and 8 on June 2-5, 5 on
June 6-17, then 22, 15, 12 and 10 on June 18-21, 5 on June 22-24, 12
and 10 on June 25-26, then 5 on June 27-28, then 15, 12, 15, 10 and
8 on June 29 through July 3, then 5 on July 4 through the middle of
the month.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - June 1, 2023 from OK1HH:

"The Sun still surprises us, it has been in the habit for billions
of years, but we only observe it for a few hundred years. So, we
have a right to be surprised by what it is doing and what we can
observe with instruments on satellites and powerful solar telescopes
on Earth, including the largest four-metre one on the island of Maui
in Hawaii, which can see the very fine structures of sunspot nuclei.

"What's more, we're seeing spots on the far side of the Sun that are
so big, they affect the vibration of the whole Sun. But we can only
see their structure and predict possible flares after they appear on
the eastern limb of the solar disk, which was not at all the case
with the current most active AR3315, which did not appear there. It
emerged later, thereafter began to grow rapidly.
"Conversely, the source of the next big flare was hidden behind the
southeastern limb, and we only saw the prominence above it.

"Meanwhile, the larger groups of sunspots have mostly moved to the
western half of the solar disk. A large coronal hole in the southern
hemisphere now crosses the central meridian. This increases the
likelihood of geomagnetic disturbances starting on June 2."

Mike, AK7ML wrote:

"I recall in a movie about Pearl Harbor that they could not reach
Hawaii from stateside on HF and then they sent the message by cable
telegraph in routine status, so Pearl was not informed of the attack
in time.

"For years I have been able to work Australia in the morning and now
it is Indonesia that is workable instead!"

A story about a big sunspot:

I've added information from this resource to the text appearing at
the bottom of every propagation forecast bulletin (this resource
comes from September 2002 QST):

I was sad to learn that old friend Chip Margelli, K7JA became a
Silent Key on May 25. Chip was from the Seattle area, and first came
to my attention when he became proficient in the Japanese language
during high school, then specialized in running JA stations at the
old Rush Drake, W7RM contest station on Foulweather Bluff in Puget
Sound.  At one time he may have been the most famous American ham in
Japan, or so I heard at the time.

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 .

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 May 25 through 31, 2023 were 121, 127, 125, 119,
153, 144, and 147, with a mean of 133.7. 10.7 cm flux was 152.1,
149, 156.9, 151.3, 154.4, 162, and 161.4, with a mean of 155.3.
Estimated planetary A indices were 11, 6, 4, 11, 4, 5, and 10, with
a mean of 7.3. Middle latitude A index was 11, 6, 5, 11, 5, 6, and
11, with a mean of 7.9.




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