Key solar indicators were lower this week, with average daily solar
flux down from 194.3 to 170.5 and average daily sunspot numbers
declining from 129.3 to 127.7.

On October 22, Spaceweather.com reported:

"THE SUN IS TAKING A QUICK BREAK: Solar Max is hard work. Just ask
the Sun. After flaring almost without pause for the past 10 months,
the Sun is taking a quick break. Solar activity has been low for the
past 48 hours with no flares stronger than category C. The quiet
won't last. Solar Max is expected to continue for at least another
year; flaring should resume shortly."

Predicted solar flux is 200 on October 25-26, then 205 and 215 on
October 27-28, then 220 on October 29-31, then 180, 185, 180 and 175
on November 1-4, 180 on November 5-6, 185 on November 7-8, 180 on
November 9, 175 on November 10-12, then 180 and 175 on November
13-14, 170 on November 15-16, 165 on November 17-18, and 160 and 165 on November 19-20.

Predicted planetary A index is 15, 18 and 7 on October 25-27, then 8
on October 28-29, 5 0n October 30 through November 10, then 12, 12,
8, 5, 12, 10, 5, 15 and 10 on November 11-19, and 5 on November
20-21, 12 on November 22 and 5 on November 23-30.

"Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere - October 24, 2024 from F.K. Janda, OK1HH:

"NASA and NOAA announced in a joint statement on October 15, 2024
that a solar maximum is underway. This phase of the cycle may take 2
to 3 years to develop. For shortwave propagation, this implies that
the regular openings of the shortest bands will continue at least
through 2025, possibly longer.

"The author of these lines considers it likely that the current
11-year cycle will have two peaks, the first of which is taking
place now. In that case, we could expect the second peak in 2025.

"Coronagraphs aboard artificial Earth satellites provide invaluable
data for predicting solar activity. The Solar and Heliospheric
Observatory (SOHO) has been in operation for an unexpectedly long
time - it was launched in December 1995! Fortunately, the Sun is
still being similarly observed by GOES-19, although it is still
undergoing testing with instrument checks, including the
coronagraph, which we expect to be in regular use from Spring 2025.

"In the last two weeks or so, we have been able to observe the size
of AR3842 and AR3844 on the Sun's far side.

"AR3844, meanwhile, emerged on the southeastern limb of the solar
disk, was renamed AR3869, and immediately made itself known with a
powerful solar flare of class X3.3. It happened on October 24, with
the peak of the event at 0357 UT. The extreme ultraviolet radiation
from the flare ionized the upper part of the Earth's atmosphere. The
Dellinger effect knocked out shortwaves to 30 MHz for nearly an hour
in the Australia and Southeast Asia region. The current CME has left
the Sun, but is unlikely to hit Earth (if it does, it could happen
on October 26).

"After the eruption, due to the increase in ionization of the
ionospheric F2 region between 0910 - 1050 UT, the 50 MHz magic band
between central and southern Europe and Japan (especially the
southern half of its large islands) was opened. However, the vast
majority of contacts were established at 50313 kHz (WSJT-X, FT8)."

Send your tips, reports, observations, questions and comments to
k7ra@arrl.net. 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 and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals. For
an explanation of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere .

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

Also, check this article:

https://bit.ly/3Rc8Njt

"Understanding Solar Indices" from September 2002 QST.

Instructions for starting or ending email subscriptions to ARRL
bulletins are at http://arrl.org/bulletins .

Sunspot numbers for October 17 through 23 2024 were 146, 132, 101,
113, 168, 130, and 104, with a mean of 127.7. 10.7 cm flux was
167.7, 173.5, 165.2, 161.7, 163.9, 176.1, and 185.7, with a mean of
170.5. Estimated planetary A indices were 9, 14, 23, 7, 5, 8, and 9,
with a mean of 10.7. Middle latitude A Index was 7, 10, 15, 6, 3, 7,
and 7, with a mean of 7.9.