Solar activity reached high levels this past week when Region 4299
produced an M1.1 (R1/Minor) flare on December 6. Shortly after, the
region produced an M8.1/2b (R3/Strong) flare, also on December 6.
Associated with the M8.1 flare was a 1,100 SFU Tenflare, a 1,143
km/s Type II sweep and a Type IV sweep. (A “sweep” is a solar radio
burst that sweeps through the RF spectrum as the energy moves
outward from the Sun.)
Some development was observed around the leader spot of Region 4299,
while slight decay was noted among the trailer spots. Regions 4296
and 4294 remained the largest of the visible disk but have only
produced C-class activity in the past 24 hours. Only minor changes
were observed among the other numbered active regions and activity
is now moderate.
Coronal mass ejection (CME) activity was observed from both M-class
flares. A slow, Earth-directed CME was observed from the M1.1 and a
faster, full-halo, Earth-directed CME was observed from the M8.1
flare. According to Spaceweather.com, it touched off a G2 (moderate)
geomagnetic storm on December 10.
Solar wind parameters reflected a disturbed near-Earth environment
throughout the reporting period. Solar wind speeds showed little
reaction to the magnetic transient, averaging 375 km/s throughout
the reporting period. The phi angle was oriented towards-the-Sun
(negative) for the majority of the reporting period, then slowly
rotated around to away-from-the-Sun (positive) 1.5 hours after the
arrival of the transient.
The electron flux is expected to become elevated through December 14
as a coronal hole high speed stream (CH HSS) originating from the
negative polarity coronal hole in the northern hemisphere becomes
geoeffective. The flux is likely to surpass the 1,000 pfu threshold
during the diurnal maxima.
As complex regions in the western hemisphere move beyond the limb,
chances for the proton flux to become elevated decrease. There is a
10% chance for an S1 (Minor) radiation storming event on December
12, with chances decreasing to 1% by December 14.
Spaceweather.com for December 12 reports on the Geminids Meteor
Showers peaking this upcoming weekend.
A story on the Meteor Scatter QSO Party can be found on the ARRL
website at,
.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere, December 4, 2025, by F. K. Janda, OK1HH:
“On December 1, an active sunspot group emerged on the southeastern
limb of the solar disk, as expected. During the last solar rotation,
it was designated AR4274. Astronomers renamed it now as AR4294,
while produced the first in a series of energetically significant
flares observed during the first third of December. In addition,
AR4296 began to grow right next to it, and together they began to
resemble the so-called Carrington region of 1859. However, the
growth of both regions slowed down, but moderately powerful
eruptions continued to occur in them, surprisingly contributed to by
the relatively small group AR4299 in the north of the solar disk.
“Another energetically significant solar flare on December 8 came as
a surprise. Given the speed of the ejected particles, the CME was
expected to hit Earth on December 9. However, they apparently
traveled to Earth along a longer path and arrived on December 10.
Therefore, they encountered a slow and expected stream of particles
that last hit Earth on November 12. The result of the encounter
between the slow and fast particle streams was a so-called reverse
shock at around 20:00 UT on December 10, which triggered a G2-class
geomagnetic storm. However, these storms are usually short-lived
and, apart from unusual, irregular (and interesting) developments,
they did not have any significant consequences.
“Solar activity remains high, and the state of the ionosphere
reflects this. However, the fact that the conditions for shortwave
propagation are different from previous cycles is another story.
Every eleven-year cycle is different.”
The latest video from Dr. Tamitha Skov, WX6SWW, can be found on
YouTube at, .
The Predicted Planetary A Index for December 13 to 19 is 12, 12, 8,
5, 8, 10, and 8, with a mean of 9. Predicted Planetary K Index is
4, 4, 3, 2, 3, 3, and 3, with a mean of 3.1. 10.7-centimeter flux
is 140, 130, 130, 135, 135, 140, and 140, with a mean of 135.8.
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
. Information and
tutorials on propagation can be found at, .
Also, check this:
https://bit.ly/3Rc8Njt
“Understanding Solar Indices” from September 2002 QST.