07/11/2025
Spaceweather.com reports solar activity was at low levels with only C-class
flares observed. The largest flare during the period was a C8.9 from an
unnumbered region beyond the east limb at S13. This region was also
responsible for the majority of the remaining flares alongside Regions 4136 and
4137.
An approximate M2 was observed by Solar Orbiter at 10/1326 UTC just beyond the
east limb, brightening can be seen in the SUVI-94 channel at this time. A slow
moving CME was observed in coronagraph imagery, modelled and was determined to
not have any impact.
Solar activity is expected to be low with a chance for M-class flares, minor to
moderate, through 13 July, primarily due to the flare potential of Region 4136.
Solar wind parameters remained at nominal conditions. Total field was 2-5 nT
with the Bz component between +/-4 nT. Solar wind speeds were between 350-400
km/s. The phi angle was variable after 10/0500 UTC.
Nominal solar wind conditions are expected through 11 July. The co-rotating
interacting region associated with a positive polarity CH HSS is expected to
arrive 12 July, an enhancement of the solar wind parameters will follow the
arrival and remain enhanced thereafter.
Mostly quiet conditions are expected 11 July. Unsettled to active conditions
are likely starting 12 July as Earth moves into a geoeffective position with a
positive polarity CH HSS.
There is a decreased chance for minor to moderate radio blackouts on 11 July
with most regions on the visible disk rotating off and no appreciable spot
groups rotating on. Conditions could increase on 12 or 13 July as old Regions
4117, 4118, 4120, and 4121 rotate back onto the visible disk.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere
July 6 and 10, 2025
Although solar activity is lower this year than it was last year, it is still
at the maximum level of the eleven-year cycle. Moreover, it is quite possible
that it will increase further this year. This is indicated by the continuing
slight predominance of activity in the northern half of the solar disk, while
in the southern half we more often observe relatively large coronal holes. The
active regions are mostly simple (magnetic type alpha or beta) and therefore,
with a few exceptions, do not show significant eruptive activity.
Although solar flares have not been powerful recently, they are quite often
accompanied by CMEs. When ejected particles hit Earth, it is often three to
four days after the CME is observed, instead of the usual two to three days.
This is one reason why the error in predicting the arrival time of the particle
cloud is slightly increasing. This is especially true when their source is on
the far side of the Sun.
The solar wind has finally slowed down in recent days (from speeds of over 800
km/s observed not long ago to less than 400 km/s now) and the interstellar
magnetic field has weakened, which has finally had a positive effect on the
state of the Earth's ionosphere, as well as the shortwave propagation
conditions. Although the arrival of a high-speed stream from a recurring
coronal hole with negative polarity can be expected from July 4, causing
unstable geomagnetic conditions, the phenomenon should not last long. In
addition, the low flux of electrons with energies greater than 2 MeV is likely
to remain, so a return to fairly favorable conditions can be expected.
In connection with the occurrence of a large coronal hole in the southeastern
part of the solar disk, slightly increased geomagnetic activity can be
expected. In the coming days (starting July 13-14), it may reach level G1.
On the above-mentioned days (July 13 to 14, or 1 to 2 days later), the negative
impact on the ionosphere could be intensified by declining solar activity.
Further developments cannot be predicted with greater accuracy, but the
probability of disturbances will be higher in the last third of July.
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation[1] and the ARRL Technical Information Service
web page at, http://arrl.org/propagation-of-rf-signals[2] For an explanation
of numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere[3] . Information and tutorials
on propagation can be found at, http://k9la.us/[4] .
Also, check this:
https://bit.ly/3Rc8Njt[5]
"Understanding Solar Indices" from September 2002 QST.
The Predicted Planetary A Index for July 12 to 18 is 10, 8, 8, 12, 12, 10, and
10, with a mean of 10. Predicted Planetary K Index is 4, 3, 3, 4, 4, 4, and 4,
with a mean of 3.7. 10.7 centimeter flux is 105, 105, 110, 115, 120, 125, and
125, with a mean of 115.
[1] http://www.arrl.org/propagation
[2] http://arrl.org/propagation-of-rf-signals
[3] http://arrl.org/the-sun-the-earth-the-ionosphere
[4] http://k9la.us/
[5] https://bit.ly/3Rc8Njt
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