08/28/2026
Solar activity reached moderate levels this week. Region 4513 was responsible
for an M2.2/1B flare that reached its peak on August 26. This event was
accompanied by a 10.7-centimeter radio burst that reached 140 solar flux units
(SFU) and a type II radio sweep with an estimated shock speed of 930 km/s
despite its relatively impulsive nature. No resulting coronal mass ejection
(CME) has been observed in available coronagraph imagery as of the time of this
report.
Other activity of note since the last reporting period included an easterly CME
first seen in two LASCO C2 coronagraph imageries on August 25.
The first event likely originated from the vicinity of Region 4513 around August
25 while no definitive source could be identified with any confidence for the
latter. Nevertheless, both of these events are currently being modeled and
assessed to determine the presence of an Earth-directed path.
Solar activity will likely remain at minor-moderate (R1-R2) levels, with a
slight chance for strong (R3) activity, through August 28, mostly due to the
flare history and potential of Region 4513.
Solar wind parameters were at undisturbed levels with solar wind speeds between
~300-340 km/s, total field at or below 5 nT and Bz northward or near neutral.
Phi angle was predominantly negative.
Nominal solar wind conditions are expected to continue until midday August 27,
when the onset of a positive polarity coronal hole high speed stream (CH HSS)
influence is anticipated. Additional solar wind disturbances, with increased
solar wind densities and total IMF, are likely on August 28 due to the impact of
the CMEs that left the Sun on August 25.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere,
August 27, 2026, by F. K. Janda, OK1HH:
More or less in line with expectations, total solar activity has been slightly
elevated during the last third of August, including flare activity we have been
observing moderate-sized flares since August 24, peaking on August 25. Most
sunspots and all larger groups are now located in the western half of the solar
disk, which increases the likelihood of rising geomagnetic activity, which had
been low for a relatively long period beginning on August 21. This resulted in
above-average shortwave propagation conditions, including propagation in the
Earth s polar regions.
Solar activity is expected to remain elevated for the remainder of August and
will drop significantly in early September. Geomagnetic activity, however, will
increase, whilst is likely to remain higher for the rest of August.
Consequently, shortwave propagation conditions will no longer be as consistent
as in recent days; instead, there will be a decrease in usable frequencies and
an increase in attenuation. The beginning of September will be calmer, albeit
with slightly lower critical frequencies in the F2 layer of the ionosphere.
The Predicted Planetary A Index for August 28 to September 3 is 10, 8, 5, 5, 5,
5, and 5 with a mean of 6.9. The Predicted Planetary K Index is 3, 3, 2, 2, 2,
2, and 2 with a mean of 2.3. Predicted 10.7 centimeter flux is 120, 120, 120,
120, 120, 120, and 115 with a mean of 119.3.
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
[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
---
■ Synchronet ■ Whiskey Lover's Amateur Radio BBS
|
