Message 28937 in PROP.ARL
From: NC8Q
Date: Fri, 28 Aug 26 17:24:00 Z
Newsgroups: PROP.ARL
Subject: ARLP035 Propagation Forecast
Message-ID: <ARLP035>
Path: N2NOV|K7EK|KI0BK|N5MDT|NC8Q
R:260828/1738z @:N2NOV.#RICH.NY.USA.NOAM $:ARLP035
R:260828/1737z @:K7EK.#NOKY.KY.USA.NOAM $:ARLP035
R:260828/1736Z 31874@KI0BK.#NEKS.KS.USA.NOAM LinBPQ6.0.24
R:260828/1724Z 4203@N5MDT.#STX.TX.USA.NOAM BPQ6.0.25
R:260828/1724Z 52375@NC8Q.#DAY.OH.USA.NOAM LinBPQ6.0.25
ZCZC AP35
QST de W1AW
Propagation Forecast Bulletin 35 ARLP035
>From ARRL Headquarters
Newington, CT August 28, 2026
To all radio amateurs
SB PROP ARL ARLP035
ARLP035 The ARRL Solar Report
Solar activity reached moderate levels this week. Region 4513 was responsible for an M2.2/1B flare that reached its peak on Aug
ust 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 (C
ME) 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 imagerie
s on August 25.
The first event likely originated from the vicinity of Region 4513 around August 25 while no definitive source could be identif
ied with any confidence for the latter. Nevertheless, both of these events are currently being modeled and assessed to determin
e 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 Augu
st 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 ho
le 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, includ
ing flare activity we have been observing moderate-sized flares since August 24, peaking on August 25. Most sunspots and all la
rger groups are now located in the western half of the solar disk, which increases the likelihood of rising geomagnetic activit
y, 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. Geoma
gnetic activity, however, will increase, whilst is likely to remain higher for the rest of August. Consequently, shortwave prop
agation conditions will no longer be as consistent as in recent days; instead, there will be a decrease in usable frequencies a
nd an increase in attenuation. The beginning of September will be calmer, albeit with slightly lower critical frequencies in th
e 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 Plan
etary 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, an
d 115 with a mean of 119.3.
For more information concerning shortwave radio propagation, see www.arrl.org/propagation and the ARRL Technical Information Se
rvice web page at www.arrl.org/propagation-of-rf-signals. For an explanation of numbers used in this bulletin, see www.arrl.org
/the-sun-the-earth-the-ionosphere. Information and tutorials on propagation can be found at http://k9la.us.
Also, check this: "Understanding Solar Indices" from September 2002 QST. https://bit.ly/3Rc8Njt
NNNN
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