Subject: Weekly Highlights of Solar and Geomagnetic Activity, 25 - 31 August 2025

:Product: Weekly Highlights and Forecasts
:Issued: 2025 Sep 01 0133 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
25 - 31 August 2025

Solar activity was at low levels on 27 and 31 Aug. Activity reached
moderate levels on 25, 26, and 28-30 Aug. Region 4197 (S17, L=131, class/area-Eki/720 on 27 Aug) produced six M-class flares, the
largest being an M4.5/1n at 26/0525 UTC. Region 4199 (N04, L=115, class/area-Cao/200 on 26 Aug) produced five M-class flares, with its
largest being an M4.5 flare as well, reaching a peak at 25/0524 UTC.
This region was also responsible for a long-duration M2.7 flare at
30/1911 UTC. The associated full halo CME is forecast to arrive at
Earth sometime late on 01 Sep into early on 02 Sep.

The greater than 10 MeV proton flux at geosynchronous orbit reached
S1 (Minor) storm levels at 25/1355 UTC, observed a peak of 13 pfu at
27/0740 UTC, and decreased below threshold at 27/1510 UTC. Levels
remained enhanced, but below the 10 pfu threshold, for the remainder
of the period.

The greater then 2 MeV electron flux at geosynchronous orbit was at
high levels on 25 Aug, but returned to normal to moderate levels
from 26-31 Aug.

Geomagnetic field activity reached unsettled levels on 25-28 Aug and
again on 31 Aug. Field activity was at low levels on 29-30 Aug.

Forecast of Solar and Geomagnetic Activity
01 September - 27 September 2025

Solar activity is expected to be at low levels, with varying chances
for M-class flares (R1-R2/Minor-Moderate events) through 27 Sep.

The greater than 10 MeV proton flux levels are expected to be
slightly enhanced, but below the 10 pfu level for 01-03 Sep. There
is a chance levels could exceed the 10 pfu threshold on 01-02 Sep as
the halo CME from 30 Aug passes Earth. Conditions are then likely to
return to near background levels after 04 Sep, barring any
additional strong flare events.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at moderate levels on 01-02 Sep, 15-19 Sep, and 22-27
Sep. Flux levels are expected to reach high levels on 03-14 Sep and
20-21 Sep in association with coronal hole (CH) high speed stream
(HSS) influence.

Geomagnetic field activity is expected to reach G2 (Moderate)
geomagnetic storm levels on 01 Sep, G3 (Strong) levels on 02 Sep,
and active conditions on 03 Sep following the arrival of the halo
CME from 30 Aug. Active conditions are likely on 06-10 Sep, and
15-19 Sep with CH HSS influence. Quiet to unsettled levels are
expected on 04-05 Sep, 11-14 Sep, and 20-27 Sep.


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* Origin: NOAA Space Weather Prediction Center (3:633/280.2@fidonet)