Subject: Weekly Highlights of Solar and Geomagnetic Activity, 20 - 26 October 2025

:Product: Weekly Highlights and Forecasts
:Issued: 2025 Oct 27 0243 UTC
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# Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity
20 - 26 October 2025

Solar activity was at moderate levels on 20 Oct with a single
M-class flare observed. Region 4248 (N07, L=262, class/area=Eki/380
on 17 Oct) produced an M1.1 flare, the largest of the period, at
20/0527 UTC. Region 4262 (S12, L=132, class/area=Cai/150 on 22 Oct)
produced a pair of long duration C-class flares. The first was a
C4.7 that peaked at 22/0152 UTC, with the second being a C2.7 flare
at 22/0909 UTC. Additionally, there were two far sided CMEs, likely
originating from old Region 4246 (N24, L=290, class/area=Ekc/840 on
16 Oct). These events were observed in LASCO coronagraph imagery on
21/2024 UTC. Additionally, Type II (est. 2474 km/s) and Type IV
radio sweeps were observed at 21/2011 UTC, likely associated with
the far-sided events as well. There was also a weak CME observed in
LASCO imagery on 23/1545 UTC, likely associated with a C2.1 flare at
23/1506 UTC from Region 4256 (S15, L=155, class/area=140/Dao on 18
Oct. This CME is expected to arrive at Earth on 27 Oct. Activity was
at low levels from 21-26 Oct.

No proton events were observed at geosynchronous orbit. However, the
10 MeV proton flux levels were slightly elevated on 22-23 Oct
following the far-sided CME eruptions. Conditions were at background
levels on 20-21 Oct and 24-26 Oct.

The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels from 20-26 Oct.

Geomagnetic field activity was at mostly quiet to unsettled levels
from 20-26 Oct, with the exception of an isolated active period on
25 Oct, likely associated with residual CH HSS influence.

Forecast of Solar and Geomagnetic Activity
27 October - 22 November 2025

Solar activity is expected to be at moderate levels on 31 Oct - 15
Nov due to the return of Region 4246. Low levels are expected to
prevail on 20 Oct - 30 Oct and 14 Nov - 22 Nov as multiple regions
depart the visible disk.

No proton events are expected at geosynchronous orbit from 27 Oct -
22 Nov. However, depending on the complexity of returning Region
4246, an isolated proton event is possible.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at high levels from 31 Oct - 15 Nov due to responses
from recurrent CH HSS influences. Moderate levels are expected on 27
- 30 Oct and 16 Nov - 22 Nov.

Geomagnetic field activity is expected to be at quiet to unsettled
levels on 01 Nov - 06 Nov, 10 Nov - 14 Nov, and 16 Nov - 22 Nov.
Active conditions are expected on 27 Oct and 31 Oct, 07 Nov - 09
Nov, and 15 Nov, with G1/G2 conditions likely on 28 Oct - 30 Oct due
to recurrent positive polarity CH HSS influence, mixed with possible
weak influence from the CME that left the Sun on 23 Oct.


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