Subject: Weekly Highlights of Solar and Geomagnetic Activity, 05 - 11 October 2026

:Product: Weekly Highlights and Forecasts
:Issued: 2026 Oct 12 0344 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
05 - 11 October 2026

Solar activity was at very low to (R1-R2 - Minor-Moderate) levels
throughout the summary period. Region 4545 (N17, L=222, class/area
Dso/070 on 08 Oct) produced an impulsive M1.0 (R1 - Minor) flare at
05/1848 UTC. Region 4547 (N15, L=274, class/area Cri/030 on 06 Oct)
produced an M1.3 flare at 09/1409 UTC as the region exited the west
limb. The majority of the activity was observed from Region 4549
(N10, L=216, class/area Eki/260 on 09 Oct). During the period, the
region produced 39 C-class, 3 R1-Minor, and 2 R2-Moderate flares. It
produced an M6.7/2b flare at 08/1548 UTC with an associated Type II
Sweep with an estimated velocity of 4,125 km/s and a Type IV Sweep.
At 10/1510 UTC, this region produced an M6.4/1n flare with an
associated Type II Sweep with an estimated velocity of 929 km/s and
a 240 sfu Tenflare. The largest region on the disk, Region 4551
(S15, L=102, class/area Eko/400 on 11 Oct) produced 3 C-class
flares. In total, 50 C-class and 7 M-class events were observed.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit reached
high levels on 05-08 Oct and 10 Oct with a peak of 11,300 pfu
observed at 08/1250 UTC. Normal to moderate levels were observed on
09 and 11 Oct.

Geomagnetic field activity ranged from quiet to G3-Strong levels
during the period. Quiet to G1-Minor levels were observed on 05 Oct
and quiet to unsettled levels were observed on 06 Oct, all due to
influences from a positive polarity CH HSS. Mostly quiet levels were
observed on 07-08 Oct. Activity increased on 09 Oct when unsettled
to active levels were observed due to weak influence from a 06 Oct
CME. Activity levels increased further on 10 Oct when unsettled to
G3-Strong levels were observed due to continued influence from CME
activity observed on 06 and 07 Oct. During this level of high
activity, total magnetic field strength increased to a peak of 45 nT
at about 10/1500 UTC and Bz observed some southward deflections to
30 nT at about 10/1630 UTC. Solar wind speeds rapidly increased from
about 380 km/s at 10/1500 UTC to a peak of about 890 km/s at 10/1755
UTC. Associated with this CME activity was some influence from a
negative polarity CH HSS.

Forecast of Solar and Geomagnetic Activity
12 October - 07 November 2026

Solar activity is likely to continue at very low to low levels with
isolated R1-Minor levels possible throughout the period.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at high levels on 14-15 Oct, 23-28 Oct, and 01-04
Nov, all due to anticipated influence from multiple, recurrent CH
HSSs.

Geomagnetic field activity is expected to be reach G1-Minor
geomagnetic storm levels on 13 and 31 Oct , and 01 Nov. Active
levels are likely on 12, 22, and 23 Oct. Unsettled levels are likely
on 14-15, 21, and 24 Oct and 02 and 06-07 Nov. All increases in
goemagnetic activity are associated with anticipated influence from
multiple, recurrent, coronal hole HSSs. The remainder of the outlook
period is likely to be at mostly quiet levels.


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