Subject: Weekly Highlights of Solar and Geomagnetic Activity, 18 - 24 September 2023

:Product: Weekly Highlights and Forecasts
:Issued: 2023 Sep 25 0237 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
18 - 24 September 2023

Solar activity was at low levels on 18 Sep, moderate levels on 19,
22-24 Sep, and high levels on 20-21 Sep. In total, ten R1 (Minor)
events and two R2 (Moderate) events were registered throughout the
period. Region 3435 (N10, L=102, class/area=Dki/300 on 24 Sep)
produced two M8 flares at 20/1419 UTC and at 21/1254 UTC, along with
four R1 events over 19-22 Sep. CMEs associated with flare activity
on 20-21 Sep were predicted to arrive on 23 Sep, but ultimately
missed. A CME associated with a long-duration M1.2 flare at 22/0336
UTC from Region 3435 resulted in an Earth-directed CME that arrived
on 24 Sep. A CME associated with a filament eruption centered near
N36W05 at 22/0645 UTC was modelled and was predicted to arrive on
24-25 Sep. Region 3443 (N28, L=147, class/area=Dki/260 on 23 Sep)
produced four R1 events on 22 and 24 Sep. A CME associated with
flare activity from Region 3435 at 22/2233 UTC was modelled and is
likely to arrive on 26 Sep.

No proton events were observed at geosynchronous orbit, though a
minor enhancement was observed on 24 Sep.

The greater than 2 MeV electron flux at geosynchronous orbit reached
moderate levels on 18 Sep, and high levels on 19-24 Sep.

Geomagnetic field activity reached G1 (Minor) storm levels on 18 Sep
due to residual effects of a CME from 14 Sep. G3 (Strong) storm
levels were observed on 19 Sep, and active conditions were observed
on 20 Sep, due to the passage of a CME from 16 Sep. Quiet to
unsettled conditions were observed over 21-23 Sep. G2 (Moderate)
storms were observed on 24 Sep due to the arrival of a CME from 22
Sep.

Forecast of Solar and Geomagnetic Activity
25 September - 21 October 2023

Solar activity is expected to be low to moderate with M-class flare
activity likely through much of the period.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to reach high levels on 25-28 Sep, and moderate levels
throughout the remainder of the outlook period.

Geomagnetic field activity is expected to reach G1-G2
(Minor-Moderate) storm levels on 25 Sep due to the passage of a CME
from early on 22 Sep. Active levels are expected on 26 Sep due to
residual CME effects in addition to the predicted glancing-blow
arrival of a CME from late on 22 Sep. Quiet conditions are expected
to prevail throughout the remainder of the period.


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