Subject: Weekly Highlights of Solar and Geomagnetic Activity, 28 August - 03 September 2023

:Product: Weekly Highlights and Forecasts
:Issued: 2023 Sep 04 0549 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
28 August - 03 September 2023

Solar activity ranged from low to high levels. Low levels were
observed on 28-31 Aug. Moderate levels occurred on 01 Sep due to a
long duration M1.2 flare (R1/Minor) at 01/0351 UTC with associated
Type II (743 km/s) and Type IV radio sweeps as well as a 190 sfu
Tenflare. Moderate levels also occurred on 02 Sep due to an M3.3/Sf
at 02/0712 UTC. Solar activity increased to high levels on 03 Sep
due to an M1.1 at 03/0023 UTC and an M6.0 (R2/Moderate) at 03/0836
UTC. All flares were from Region 3413 (N11, L=100, class/area
Dki/400 on 25 Aug). Other activity included a filament eruption
centered near N22W14 beginning at 30/2015 UTC. An associated
partial-halo CME was observed at 30/2200 UTC in SOHO/LASCO C2
imagery. Modelling of this CME showed a potential arrival late on 02
Sep to early on 03 Sep. Another CME associated with the
aforementioned M1.2 flare on 01 Sep was modelled with the potential
for a glancing impact on 05 Sep.

A greater than 10 MeV proton event was observed associated with the
M1.2 flare on 01 Sep. The event reached the 10 pfu (S1/Minor)
threshold at 01/0430 UTC, reached a maximum flux of 25.8 pfu at
01/0610 UTC, and ended at 01/2010 UTC.

The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels.

Geomagnetic field activity ranged from quiet to G2 (Moderate)
levels. Nominal solar wind conditions prevailed through
approximately 31/1630 UTC when an increase in total field to 12 nT
was observed as well as an increase in speed from 323 to 400 km/s. A
further increase in solar wind speed to near 540 km/s happened after
01/1755 UTC, followed by a decrease in solar wind speed beginning
after 02/2125 UTC. Total field ranged from 5-10 nT during this time
with prolonged periods of southward Bz. This was likely the result
of a combination of positive polarity coronal hole high speed stream
(CH HSS) activity and the arrival of the 30 Aug CME. The geomagnetic
field responded with quiet conditions on 28-31 Aug, quiet to
unsettled conditions on 01 Sep, unsettled to G1 (Minor) storming on
02 Sep, and quiet to G2 (Moderate) storming on 03 Sep.

Forecast of Solar and Geomagnetic Activity
04 September - 30 September 2023

Solar activity is expected to be at low levels on 04-14 Sep and
again on 29-30 Sep. There is a chance for M-class flaring (R1-R2/Minor-Moderate) on 15-28 Sep with the return of Region 3413
to the visible disk.

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 04-10 Sep due to CH HSS influence.

Geomagnetic field activity is expected to be at unsettled to active
levels on 04-08 Sep, 14-18 Sep, 23 Sep, and on 28-30 Sep due to CH
HSS activity. There is a chance for a glancing blow from the 01 Sep
CME to impact the geomagnetic field on 05 Sep.


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