Subject: Weekly Highlights of Solar and Geomagnetic Activity, 20 - 26 March 2023

:Product: Weekly Highlights and Forecasts
:Issued: 2023 Mar 27 0524 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
20 - 26 March 2023

Solar activity reached moderate levels on 20 March due to an
isolated M1 flare (R1-Minor) at 20/0148 UTC from Region 3256 (S23,
L=010, class/area, Eho/300 on 25 Mar). The large collection of
remaining sunspot regions produced nothing higher than C-class flare
activity throughout the rest of the reporting period.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit reached
moderate levels throughout the reporting period.

On 23-24 March, Earth was impacted by the most significant
geomagnetic storm of the current solar cycle. It began as a Strong
(G3) geomagnetic storm on 23 March at about 1500 UTC and peaked on
24 March at around 0400 UTC as a Severe (G4) geomagnetic storm. This
was the first Severe Geomagnetic Storm since 04 November 2021 (as
reported from Potsdam). The storm was significantly stronger than
expected. On 22 March, the Space Weather Prediction Center (SWPC)
issued G1 and G2 watches for 23 and 24 March respectively. The most
likely source of the geomagnetic storm was a long duration solar
flare on 20 March at 1534 UTC. SWPC and international partner
modeling suggested weak glancing impacts from the 20 March CME.
ENLIL modeling parameters were likely degraded due to the
unavailability of wide angle coronagraph (SOHO/LASCO C3) or STEREO
Ahead imagery. The solar wind environment was significantly
disturbed after the CME arrival. Total field strength peaked at 22
nT. The Bz component reflected prolonged southward deviation of -15
to -17 nT for over 14.5 hours. The remainder of the summary period
observed unsettled to active geomagnetic levels.



Forecast of Solar and Geomagnetic Activity
27 March - 22 April 2023

Solar activity is expected to be at low levels with a slight chance
for (R1-R2, Minor-Moderate) events.

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 27 March - 06 April, with moderate
levels on 07-22 April.

Geomagnetic field activity is expected to reach G1 (Minor) storm
levels on 20-21 April, with active conditions on 31 Mar and 01,
10-11, 16, 18 April in response to recurrent CH HSS influence. Quiet
to unsettled levels are anticipated for the remainder of the outlook
period.


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