:Product: Weekly Highlights and Forecasts
:Issued: 2023 May 22 0229 UTC
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# # Weekly Highlights and Forecasts
# Highlights of Solar and Geomagnetic Activity
15 - 21 May 2023

Solar activity varied from low to high levels. Region 3310 (S20,
L=284, class/area=Cko/320 on 19 May) produced the strongest flare of
the period, an M9.6 (R2-Moderate) flare at 16/1643 UTC before it
fully rotated on to the visible disk from the SE limb. Of the 23
M-class flares (R1-R2 Minor-Moderate) recorded during the period,
Region 3311 (N18, L=271, class/area=Ekc/420) was responsible for 21
of them, the largest of which was an M8.9 (R2) flare at 20/1235 UTC.
Although the region was the most magnetically complex of the 18
numbered active regions observed on the visible disk during the
reporting period, it was in a decaying trend by 21 May.

Other activity included Type II radio sweeps at 16/1731 UTC and
17/1522 UTC, two Tenflares on 20 May, and a filament eruption along
side a CME-producing C4.3/Sf flare at 17/1530 UTC from Region 3309
(S18, L=052, class/area=Cro/020). The subsequent CME signatures in
coronagraph were analyzed and modeled with anticipated effects at
Earth suggested late on 21 May.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit was
mostly at background to moderate levels over the reporting period.

Geomagnetic field activity ranged from quiet to G2 (Moderate)
geomagnetic storm levels. Quiet to unsettled levels were observed on
15-16 May and decreased to only quiet levels until of late on 19
May. Active levels were observed during the last synoptic period of
19 May and increased to G2 (Moderate) geomagnetic storm levels early
on 20 May. Total magnetic field strength increased to a peak of 21
nT and Bz reached as far south as -17 nT during what appeared to be
a CIR, with possible embedded transient, ahead of a negative
polarity CH HSS. Bz was persistently southward during the first half
20 May but rotated northward just before midday. With the northward
rotation, geomagnetic activity decreased to unsettled to active
conditions. On 21 May, another enhancement in the solar wind from an
expected CME that left the Sun on 17 May was observed which again
resulted in G2 (Moderate) geomagnetic storm levels through the end
of the reporting period. With the second enhancement, solar wind
speeds increased to between 500-600 km/s and total magnetic field
strength briefly reached 13 nT, while the Bz component was observed
as far south as -10 nt.

Forecast of Solar and Geomagnetic Activity
22 May - 17 June 2023

Solar activity is expected to be at moderate to high, with a chance
for very high, though 30 May, until Region 3311 rotates around the
western limb or decays sufficiently to lower its flare potential.
Low to moderate solar activity is expected for the remainder of the
outlook period.

No proton events are expected at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be high levels from 22 May - 02 Jun in response to
recently elevated geomagnetic activity followed by enhanced solar
wind from coronal hole influence over the next 6 days. Flux levels
are likely to return to moderate levels from 03-17 Jun.

Geomagnetic field activity is expected to range from quiet to G1
(Minor) geomagnetic storm levels. G1 conditions are likely on 22 May
due to persistent transient influence and 23-24 May in response to
negative polarity coronal hole influence. Active conditions are
anticipated on 02 Jun and 16 Jun with unsettled conditions likely on
25-26 May, 03-05 Jun, and 17 Jun due to multiple recurrent coronal
holes. The remainder of the outlook period is likely to be at mostly
quiet levels.