Subject: Weekly Highlights of Solar and Geomagnetic Activity, 31 March - 06 April 2025

:Product: Weekly Highlights and Forecasts
:Issued: 2025 Apr 07 0314 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
31 March - 06 April 2025

Solar activity ranged from low to moderate levels. An M5.6 flare on
Tuesday at 0734 UTC from Region 4046 (N10, L=298,
class/area=Cho/0250 on 01 April) was the largest of the week. It was accompanied by a 195 sfu Tenflare and some unremarkable discrete
frequency bursts. No Earth-directed CME was associated with this
event, and in fact, all CME detections throughout the week were
judged to miss Earth. The only other M-flare for the remainder of
the week occurred later that same day at 2231 UTC, an M2.5 from
Region 4048 (S16, L=278, class/area=EKC/0450), the largest active
region on the disk throughout the week. The only other M-flare to
occur earlier in the week, an M1.2 event, happened on 31 March at
1024. This was also from Region 4048, and was associated with an
enhancement in proton flux described in the next paragraph.

Solar particle events more than made up for the lackluster flare
performance. Proton flux had been rising, most likely in response to
an X1.1 flare that had occurred late last week (see PRF 2578). The
10 MeV protons crossed the 10 pfu threshold briefly on 31 Mar at
1105 UTC before falling below at 1115 UTC. This bump was possibly
related to the M1.2 event described earlier. There was only a brief
respite, however, because the flux again crossed the 10 pfu
threshold at 1430 UTC, peaked on 01 Apr at 0425 UTC (147 pfu), and
ended on 02 Apr at 0910 UTC. Proton flux was above the 100 pfu
threshold on 01 April, from 0205 UTC to 0910 UTC. Note: In the 10
MeV proton event summary, the start time was recorded as 31/1105 UTC
despite the subsequent 3 hours below the 10 pfu threshold.

The greater than 2 MeV electron flux at geosynchronous orbit was
high on 31 Mar-01 April before falling to moderate levels on 2-4
April. A fast solar wind stream became geoeffective on 04 April and
drove flux back to high levels on 05-07 April.

Geomagnetic field activity was at quiet to active levels to begin
the week, with an isolated minor storm period on 03 Apr attributed
to a solar sector boundary crossing. By 04 Apr, conditions had
increased to minor storm levels with the arrival of a negative
polarity coronal hole and fast wind stream. Activity peaked at
moderate storm levels (Kp=6m) during the first synoptic period of 05
April. Conditions remained at disturbed, ranging from unsettled to
minor storm levels, through the first period of 06 April. Once the
fast stream became established, conditions decreased to active to
unsettled levels which persisted through the end of the week.

Forecast of Solar and Geomagnetic Activity
07 April - 03 May 2025

Solar activity is expected to be low for the first nine days of the
forecast period; 11 regions are wil exit the visible disk, with only
4 regions expected to return during the same period. The declining
trend in solar flux and activity is expected to bottom out around 15
April, after which a slowly increasing period is expected. The
anticipated return on 22 April of the active longitudes that gave
rise to Region 4046 (responsible for X-flare activity) should bring
solar activity to moderate and occasionally high levels through the
end of the forecast period.

No proton events are expected at geosynchronous orbit until the
expected increase in flare activity beginning on 22 April. Then
there will be an increasing chance for an isolated proton event as
the more potent regions approach the west limb by the end of the
forecast period.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to begin the forecast period at high levels in response to
the fast solar wind stream. Flux will subside to moderate levels
after 12 April as effects from the fast stream wane. 19 April is
expected to bring a return to high levels, again in response to
another recurrent fast stream. The elevated conditions are expected
to remain through 28 April before returning to moderate levels.

Geomagnetic field activity is expected to be primarily quit to
unsettled, with an isolated active period, until the return of a
recurrent geoeffective coronal hole between 19-21 April. Active
condistions are expected to prevail through 24 April before the fast
solar wind stream wanes. Another recurrent hole is expected to
arrive aorund 01 May, bringing minor storm conditions with the
threat of an isolated moderate storm period.


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