Subject: Weekly Highlights of Solar and Geomagnetic Activity, 15 - 21 April 2024

:Product: Weekly Highlights and Forecasts
:Issued: 2024 Apr 22 0200 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
15 - 21 April 2024

Solar activity reached moderate levels on 15 Apr, 16-19 Apr and 21
Apr and was at low levels on 20 Apr. A large amount of numbered
regions were recorded on the visible disk, with 26 in total. Region
3639 (N26, L=222, class/area=Eki/320 on 17 Apr) produced the highest
flare of the period, an M4.0/1n (R1-Minor) at 15/1932 UTC. 17 other
M-class (R1) flares were observed this period from multiple other
regions. An complex area of sunspot groups was observed in the
southern hemisphere. Region 3638 (S17, L=226, Cai/beta) was far from
the most magnetically complex of the group but was very active in
its production of eruptions associated with numerous CMEs over the
past week. Most of the ejecta was thought to move south of the
ecliptic but some of the activity may have produced CMEs whose
periphery may be on the Sun-Earth line.

Other activity included an eruption N of Region 3636 (S21, L=251, Class/area=Cso/100 on 13 Apr) around 15/0557 UTC. A faint CME
thought to be associated with the event was observed in SOHO/LASCO
C2 imagery beginning after 15/0648 UTC. Modeling of the CME
suggested arrival on 18 Apr but the most pronounced portion of the
CME was observed passing Earth over 19 Apr.

No proton events were observed at geosynchronous orbit.

The greater than 2 MeV electron flux at geosynchronous orbit ranged
from normal background to moderate levels.

Geomagnetic field activity was ranged from quiet to G3 (Strong)
geomagnetic storm levels this period. Quiet to unsettled conditions
on 15 Apr increased to G1 (Minor) geomagnetic storm levels due to
transient influence from a CME activity on the Sun over 12 Apr.
Quiet to unsettled conditions on 17 Apr were associated with a weak
passing CME that left the Sun on 14 Apr. Quiet conditions were then
observed on 18 Apr as solar wind conditions trended towards nominal
levels. An increase to G3 (Strong) geomagnetic storm conditions were
observed with the passage of CME associated with activity on the Sun
over 15 Apr. Total magnetic field strength (Bt) reached a peak of 18
nT at 19/1425 UTC. The Bz component was sustained in a far southward orientation with a maximum deflection of -17 nT observed at 19/1421
UTC. Solar wind speeds steadily increased from the low 300's to
~500 km/s by the end of 19 Apr. Bt returned to near 5 nT on 20 Apr
and the geomagnetic field responded with quiet to unsettled
conditions. Active conditions were again observed on 21 Apr
following additional periods of sustained Bz south.

Forecast of Solar and Geomagnetic Activity
22 April - 18 May 2024

Solar activity is expected to be moderate levels
(R1-R2/Minor-Moderate), with a chance for X-class flare R3 (Strong),
over 22-27 Apr due to a plethora of productive sunspots rotating
towards the W limb. As those spots groups rotate off, solar activity
is likely to be a low levels with a chance for M-class (R1-R2),
through the remainder of the outlook period due to both developing
spots in the E hemisphere and the return of productive spot groups
on the farside of the Sun.

There is a chance for the greater than 10 MeV proton flux at
geosynchronous orbit to reach above the S1 (Minor) levels over 22-27
Apr due to the plethora of sunspots in the W hemisphere.

The greater than 2 MeV electron flux at geosynchronous orbit may
reach high levels on 22-25 Apr in response to geomagnetic activity
observed on 19 Apr.

Geomagnetic field activity is like to reach active levels over 22-24
Apr and 26-27 Apr in response to multiple coronal hole high speed
streams (CH HSSs). There is potential for combined influence of
coronal hole activity and multiple weak transients over 22-24 Apr.
Unsettled levels are likely on 25 Apr, 01-03 May, and 05-07 May due
to the anticipated return of multiple other weak CH HSSs. The
remainder of the outlook period is likely to be at mostly quiet
levels.


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