Subject: Weekly Highlights of Solar and Geomagnetic Activity, 17 - 23 August 2026

:Product: Weekly Highlights and Forecasts
:Issued: 2026 Aug 24 0259 UTC
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# Weekly Highlights and Forecasts
#
Highlights of Solar and Geomagnetic Activity
17 - 23 August 2026

Solar activity reached moderate levels on 19, 20 and 21 Aug and was
at low levels on 17, 18, 22, and 23 Aug. Region 4513 (N04, L=50,
class/area Ekc/260 on 22 Aug) was the main contributor of M-class
flares, producing four out of the five M-flares observed. The
largest, an M8.1/Sf flare that peaked at 20/1142 UTC, had an
associated Type II radio sweep (estimated speed of 1201 km/s) and a non-Earth-directed CME. Region 4513 also produced an M1.0 flare at
19/1824 UTC, an M1.8/Sf flare at 20/0805 UTC, and an M2.9/Sf flare
at 20/1611 UTC, as well as multiple C-class flares. Region 4507
(N04, L=197, class/area Ehi/300 on 18 Aug) added an M1.6 flare at
21/1017 UTC and multiple C-class flares as well.<o:p></o:p></span>

Although proton levels never reached the S1 (Minor) storm threshold,
the greater than 10 MeV flux levels at geosynchronous orbit were
slightly enhanced between 3-6 pfu on 17-23 Aug. This enhancement was
likely associated with an energetic event from at or just beyond the
western limb on 21 Aug.<o:p></o:p></span>

The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels on 17-20 and 23 Aug, and reached high
levels on 21-22 Aug. <o:p></o:p></span>

Geomagnetic field activity was at quiet to active levels on 17 Aug,
reached G1 (Minor) storm levels on 18-19 Aug, quiet to unsettled on
20-21 Aug, and returned to quiet levels on 22-23 Aug. The elevated
conditions on 17-19 Aug were attributed to the flanking influence
from a CME that left the Sun on 14 Aug, combined with the onset of a
CIR ahead of a negative polarity CH HSS. The slightly elevated
activity continued on 20-21 Aug as influence from the negative
polarity CH HSS persisted, and then decreased by 22-23
Aug.<o:p></o:p></span>

Forecast of Solar and Geomagnetic Activity
24 August - 19 September 2026

Solar activity is expected to be at low levels, with a chance for
M-class flares (R1/R2-Minor/Moderate) and a slight chance for
X-class (R3-Strong) flares on 24 Aug - 03 Sep, mainly attributed to
the flare activity and magnetic complexity of Region 4513. Activity
is then likely to decrease to just a slight chance for M-class
flares (R1/R2-Minor/Moderate) from 04 Sep - 19 Sep.

There is a slight chance for a greater than 10 MeV proton event on
24 Aug - 03 Sep, mainly attributed to the magnetic complexity of
Region 4513. No proton events are expected from 04 Sep - 19 Sep.

The greater than 2 MeV electron flux at geosynchronous orbit is
expected to be at high levels on 24-27 and 30 Aug, and then again on
16-18 Sep. Normal to moderate levels are expected on 28-29 and 31
Aug, and then from 31 Aug- 15 Sep and 19 Sep,

Geomagnetic field activity is expected to be quiet to unsettled
throughout the entire period, with a chance for active conditions 28
Aug, and 13-14 Sep, all attributed to coronal hole high speed stream
influence.


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