From Newsgroup: rec.radio.amateur.space
:Product: Weekly Highlights and Forecasts
:Issued: 2026 May 18 0431 UTC
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity
11 - 17 May 2026
Solar activity reached moderate levels on 16 May due to four M-class
flares. The largest were an M1.9/2N (R1-Minor) at 16/1612UTC from
Region 4436 (N18, L=330, class/area=Dao/200 on 11 May) and a second
M1.9 flare (R1-Moderate) at 16/1742UTC from Region 4435 (N22, L=040, class/area=Dao/070 on 15 May). The 1612UTC M1.9 was associated with
a Type IV radio sweep, two 10.7 cm radio bursts, and a filament
eruption that was centered at approximately N21W07, which lead to a
complex CME signature in coronagraph imagery. The first front was
first seen in LASCO C2 imagery at 16/1636UTC, and the second front
became visible at approximately 16/1700 UTC. Analysis and modeling
of the event suggests potential for a glancing blow at Earth by mid
UTC-day on 18 May, with the bulk of the material passing northward
of Earth's orbit.
The other two M-flares, an M1.4 at 17/0339UTC and an M1.3 at
16/1629, were also from Regions 4435 and 4436, with the M1.3
following on the heels of the 16/1612UTC M1.9. The other 11 numbered
active regions on this visible disk were either quiet or only
produced C-class activity during the past week. 3 Type II radio
sweeps and an additional 10.7cm radio burst were observed during the
summary period, but they were not associated with any Earth-directed
activity
No proton events were observed at geosynchronous orbit.
The greater than 2 MeV electron flux at geosynchronous orbit was at
normal to moderate levels for the majority of the summary period,
before increasing to high levels at 16/1740UTC. During the summary
period, the maximum value reached was 6,120 pfu at 17/1740UTC.
Geomagnetic field activity reached G1-G2 (Minor-Moderate)
geomagnetic storming levels on 15-16 May due to a negative polarity
coronal hole high speed stream becoming geoeffective late on 15 May.
Total magnetic field strength, Bt, increased all throughout 15 May,
from approximately 3 nT to a peak of 17 nT at 15/1555UTC. The
north-south component, Bz, rotated between +/- 11 nT, with maximum
southward deflections of approximately -13 nT. The interplanetary
magnetic field had returned to background levels by the end of 16
May. A smaller positive polarity coronal hole high speed stream
became geoeffective on 13 May with a max Bt of 13 nT and maximum Bz
southward deflection of -9 nT; however this only produced unsettled
geomagnetic conditions and no NOAA Geomagnetic Storming thresholds
were reached.
Forecast of Solar and Geomagnetic Activity
18 May - 13 June 2026
Solar activity is expected to be at low to moderate levels
throughout the outlook period, with M-class activity (R1-R2,
Minor-Moderate) ranging from a chance to likely and X-class activity
(R3, Strong) ranging from a slight chance to a chance, due to the
flare potential of several active regions currently on the visible
disk and those both expected to return and indicated by Solar
Orbiter magnetic imagery.
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 18 May and 21-23 May due to
influence from the current negative polarity coronal hole high speed
stream and an anticipated solar sector boundary cross on 21 May. The
remaining days of the outlook period are likely to be at normal to
moderate levels.
Geomagnetic field activity is expected to reach G1 (Minor)
geomagnetic storming levels over 18-19 May due to potential
influences from the CME that left the Sun on 16 May arriving in the
near-Earth environment in the midst of the current high speed
stream. The remainder of the outlook period is anticipated to be at
largely quiet to unsettled levels.
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