Solar activity has remained at low levels this past week. The largest event of the period was a C3.4 flare originating from Region 4446.
Solar activity has remained at low levels this past week. The largest
event of the period was a C3.4 flare originating from Region 4446.
There are nine numbered regions on the visible disk. Region 4452
showed notable growth and new flux emergence. Region 4450 decayed to
plage, though unassociated transitory pores were observed to its east
and west. Region 4443 decayed into a unipolar spot as it approached
the west limb following the loss of its leading components. Regions
4453, 4454 and 4455 were numbered during the period. Far-side
satellite imagery from Solar Orbiter indicates that Region 4455 is
likely a large bipolar group with its trailing opposite-polarity
spots still located behind the east limb and was numbered proactively
due to its flaring potential. All other regions either continued in
slow decay or remained stable.
A faint, potentially partial-halo, coronal mass ejection (CME) first
seen in LASCO C2 imagery on May 26 and subsequently in GOES/CCOR1 was
analyzed. No obvious on-disk source exists. Modeling suggests a
possible glancing blow at Earth on May 31. Additionally, narrow
eruptions associated with flaring from newly numbered Region 4444
were seen in SUVI imagery but these features are well northward of
the ecliptic plane with no Earth-directed components. No other
Earth-directed coronal mass ejections (CMEs) were observed in
available coronagraph imagery.
Solar activity is expected to be at low to moderate levels through
May 30. There remains a chance for isolated M-class flares
(R1-R2/minor-moderate) driven by the eruptive potential of the
southeast sunspot groups and newly numbered Region 4454.
Solar wind parameters remained slightly elevated and possibly
indicative of weak negative polarity coronal hole high-speed stream
(-CH HSS)influences.
Solar wind speeds varied modestly between 350 and 425 km/s. The phi
angle was predominantly in the negative sector (towards the Sun),
though minor deviations were observed later in the period.
Solar wind parameters are expected to remain mildly enhanced due to
weak coronal high speed stream (-CH HSS) influences through May 29. A
return toward near-background, nominal conditions is anticipated by
May 30.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere, May 28, 2026
Observations of the far side of the Sun by the Solar Orbiter probe
showed us how a new and relatively large active region was
approaching the northeastern limb of the solar disk. But it wasn’t
until it began to emerge on May 28 (designated as AR 4455) that it
became clear the recent rise in solar activity would continue.
Furthermore, the only significant coronal hole in the higher northern
heliographic latitudes is sufficiently far from other active regions,
so we need not expect a significant intensification of the solar
wind.
Therefore, we could expect calmer conditions in the Earth’s
magnetosphere and, at the same time, higher usable frequencies in the
ionosphere for long-distance communications before their seasonal
decline. However, summer in the ionosphere of the Earth’s northern
hemisphere, with higher attenuation in the lower ionosphere during
the long days, will often be enlivened by sporadic E layers in the
mid-latitudes until August.
For more information concerning shortwave radio propagation, see
and the ARRL Technical Information
Service web page at, http://arrl.org/propagation-of-rf-signals. For
an explanation of numbers used in this bulletin, see
. Information and
tutorials on propagation can be found at, .
Also, check this:
https://bit.ly/3Rc8Njt
“Understanding Solar Indices” from September 2002 QST.