Solar activity remained at low levels this past week. Region 4436 was
responsible for the majority of the C-flare activity, including the
largest flare of the period, a C2.3 that peaked on May 13. Region
4432 rotated off the west limb. Two new regions were numbered during
the past 24 hours. Region 4437, which has since decayed to plage, and
4438, resulting in a total of 4 numbered regions now on the visible
disk.
No Earth-directed CMEs were observed in available coronagraph
imagery.
Solar activity is expected to remain predominately at low levels with
a chance for M-class (R1-R2/minor-moderate) flares through May 16.
The solar wind parameters reflected possible combined effects from a
coronal hole high speed stream (CH HSS) influence and a coronal mass
ejection (CME) that left the Sun on May 10. The speeds and densities
also showed enhancements during the period, with maximum speeds of
490 km/s, through these had decreased to 450 km/s by the end of the
period.
Solar wind parameters are expected to continue to be slightly
disturbed through May 14, as the glancing influence from the May 10
CME wanes and a positive polarity CH HSS remains geoeffective. On May
15 – 16, a corotating interaction region (CIR) associated with a
negative polarity CH HSS is anticipated to arrive near Earth, likely
resulting in more disturbed solar wind conditions.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s
Ionosphere, May 14, 2026 by F. K Janda, OK1HH
The decline in solar activity during the first two weeks of May was
expected and correctly predicted, although it occurred later than
during the previous solar rotation. The sunspot groups were small and
the magnetic field and their configurations was mostly simple.
Nevertheless, several solar flares occurred, the largest of which,
accompanied by a CME, was observed on May 10 in the northeast of the
solar disk. The time of observation (maximum of the event at 1339 UT)
corresponds to the occurrence of the Dellinger effect.
The distance of active regions on the Sun from coronal holes served
as relatively reliable indicators for predicting geomagnetic
activity. This is one reason why its increase on May 13 was predicted
with considerable accuracy. The forecast of the subsequent
disturbance, expected on May 15–17, is supported not only by
developments during the previous solar rotation (on April 18–21) but
also by observations of a CME that could impact Earth.
In the last third of the month, an increase in solar activity can be
expected without major geomagnetic disturbances, i.e., favorable
conditions regarding the state of the ionosphere.
The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found
on YouTube at https://www.youtube.com/watch?v=qLnkogEGx5A
The Predicted Planetary A Index for May 16 to May 22 is 20, 18, 15,
5, 5, 8, and 10 with a mean of 11.6. The Predicted Planetary K Index
is 5, 5, 4, 2, 2, 3, and 3 with a mean of 3.4. 10.7 centimeter flux
is 125, 120, 122, 130, 130, 130, and 120 with a mean of 125.3.
For more information concerning shortwave radio propagation, see
http://www.arrl.org/propagation 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
http://arrl.org/the-sun-the-earth-the-ionosphere . Information and
tutorials on propagation can be found at, http://k9la.us/ .
Also, check this:
https://bit.ly/3Rc8Njt
“Understanding Solar Indices” from September 2002 QST.