= NOW 18 WPM transition file follows =

After weeks of calm, solar activity is suddenly high again, with two
strong solar flares erupting from opposite sides of the sun. A
Coronal Mass Ejection was associated with a strong solar flare on
May 12, but modeling shows the ejection passing behind Earth. The
geomagnetic field has been at unsettled to active conditions.  A CME
associated with a filament eruption in the northern hemisphere is
expected to pass above Earth on May 17, glancing influences will
likely enhance the solar wind field during this time. The co
rotating interacting region associated with the large, positive
polarity Coronal Hole in the southern hemisphere is expected to
become geoeffective on May 18 which will further enhance the field.
There remains a 65 percent chance that M Class, R1 to R2, Minor to
Moderate, level flare activity will occur through May 18 with a 30
percent chance for X Class, R3 or Strong, levels during the same
time due to the complex magnetic field within Region AR4087.  The
solar wind reflected influences from the Coronal Hole High Speed
Stream originating from the negative polarity coronal hole in the
southwest part of the sun.  Solar activity is expected to be
predominantly low through the outlook period, with varying chances
for M class flare activity.  No proton events are expected at
geosynchronous orbit.  The greater than 2 MeV electron flux at
geosynchronous orbit is expected to be at moderate levels until May
28, and again on June 6 and 7.  High levels are expected from May 29
to June 5 as CH HSS influences increase during this time.
Geomagnetic field activity is anticipated to reach minor storm
levels on May 28 to June 1 under negative polarity CH HSS
influences.  Active levels are likely June 2 and 6.  Mostly
unsettled levels are likely on May 18 to 21, as well as June 2 and
5.  Quiet levels are expected on May 22 to 26.  Weekly Commentary on
the Sun, the Magnetosphere, and the Earths Ionosphere, May 15, 2025,
from F. K. Janda, OK1HH.  The level of solar activity in the first
half of May mostly did not resemble the current peak of the 25th 11
year cycle. The total number of sunspot groups across the disk
ranged from two, on May 2, to six on May 11, with no more than one
larger group.  First the relatively quiet AR4079 and then the
eruptively very active AR4086, whose growth could already be tracked
prior to disk rise.  Ionospheric shortwave propagation conditions
were mostly poor to below average. The main culprit was not the
slightly lower level of solar radiation, but was mainly the solar
wind. The Earths ionosphere was under the influence of elevated free
electron concentrations on most days, while was later bombarded by
protons following the increase in flare activity in AR4086 with
subsequent CMEs.  The consequence was not so much lower MUF values
as increased attenuation and scattering in the ionosphere. This was
all the more advantageous for stations with higher powers and, in
particular, with antenna systems with low radiation angles.  Further
increases in solar activity in the northern half of the solar disk
are still expected in the coming months but cannot be predicted more
accurately. In modern times, however, we can monitor it closely and
prepare for it all the better and in good time.  On May 16,
Spaceweather.com reports that an Aurora warning is issued for the
planet Mars.  The latest solar report from Dr. Tamitha Skov, WX6SWW,
can be found on YouTube.  Links to articles or other websites
mentioned in this bulletin can be found in teleprinter, packet, and
Internet versions of 2025 Propagation Forecast Bulletin ARLP018.
The Predicted Planetary A Index is 5, 8, 10, 8, 8, 6, and 6, with a
mean of 7.3.  The Predicted Planetary K Index is 2, 3, 4, 3, 3, 2,
and 2, with a mean of 2.7.  10.7 centimeter flux is 115, 115, 120,
125, 125, 125, and 130, with a mean of 122.1.

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