SB PROP @ ARL $ARLP007
ARLP007 The ARRL Solar Report
ZCZC AP07
QST de W1AW
Propagation Forecast Bulletin 7 ARLP007
From ARRL Headquarters
Newington CT February 28, 2025
To all radio amateurs
SB PROP ARL ARLP007
ARLP007 The ARRL Solar Report
A Coronal Mass Ejection (CME) associated with a filament eruption became
visible on February 26 at 1448 UTC. Model analysis determined this CME to be
a miss ahead of the Sun/Earth line.
Unsettled to active levels are likely on February 28 to March 1 as a Coronal
Hole influence continues, and a glancing blow is possible from a Coronal Mass
Ejection that occurred on February 25.
Solar activity is forecast to range from low to moderate levels through March
22.
Minor to Moderate activity (R1 to R2) is possible at different points
throughout the period as active regions grow, evolve, and return from the
far-side of the Sun. There is a slight chance for R3 (Major) or greater
events if any of the active regions develop additional complex magnetic
structures.
Geomagnetic field activity is expected to be at quiet to unsettled levels
until March 6 with periodic, weak Coronal Hole influences. Unsettled to
active levels, with isolated G1 (Minor) storming conditions are likely from
March 7 to 18 as recurrent negative polarity Coronal Holes are expected to be
in a geoeffective position.
NOAA Space Weather forecasts a 55% chance of a Class-M flare, and a 10%
chance of a Class-X flare, both within the next 48 hours (February 28 to
March 1).
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere -
February 27, 2025, by F. K. Janda, OK1HH:
"Solar activity is now increasing, but the increase is irregular, which
causes, among other things, a decrease in the reliability of forecasts.
Geomagnetically quiet periods, especially when associated with an increase in
total solar activity (such as 20-23 February), are accompanied by improved
conditions for ionospheric radio wave propagation. A subsequent disturbance
can cause even further improvement (which happened on 24 February).
"Following the increase in solar flare activity (from 23 February), two
proton flares were observed on 24 February. In the following days, the
Earth's ionosphere was under the influence of a solar-derived proton rain,
after which the density of free electrons in it decreased due to
recombination.
"However, the worsening of conditions was only noticeable on 25 February. The
very next day, 26 February, there was an improvement, in particular an
increase in the MUF on a global scale. The jump in the solar wind speed also
contributed. However, the changes were so rapid, even within a single day,
that our assessment of the level of conditions could have been reversed,
depending on the time of day and the frequency bands used.
"The developments described can be considered as a harbinger of a March
increase in solar activity. Since the Spring Equinox is approaching, it will
contribute to an improvement in ionospheric shortwave propagation, more
accurately called decameter waves. The possible shorter worse spells on March
1-2 and March 5-6 will make no difference, with the seasonal improvement not
fully manifesting itself until the second half of the month."
This weekend is the ARRL International DX SSB contest. Information can be
found at:
www.arrl.org/arrl-dx [
https://www.arrl.org/arrl-dx?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL] .
For more information concerning shortwave radio propagation, see
www.arrl.org/propagation [
http://www.arrl.org/propagation?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL] and the ARRL Technical Information Service web page at,
www.arrl.org/propagation-of-rf-signals [
http://arrl.org/propagation-of-rf-signals ] . For an explanation of numbers
used in this bulletin, see
www.arrl.org/the-sun-the-earth-the-ionosphere [
http://arrl.org/the-sun-the-earth-the-ionosphere ] . Information and
tutorials on propagation can be found at,
http://k9la.us [
http://k9la.us/ ]
.
Also, check this:
https://bit.ly/3Rc8Njt [
https://bit.ly/3Rc8Njt ] - "Understanding Solar
Indices" from September 2002 QST.
The predicted 10.7 cm flux for February 28 to March 6 is 195, 195, 190, 190,
190, 190, and 185, with a mean of 190.7. The predicted Planetary A Index for
February 28 to March 6 is 12, 10, 8, 5, 5, 5, and 5, with a mean of 7.1. The
predicted K Index for February 28 to March 6 is 4, 3, 3, 2, 2, 2, and 2, with
a mean of 2.6.
NNNN
/EX
ARRL The National Association for Amateur Radio(R)
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ARLP007 The ARRL Solar Report