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SB PROP @ ARL $ARLP006
ARLP006 The ARRL Solar Report

ZCZC AP06
QST de W1AW
Propagation Forecast Bulletin 6 ARLP006

From ARRL Headquarters

Newington CT February 21, 2025
To all radio amateurs

SB PROP ARL ARLP006
ARLP006 The ARRL Solar Report

Solar activity is expected to range from low to moderate levels through March 15. There is a varying chance for R1 or R2 (Minor or Moderate) events, and a slight chance for R3 or greater events.


Geomagnetic field activity is likely to reach G1 (Minor) levels on February
28, March 9, and March 12 to 14. Active levels are predicted for March 1. Quiet, and quiet to unsettled conditions are expected to prevail throughout
the remainder of the period.


The NOAA Ap Index Forecast is 5 for February 21 and 22.

The NOAA Space Weather Prediction Center reports no space weather storms predicted for the next 24 hours.


For the last 24 hours, solar flare activity has been at low levels with only
a C-Class observed. The largest flare was a C8.1 on February 19.


This flare was accompanied by a Type II radio emission and associated CME off the Southwest edge of the solar disk. Modelling efforts determined the bulk
of the CME to miss ahead of Earth's orbit. However, a weak glancing influence cannot be ruled out late on February 24.


Region AR3996 is the largest and most complex region on the disk but was responsible for only one C-Class flare. Flux emergence and an increase in interior spots can be seen in Region AR3998 but overall the region has been fairly quiet.


Spaceweather.com [ http://Spaceweather.com ] has an article link from the ''Advancing Earth And Space Sciences'' website concerning an extreme compression of Earth's magnetic field that was caused by the May 2024 solar superstorm.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - February 20, 2025, by F. K. Janda, OK1HH:


''The increase in geomagnetic activity following the decrease in solar
activity is a simple phenomenon to explain: systems of magnetic field lines over active regions in the Sun open up and charged particles (both free electrons and the nuclei of hydrogen atoms, or protons themselves) slip
through them more easily into space.


''In Earth's orbit, we see an increase in the solar wind and, consequently,
an increase in geomagnetic activity. At the same time, the ionization rate of the ionosphere is increasing, while the shortwave propagation conditions may not only worsen (due to scattering on inhomogeneities) but also improve as
the MUF may grow. This was well known, for example, on Saturday 15 February
on the Europe-North America route.


''The only geomagnetically quiet days in the first half of the month were 3-7 February. Then the solar wind, blowing from the long canyon-shaped coronal hole, intensified and geomagnetic activity was elevated for most of the
second third of February. A calm trend can be expected on most days of the
last third of the month. Although there does not appear to be a significant increase in solar activity, it is sufficiently high. In addition, spring is approaching, which is good news for the state of the ionosphere.''


The predicted Planetary A Index is 5 for February 21 to 26, and 10 on
February 27. The predicted Planetary K Index is 2 on February 22 to 26, and 3 on February 27. Predicted 10.7 cm solar flux is 170 for February 22 to 23,
190 on February 24, 195 on February 25, 200 on February 26, and 195 on
February 27.


Sunspot numbers for February 16 to 20, 2025 were 271, 218, 187, 119, and 123, with a mean of 183.6.

NNNN
/EX

ARRL The National Association for Amateur Radio(R)
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