From: "ARRL" <memberlist@arrl.org>

SB PROP @ ARL $ARLP009
ARLP009 The ARRL Solar Report

ZCZC AP09
QST de W1AW
Propagation Forecast Bulletin 9 ARLP009

From ARRL Headquarters

Newington CT March 14, 2025
To all radio amateurs

SB PROP ARL ARLP009
ARLP009 The ARRL Solar Report

Geomagnetic field activity is expected to be at minor storm levels for March 18, and then from March 27 and 27 all due to recurrent Coronal Hole
influences.


Solar activity was at low levels. Multiple C-Class flares were observed from newly numbered Region 4028. More spots are rotating around the Southeast limb that maybe connected to the spot group. The largest flare of the period was a C6.8 on March 13 at 0752 UTC from old Region 4012 that recently rotated
around the Southwest limb.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - March 13, 2025, by F. K. Janda, OK1HH:


"The two geomagnetic disturbances (8-9 March and 12-13 March) were both triggered by an enhanced solar wind blowing from the border between the
coronal holes and the adjacent active sunspot group. OM Kevin VE3EN has
largely restored the content of his website at www.solarham.com [ https://www.solarham.com/ ] , so that we could conveniently observe the
entire solar evolution in the five images at the top of the main page (HMI Intensity, HMI Magnetogram, Coronal Holes, AIA 131, and SUVI 304).


"Again, it is not surprising that both disturbances were correctly predicted, including the expected worsening on the second day of each disturbance (March
9 and March 13).


"Even with thanks to relative simplicity of the situation and the clear
images, it was not surprising that both disturbances were predicted
(including the likely deterioration on the second day of each disturbance, i.e., 9 and 13 March). Both disturbances were followed by only gradual improvement, i.e., a return to normal.


"If solar activity had been higher, the improvement after the disturbances would have been faster. However, there was no large area of spots on the Sun this time, and certainly not any with a more complex configuration of
magnetic fields.


"In the second half of March, solar activity will increase slightly, and the Spring Equinox will occur. While until recently it appeared that the increase in solar activity would be more rapid, even the current expectation of solar flux values only slightly above 200 s.f.u. should result in a noticeable overall improvement, including an increase in MUF at mid-latitudes during the day up to the VHF region."


Spaceweatherlive.com [ https://www.spaceweatherlive.com/ ] contains
informative charts and graphs on Real-time auroral and solar activity.


Slight growth was observed in Regions 4025, 4026, and in the leader spots of 4019. The rest of the spotted regions were either stable or in decay. No Earth-directed CMEs were observed.


Solar activity is expected to be low with a chance for M-class (R1 to R2,
Minor to Moderate) flares on March 13 to 15.


A persistent connection to a negative polarity Coronal Hole is expected to cause unsettled to active levels, with periods of G1 (Minor) storm conditions possible through March 15.


The Space Weather Prediction Center also reports there is an increased chance for M-class flaring (R1-R2, Minor to Moderate) on March 14 to 16. The SWPC predicts that Geomagnetic Activity Probabilities for March 14 to 16 are
calling for 40, 20, and 10% chances of a Minor storm during this reporting period.


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: "Understanding Solar Indices" from September 2002 QST. https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]

The Predicted 10.7 centimeter flux for March 14 to 20 is 160, 170, 175, 180, 180, 185, and 190 with a mean of 177.1. The Predicted Planetary A Index is
15, 8, 8, 15, 20, 8, and 5, with a mean of 11.3. The Predicted Planetary K Index is 4, 3, 3, 4, 5, 3, and 2, with a mean of 3.4.

NNNN
/EX

ARRL The National Association for Amateur Radio(R)
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