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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SB PROP @ ARL $ARLP009
ARLP009 The ARRL Solar Report

ZCZC AP09
QST de W1AW
Propagation Forecast Bulletin 9 ARLP009

From ARRL Headquarters

Newington, CT February 27, 2026
To all radio amateurs

SB PROP ARL ARLP009
ARLP009 The ARRL Solar Report

Spaceweather.com [ http://Spaceweather.com ] for February 27 reports about a minor CME hurling towards Earth.


Solar activity remains at low levels due primarily to C-class flares just beyond the SE limb near S21. The largest was a C5.3 flare on February 25. On the visible disk, an approximate 5-degree filament eruption was observed centered near S08W27 with an associated C2.6 flare.


The eruption was accompanied by a Type II radio sweep (595 km/s) and possibly two related coronal mass ejections (CMEs), first observed in ST A COR2
imagery beginning on February 25. Two CMEs were observed off the NE and E
limbs in the imagery. However, SOHO/LASCO C2 imagery only showed the
northerly CME. Analysis of the CMEs is in progress.


Solar activity is likely to remain at low levels with a slight chance for isolated M-class activity (R1-R2/minor-moderate), as the bright regions currently seen at the east limb rotate onto the visible disk.


Solar wind parameters continued to show Coronal Hole High Speed Stream (CH
HSS) influence. Solar wind speed ranged from 530-650 km/s. Conditions are likely to return to nominal levels as High Speed Stream activity wanes.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, February 26, 2026, by F. K. Janda, OK1HH:


"Between February 22 and 24, there was not a single spot on the solar disk, which last happened less than four years ago. The maximum of the 25th cycle
is behind us, while the years 2024-2025 can be considered the years of cycle maximum.


"At the same time, the Sun is in a key phase of reversing its magnetic field. This process is a natural part of the 11-year solar cycle, usually occurring asymmetrically (the northern and southern hemispheres of the Sun may reverse
at slightly different times, with the process taking several months). The magnetic field in the polar regions of the Sun gradually weakens until it completely breaks down and reforms with the opposite polarity.


"The next eleven-year solar minimum (the transition between the current 25th and future 26th cycles) is expected in 2030-2031, when the Sun's magnetic
field will stabilize again and the star will enter a quiet period. A more precise date for the minimum will only be possible to determine at the end of the decade based on the current development of sunspots.


"During the first week of March, solar activity should gradually increase and then decrease in the following week. Changes in the intensity of the solar
wind will have the greatest impact on the development of shortwave
propagation conditions. For prediction of these changes, it is recommended to monitor the position and area of coronal holes and, in particular, solar
flares that will be located near their edges.


"This can be monitored excellently at www.solarham.com [ https://www.solarham.com/ ] , for example, and even professionals will
confirm that you will find everything you need here to understand the causes
of ongoing events and for operational practice. In addition, we can monitor
the local effects in the ionosphere in detail especially thanks to
ionospheric digisonde stations, dozens of which are available on the
internet!"


Active periods are likely, with a chance for G1 (Minor) storm levels, on February 28 to March 1, due to the anticipated arrival of a CME that left the Sun on February 25.


The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on March 3, and then on March 6 to 8 due to anticipated influence of multiple recurrent coronal holes.


The latest report from Dr. Tamitha Skov, WX6SWW, can be found on YouTube at https://www.youtube.com/watch?v=6SoYfTnrudc [ https://www.youtube.com/watch?v=6SoYfTnrudc ] .


The Predicted Planetary A Index for February 28 to March 6 is 5, 5, 5, 5, 5, 15, and 15, with a mean of 7.9. Predicted Planetary K Index is 2, 2, 2, 2, 2, 4, and 4, with a mean of 2.6. 10.7-centimeter flux is 122, 122, 125, 125,
125, 125, and 130, with a mean of 124.9.


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 ]

NNNN
/EX

ARRL The National Association for Amateur Radio(R)


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