SB PROP @ ARL $ARLP010
ARLP010 The ARRL Solar Report

ZCZC AP10
QST de W1AW
Propagation Forecast Bulletin 10 ARLP010

From ARRL Headquarters

Newington CT March 21, 2025
To all radio amateurs

SB PROP ARL ARLP010
ARLP010 The ARRL Solar Report

Solar activity reached moderate levels due to an isolated M1.5/1n flare on March 19 at 2040 UTC from Region AR4031. Regions AR4028, AR4034, and AR4035 exhibited slight growth.


Region AR4026 re-emerged in the Southwest quadrant. Regions in the Northwest quadrant, including AR4020, AR4022, AR4025, and AR4031 all appeared to be in
a decay phase.


No Earth-directed CMEs were detected in available coronagraph imagery.

No S1 (Minor) or greater solar radiation storms are expected through March
23.


No significant active region activity favorable for radiation storm
production is forecast.


C-class flares are expected to continue to March 22, with a chance for
isolated M-class (R1-Minor) flares.


A chance for R1-R2 (Minor to Moderate) radio blackouts due to M-class flares will persist through March 23.


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


"While the current solar activity is a bit lower than we would like and then would be consistent with the current phase of the solar cycle, it may be a prelude to another peak within the current 11-year cycle maximum.


"This hypothesis is supported by the starting shift of the sunspot activity from the southern hemisphere of the Sun to the northern hemisphere (see also the M-class flares in AR4031 and the following filament flare, i.e., in the northwest quadrant of the solar disc).


"At the same time, the presently forecasted period is likely to begin with a transient decrease in geomagnetic activity. But this may be interrupted as early as March 23 if an enhanced solar wind blowing from Solar Coronal Hole
24 hits Earth.


"If this happens in the daytime, a so-called positive phase of the
disturbance could follow with an increase in MUF and a general improvement in ionospheric shortwave propagation conditions."


Spaceweather.com [ http://Spaceweather.com ] has a link to an article that discusses new evidence that cosmic rays spark lightning.


Weak disturbances in the solar wind are anticipated through March 20 in response to persistent transient/High-Speed Stream (HSS) effects as well as possible flanking influences of a nearby CME passage that departed the Sun on March 17. Solar wind parameters are expected to slowly diminish on March 21. Another enhancement is expected late on March 22 due to the arrival of a CIR preceding a negative polarity Coronal Hole HSS.


A CIR - or Corotating Interaction Region - is a recurring plasma structure in the heliosphere formed when fast solar wind streams interact with slower
solar wind ahead of them.


Quiet to unsettled levels are expected on March 21. By late on March 22, unsettled to active levels are likely due to the aforementioned CIR arrival.


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 21 to 27 is 195, 200, 195, 190, 180, 165, and 160, with a mean of for a mean of 183.6. The Predicted
Planetary A Index is 8, 5, 5, 5, 15, 25, and 25, with a mean of 12.6. The Predicted Planetary K Index is 3, 2, 2, 2, 4, 5, and 5, with a mean of 3.3.

NNNN
/EX

ARRL The National Association for Amateur Radio(R)
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SB PROP @ ARL $ARLP010
ARLP010 The ARRL Solar Report

ZCZC AP10
QST de W1AW
Propagation Forecast Bulletin 10 ARLP010

From ARRL Headquarters

Newington, CT March 6, 2026
To all radio amateurs

SB PROP ARL ARLP010
ARLP010 The ARRL Solar Report

Solar activity continued at low levels with isolated C-class flaring. Regions 4381 and 4384 remained the primary drivers of activity. The largest event of the period was a C2.9 flare from Region 4381 on March 3. Region 4384
continues to rotate further onto the disk, but foreshortening still hinders a definitive characterization of its magnetic complexity. Region 4378 showed
some new flux emergence but remained mostly inactive.


Region 4383 simplified into a unipolar group following the loss of its
trailing spots, while Region 4380 decayed to plage. No Earth-directed coronal mass ejections (CMEs) were observed in available coronagraph imagery.


Solar activity is expected to be at low levels, with a chance for isolated M-class activity (R1-R2/minor-moderate) through March 6.


A brief description of Sunspots can be found on the Space Weather Prediction Center website at www.swpc.noaa.gov/phenomena/sunspotssolar-cycle [ https://www.swpc.noaa.gov/phenomena/sunspotssolar-cycle ] .


Solar wind parameters reflected the onset of a positive polarity coronal hole high-speed stream (+CH HSS). Solar wind speed increased to 450 km/s. Solar
wind parameters are expected to remain enhanced due to the ongoing influence
of the +CH HSS. Residual enhancements are likely to persist, keeping
conditions slightly above background levels before another enhancement is expected with the onset of a negative polarity coronal hole high-speed stream (-CH HSS). Active conditions are expected on March 7 and 8 as high-speed
stream influences continue.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, March 5, 2026, by F. K. Janda, OK1HH:


"Overall solar activity declined, with the number of sunspot groups ranging between three and six over the past week. Their magnetic configuration was simple, so no significant flares on the solar disk were observed.


"However, the solar flux remained at a relatively high level of 130-148
s.f.u., which, together with a decrease in geomagnetic activity (no major disturbances, just alternating calm and moderately active days), resulted in improved conditions for shortwave propagation.


"The current trend is expected to continue for the time being. A change will
be caused by a decline in solar activity in the second decade of March. This will be very noticeable in the decline in solar radio flux."


The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on March 8, 11, and 12, and March 15 to 19 due to
anticipated influence from multiple, recurrent, CH HSSs. The remainder of the outlook period is likely to be at normal to moderate levels.


Geomagnetic field activity is expected to range from quiet to G2 (Moderate) geomagnetic storm levels. Active conditions are likely on March 10, 12, March 14 and 15, and March 20. Unsettled conditions are likely on March 8 and 9, March 11, March 13, and March 16 to 19. All elevated levels of geomagnetic activity are associated with the anticipated influence of multiple,
recurrent, CH HSSs. The remainder of the outlook period is likely to be at mostly quiet levels.


The current solar 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 March 7 to 13 is 5, 8, 10, 18, 10, 15,
and 10, with a mean of 10.9. Predicted Planetary K Index is 2, 3, 3, 4, 3, 4, and 3, with a mean of 3.1. 10.7-centimeter flux is 156, 156, 150, 145, 140, 135, and 128, with a mean of 144.3.


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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