Message:19315 In: PROP.ARL
From: NC8QDate: Sat, 21 Mar 26 09:42:00 Z
Newsgroups: PROP.ARL
Subject: ARLP012 The ARRL Solar Report
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R:260321/0942Z 72083@VE3CGR.#SCON.ON.CAN.NOAM LinBPQ6.0.25
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ZCZC AP12
QST de W1AW
Propagation Forecast Bulletin 12 ARLP012
>From ARRL Headquarters
Newington, CT, March 20, 2026
To all radio amateurs
SB PROP ARL ARLP012
ARLP012 The ARRL Solar Report
Solar activity was at moderate levels following an M2.7 flare from Region 4392 on March 18. This region has shown sporadic grow
th and reorganization in the peripheral spots, but has remained relatively unchanged in its magnetic configuration. New Region
4397 rotated further onto the visible disk and was numbered, yet remained mostly inactive. The remaining regions were relativel
y stable and quiescent.
The M2.7 flare was accompanied by a ten-flare and Type II radio burst with an estimated velocity of 740-860 km/s. An EUV wave i
s visible in GOES SUVI, along with faint field line movement in the NW quadrant.
The associated coronal mass ejection (CME) became visible in SOHO LASCO C2 imagery early on March 18. Analysis indicated a poss
ible arrival at Earth early on March 21. Confidence is fairly low with the fit of this event, due to limited C2/C coronagraph i
magery.
Solar activity is expected to be low on March 21, with a chance for M-class (R1-R2; minor-moderate) level events, due primarily
to the minor instability and variability of Region 4392.
Solar wind parameters reflected near background conditions. Solar wind speed gradually decreased from 450 km/s to end the perio
d at around 380 km/s. The phi angle was predominantly positive. The disturbed solar environment is likely to continue as CME pa
ssage persists into March 20. By March 21, the CME from March 18 is expected to arrive in conjunction with the onset of a negat
ive polarity coronal hole high-speed stream (CH HSS).
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, March 19, 2026, by F. K. Janda, OK1HH:
"Solar activity has been declining over the past two weeks and, despite forecasts that generally predicted an increase, it rema
ins low. Furthermore, there is no reason to expect a significant rise. While increases in geomagnetic activity usually recur ev
ery 27 days (which happened, for example, on March 14), on March 19, for instance, a recurrence of the disturbance from Februar
y 22-23 was expected in vain. This was despite the presence of extensive coronal holes No. 31 and 33 in the center of the solar
disk.
"However, it appears that the geomagnetic disturbance will arrive later. The same applies to the increase in solar activity, wh
ich will also arrive later, but still within the third decade of March. Although it will be smaller than it was during the prev
ious solar rotation. Given the proximity of the equinox, however, both surges will still significantly affect shortwave ionosph
eric propagation."
Unsettled to G1 (Minor) levels are expected on March 22 as the Coronal Mass Ejection and Coronal Hole High Speed Stream effects
persist.
The Predicted Planetary A Index for March 21 to 27 is 35, 25, 15, 15, 18, 10, and 8, with a mean of 16.9. Predicted Planetary K
Index is 5, 5, 4, 4, 5, 3, and 3, with a mean of 4.1. 10.7 centimeter flux is 100, 102, 105, 110, 100, 110, and 120, with a me
an of 106.7.
For more information concerning shortwave radio propagation, see www.arrl.org/propagation and the ARRL Technical Information Se
rvice web page at www.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. Information and tutorials on propagation can be found at http://k9la.us.
Also, check this: "Understanding Solar Indices" from September 2002 QST. https://bit.ly/3Rc8Njt
NNNN
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