SB PROP @ ARL $ARLP011 ARLP011 The ARRL Solar Report ZCZC AP11 QST de W1AW Propagation Forecast Bulletin 11 ARLP011 From ARRL Headquarters Newington, CT, March 13, 2026 To all radio amateurs SB PROP ARL ARLP011 ARLP011 The ARRL Solar Report Solar activity was very low to low. Only low-level C-class activity was observed from Regions 4384 and 4389. Slight growth was observed in Regions 4384 and 4391. New Region 4392 was numbered. The rest of the spot groups were either stable or in decay. No Earth-directed CMEs were observed. Solar activity is expected to be at low levels, with a slight chance for M-class (R1-R2/minor-moderate) flares, through March 14. Solar wind parameters were enhanced through March 11. Solar wind speed ranged from approximately 480 to 570 km/s during this time, but decreased to around 400-460 km/s through the rest of the period. High Speed Stream activity persists through March 14. Elevated probabilities are related to the flare potential of both currently observed spot groups as well as the potential from returning regions. No proton events are expected at geosynchronous orbit. The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at high levels from March 16 to 19, and then on March 23 to 30 due to the influence of multiple, recurrent, Coronal Hole High Speed Streams. The remainder of the outlook period is likely to be at normal to moderate levels. Geomagnetic field activity is expected to reach G1 (Minor) geomagnetic storm levels on March 14, 22, and 25 during the onset of a CH HSS. G2 (Moderate) geomagnetic storm levels are likely on March 21 due to negative polarity CH HSS effects. Unsettled to active levels are likely on March 15 to 20, 23, and 24, and on March 256 to 28. 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 latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on YouTube at https://www.youtube.com/watch?v=c9gloRUmKAI. The Predicted Planetary A Index for March 14 to 20 is 20, 15, 10, 10, 10, 12, and 15, with a mean of 13.1. The Predicted Planetary K Index is 5, 4, 3, 3, 3, 4, and 4, with a mean of 4.1. 10.7 centimeter flux is 110, 110, 110, 110, 110, 105, and 110, with a mean of 109.3. For more information concerning shortwave radio propagation, see www.arrl.org/propagation and the ARRL Technical Information Service 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 /EX | 
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