ARLP020 The ARRL Solar Report undefined

 

SB PROP @ ARL $ARLP020

ARLP020 Propagation Forecast

 

ZCZC AP20

QST de W1AW

Propagation Forecast Bulletin 20 ARLP020

From ARRL Headquarters

Newington, CT, May 15, 2026

To all radio amateurs

 

SB PROP ARL ARLP020

ARLP020 The ARRL Solar Report

 

Solar activity remained at low levels this past week. Region 4436 was responsible for the majority of the C-flare activity, including the largest flare of the period, a C2.3 that peaked on May 13. Region 4432 rotated off the west limb. Two new regions were numbered during the past 24 hours. Region 4437, which has since decayed to plage, and 4438, resulting in a total of 4 numbered regions now on the visible disk.

 

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

 

Solar activity is expected to remain predominately at low levels with a chance for M-class (R1-R2/minor-moderate) flares through May 16.

 

The solar wind parameters reflected possible combined effects from a coronal hole high-speed stream (CH HSS) influence and a coronal mass ejection (CME) that left the Sun on May 10. The speeds and densities also increased during the period, reaching a maximum speed of 490 km/s, though these had decreased to 450 km/s by the end of the period.

 

Solar wind parameters are expected to remain slightly disturbed through May 14, as the glancing influence of the May 10 CME wanes and a positive polarity CH HSS remains geoeffective. On May 15 - 16, a corotating interaction region (CIR) associated with a negative polarity CH HSS is anticipated to arrive near Earth, likely resulting in more disturbed solar wind conditions.

 

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere, May 14, 2026, by F. K Janda, OK1HH

 

The decline in solar activity during the first two weeks of May was expected and correctly predicted, although it occurred later than during the previous solar rotation. The sunspot groups were small, and the magnetic fields and their configurations were mostly simple. Nevertheless, several solar flares occurred, the largest of which, accompanied by a CME, was observed on May 10 in the northeast of the solar disk. The time of observation (maximum of the event at 1339 UT) corresponds to the occurrence of the Dellinger effect.

 

The distance of active regions on the Sun from coronal holes served as a relatively reliable indicator for predicting geomagnetic activity. This is one reason why the increase on May 13 was predicted with considerable accuracy. The forecast of the subsequent disturbance, expected on May 15ñ17, is supported not only by developments during the previous solar rotation (on April 18ñ21) but also by observations of a CME that could impact Earth.

 

In the last third of the month, an increase in solar activity can be expected without major geomagnetic disturbances, i.e., favorable conditions regarding the state of the ionosphere.

 

The latest solar report from Dr. Tamitha Skov, WX6SWW, can be found on YouTube at

 

The Predicted Planetary A Index for May 16 to May 22 is 20, 18, 15, 5, 5, 8, and 10 with a mean of 11.6. The Predicted Planetary K Index is 5, 5, 4, 2, 2, 3, and 3 with a mean of 3.4. 10.7 centimeter flux is 125, 120, 122, 130, 130, 130, and 120 with a mean of 125.3.

 

For more information concerning shortwave radio propagation, see and the ARRL Technical Information Service web page at . For an explanation of numbers used in this bulletin, see . Information and tutorials on propagation can be found at .

 

Also, check this: "Understanding Solar Indices" from September 2002, QST.

NNNN

/EX

 

 

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