Register Account

Login Help


The K7RA Solar Update


ARLP020 Propagation de K7RA  

QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA Seattle, WA  May 31, 2024
To all radio amateurs   

ARLP020 Propagation de K7RA  
Solar activity was quiet this week. Average daily sunspot number slipped from 155.1 to 124.6, and average solar flux from 198.9 to 164.8.  

Geomagnetic conditions were quiet, with average planetary A index going from 13.9 to 7.9, and middle latitude A index from 11.7 to 9.

Eight new sunspot groups emerged, one on May 23, two on May 25, four on May 26, and one on May 28.

The outlook for the next month predicts solar flux at 175 on May 31 through June 6, then 210, 200, 195, 190, 185 and 180 on June 7-12, 170 on June 13-14, 165 on June 15, 190 on June 16-17, 185 on June 18, then 190 on June 19-20, then 185, 195 and 200 on June 21-23, then 210, 210 and 215 on June 24-26, 225 on June 27-29, 220 on June 30 through July 1, 210 on July 2-4, then 200, 195 and 190 on July 5-7.

Predicted planetary A index is 25 on May 31 and June 1, 5 on June 2-7, then 10, 12, 8, 12 and 10 on June 8-12, 5 on June 13-19 then 15 and 12 on June 20-21, then 5, 12, 8 and 5 on June 22-25, and 5, 10, 12, 12 and 8 on June 26-30, then 5 on July 1-4, then 10, 12, 8, 12 and 10 on July 5-9.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere from OK1HH.

"Over the past seven days, two active regions have returned to the solar disk where large solar flares with CMEs were observed during the last solar revolution. These were regions AR3663 and AR3664, now designated AR3691 and AR3697. The activity of the latter caused a major geomagnetic storm with auroras on 10 May, the largest in decades. Until these large groups of spots reach the center of the solar disk or near the central meridian (i.e., approximately June 6-7), solar activity will increase in a roughly 20-day fluctuation and then decrease again.

"Even the last major solar flare on May 29 afternoon UTC was observed in AR3697 and was accompanied by a CME. Part of the particle cloud will probably hit Earth sometime between late afternoon on June 1 and the morning of June 2. The onset of the phenomenon should be accompanied by an improvement in shortwave propagation conditions and a deterioration can be expected during its continuation on June 2.

"In the following days, due to increasing solar activity and a calmer state of the Earth's magnetosphere, shortwave propagation should improve again. However, if another large solar flare occurs, the development could be much more dramatic. Another reason for the current instability of shortwave conditions is the rise in Summer sporadic-E layer activity in the northern hemisphere. reports NOAA forecasters say a G2 class geomagnetic storm is possible on May 31 when a CME grazes earth. But a NASA forecast suggests a near miss. This is from a CME at 1433 UTC on May 29 from sunspot group AR3664.

More on sunspot group AR3664:

The latest video from Dr. Tamitha Skov, WX6SWW:  

Send your tips, reports, observations, questions and comments to When reporting observations, don't forget to tell us which mode you were operating.

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

An archive of past propagation bulletins is at

More good information and tutorials on propagation are at .  

Also, check this QST article about Solar Indices:  

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for May 23 through 29 2024 were 130, 100, 106, 148, 116, 141, and 131, with a mean of 124.6. 10.7 cm flux was 176.2, 162.8, 152.4, 155.6, 170, 166.4, and 170.5, with a mean of 164.8. Estimated planetary A indices were 10, 9, 6, 10, 8, 6, and 6, with a mean of 7.9. Middle latitude A index was 10, 11, 6, 10, 9, 7, and 10, with a mean of 8.




Instragram     Facebook     Twitter     YouTube     LinkedIn