Fwd: ARLP025 The ARRL Solar Report
Bill Bode
Begin forwarded message:
From: ARRL <membe...@arrl.org>
Date: June 23, 2026 at 9:03:23 AM EDT
To: bod...@gmail.com
Subject: ARLP025 The ARRL Solar Report
Reply-To: membe...@arrl.org
SB PROP @ ARL $ARLP025
ARLP025 Propagation Forecast
ZCZC AP25
QST de W1AW
Propagation Forecast Bulletin 25 ARLP025
From ARRL Headquarters
Newington, CT June 19, 2026
To all radio amateurs
SB PROP ARL ARLP025
ARLP025 The ARRL Solar Report
Solar activity has been low with only C-class solar flare activity. Region 4465 underwent some decay and only produced a low-level C-class flare. Region 4469 decayed further and was inactive. Region 4470 underwent some growth, but did not increase in magnetic complexity and was primarily inactive. The largest solar flare of the period, a C2.5 on June 17, came from just beyond the west limb with the likely source being recently rotated out-of-view Region 4464.
A coronal mass ejection (CME) became visible in STEREO coronagraph imagery on June 17 and Compact Coronagraph (CCOR) imagery approximately 30 minutes later. This eruption was first determined to be far-sided due to SUVI 304 and 193 imagery; however, the backfilling of a SOHO LASCO data gap prompted a re-analysis and it has since concluded that there may be an Earth-directed component. Modeling is currently ongoing.
There was an additional, faster, eruption off the east limb close to the equator, with the resulting CME first appearing in LASCO C2 imagery on June 17. Due to its faintness, this CME is not visible in other coronagraphs. Modeling of this event is also ongoing, but a significant Earth-directed component is not anticipated.
Solar activity is likely to continue at low levels through June 20, with a slight chance for M-class (R1-minor) solar flares due primarily to the combined flare probabilities of Regions 4465 and 4470.
Solar wind parameters were indicative of a weak disturbance in the interplanetary magnetic field (IMF), which was probably related to anticipated early-stage coronal hole high speed stream (CH HSS) influences. The phi angle was quite variable between sectors. Solar wind speed increased from 400 km/s to nearly 500 km/s before declining to about 450 km/s. Mild solar wind disturbances and enhancements are anticipated through June 20 due to weak positive polarity CH HSS effects.
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere June 19 by F. K. Janda OK1HH:
The low solar activity observed during the second decade of June will be replaced by significantly higher activity in the third decade, as the active regions observed by the Solar Orbiter on the far side of the Sun will gradually emerge.
Geomagnetic activity will generally be relatively low, and shortwave propagation conditions will be relatively favorableówithin the limits of the summer ionosphere in the Earthís northern hemisphere, that is.
And, as was the case in the second third of June, we can expect a significant influence from the sporadic E layer.
The Predicted Planetary A Index for June 20 to June 26 is 10, 5, 8, 12, 5, 5, and 5 with a mean of 7.1. The Predicted Planetary K Index is 3, 2, 3, 4, 2, 2, and 2 with a mean of 2.6. 10.7 centimeter flux is 132, 130, 112, 135, 136, 138, and 140 with a mean of 131.9.
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
ARRL The National Association for Amateur Radio®
