[SFDX] ARLP024 The ARRL Solar Report

[Bill]

ARLP024 The ARRL Solar Report

	

SB PROP @ ARL $ARLP024

ARLP024 Propagation Forecast

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QST de W1AW

Propagation Forecast Bulletin 24 ARLP024

 From ARRL Headquarters

Newington, CT June 12, 2026

To all radio amateurs

SB PROP ARL ARLP024

ARLP024 The ARRL Solar Report

Solar activity has been at low levels this past week, with most of the 
C-level activity originating from Region 4465, including the largest 
flare of the week, a C2.6 observed on June 10. There are currently 7 
numbered sunspot regions on the disk, with Region 4467 decaying to plage.

There was a Type-II radio sweep detected by the Radio Solar Telescope 
Network (RSTN) on June 10. That radio emission was associated with a 
coronal mass ejection (CME) first observed at the NE quadrant by 
ground-based coronagraph imagery from HAO/MLSO coronagraph late June 10, 
and later by space-based coronagraph LASCO/C2. Modeling indicates there 
is no Earth-directed component.

Other CME activity was observed in the coronagraph imagery later in the 
period, but preliminary analysis indicated no Earth-directed component.

Solar activity is expected to remain at low levels, with a chance for 
M-class flares and a slight chance for X-class flares.

NOAAís SOLAR-1 satellite became operational early on June 11, becoming 
the Space Weather Prediction Centerís primary source of solar wind data. 
Solar wind speeds continued to decrease after the passage of a weak 
transient, reaching 374 km/s at the end of the period. Background solar 
wind conditions are expected through midday June 11, when a coronal hole 
high-speed stream (CH HSS) is anticipated to become geoeffective through 
June 13.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's 
Ionosphere, June 11, 2026, by F. K. Janda, OK1HH:

Overall solar activity is rather low and is expected to continue and 
decline through mid-June. Most active regions are relatively small, 
typically with a simple magnetic configuration. Nevertheless, class C 
flares are occasionally observed, sometimes accompanied by CMEs.

Currently, CMEs from June 9 and 11 are expected to arrive, leading to an 
increase in geomagnetic activity from June 12 to 14. A period of several 
days of calm activity is predicted to begin on June 16.

Shortwave propagation has begun to be significantly affected by the 
sporadic E layer, while its increased activity can be expected to 
continue over the next few days.

The Predicted Planetary A Index for June 13 to June 19 is 6, 6, 8, 8, 5, 
5, and 5 with a mean of 6.1. The Predicted Planetary K Index is 2, 2, 3, 
3, 2, 2, and 2 with a mean of 2.3. 10.7 centimeter flux is 128, 120, 
118, 120, 122, 122, and 125 with a mean of 122.1.

For more information concerning shortwave radio propagation, see 
www.arrl.org/propagation 
<https://arrl.informz.net/z/cjUucD9taT0zNjU0MDEwJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzM1MjA0NQ/index.html> 
and the ARRL Technical Information Service web page at 
www.arrl.org/propagation-of-rf-signals 
<https://arrl.informz.net/z/cjUucD9taT0zNjU0MDEwJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzM1MjA0Ng/index.html>. 
For an explanation of numbers used in this bulletin, see 
www.arrl.org/the-sun-the-earth-the-ionosphere 
<https://arrl.informz.net/z/cjUucD9taT0zNjU0MDEwJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzM1MjA0Nw/index.html>. 
Information and tutorials on propagation can be found at http://k9la.us 
<https://arrl.informz.net/z/cjUucD9taT0zNjU0MDEwJnA9MSZ1PTUyNTQ3MzY2NCZsaT00MzM1MjA0OA/index.html>.


	

	

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