SB PROP @ ARL $ARLP024
ARLP024 The ARRL Solar Report

ZCZC AP24
QST de W1AW
Propagation Forecast Bulletin 24 ARLP024

From ARRL Headquarters

Newington CT June 27, 2025
To all radio amateurs

SB PROP ARL ARLP024
ARLP024 The ARRL Solar Report

Solar activity has been at low levels for the past 48 hours, with low-level C-class flares.


There was a narrow coronal mass ejection (CME), likely associated with minor flaring from Regions AR4117 and AR4118 between 1439 UTC and 1524 UTC on June 24. Initial modeling indicated a miss, south and behind Earth's orbit.
However, it should be noted that analysis of this event is low confidence
given the assumed source location.


An enhanced solar wind environment is expected to continue through June 28 under a negative polarity Coronal Hole High-Speed Stream regime before beginning to trend towards a more nominal environment on 29 June.


There is a chance for R1-R2 (Minor-Moderate) events through June 29. There is also a slight chance for an R3 (Strong) or greater event through June 29, as well as a slight chance for S1 (Minor) solar radiation storm conditions
through the reporting period.


Geomagnetic field activity is likely to reach active levels on July 1 to 3,
05 and 6, and 11 and 12, all due to recurrent CH HSS influences. Quiet, and quiet to unsettled conditions are expected to prevail throughout the
remainder of the period through July 19.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - June 26, 2025, by F. K. Janda, OK1HH:


"The last significant solar flare was recorded on June 15, reaching an X-ray brightness of M8.4, while ejecting a CME into space. The particle cloud
arrived at Earth on June 18, with the subsequent increase in solar wind
speed, which caused an improvement in propagation conditions in the lower shortwave bands.


"Although eruptions with higher X-ray brightness were also recorded, they
only caused shorter attenuation in the lower layers of the ionosphere on the illuminated part of the Earth.


"Overall solar activity declined steadily after June 15, with five to six visible sunspot groups. At most two were capable of producing larger
eruptions. Their proximity to two of the three observable coronal holes near the equator made it possible to predict an intensification of the solar wind and the occurrence of geomagnetic disturbances for June 25-26 (or possibly
also June 27).


"This was all the more likely given that it was the central meridian region. Since then, however, the sunspot groups and coronal holes have shrunk. The increase in solar wind speed (up to 700 km/s) and geomagnetic activity (only G1) was therefore smaller. However, the flux of electrons with energies above
2 MeV reached high values, with a maximum flux of 1,260 pfu at 25/1355 UTC.


"Unfortunately, an increase in the concentration of free electrons in the Earth's ionosphere is a relatively common phenomenon this year and worsens
the conditions for shortwave propagation.


"A return to background levels is expected from June 28. In July, larger sunspot groups will return to the solar disk. Therefore, the solar flux will rise slightly during the first ten days. Only a very slight improvement in shortwave propagation conditions can be expected in the summer ionosphere of the Earth's northern hemisphere."


For more information concerning shortwave radio propagation, see www.arrl.org/propagation [ http://www.arrl.org/propagation?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] and the ARRL Technical Information Service web page at www.arrl.org/propagation-of-rf-signals [ http://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 [ http://arrl.org/the-sun-the-earth-the-ionosphere ] . Information and
tutorials on propagation can be found at http://k9la.us [ http://k9la.us/ ] .


Also, check this: "Understanding Solar Indices" from September 2002 QST. https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]

The Predicted Planetary A Index for June 28 to July 4 is 15, 10, 5, 15, 15,
12, and 5, with a mean of 11. Predicted Planetary K Index is 3,3, 2, 4, 4, 4, and 2, with a mean of 3.1. 10.7 centimeter flux is 140, 145, 145, 140, 140, 140, and 145, with a mean of 142.1.

NNNN
/EX

ARRL The National Association for Amateur Radio(R)
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SB PROP @ ARL $ARLP024
ARLP024 Propagation Forecast

ZCZC AP24
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.


NOAA¡s SOLAR-1 satellite became operational early on June 11, becoming the Space Weather Prediction Center¡s 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 [ http://www.arrl.org/propagation?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] and the ARRL Technical Information Service web page at www.arrl.org/propagation-of-rf-signals [ http://www.arrl.org/propagation-of-rf-signals?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . For an explanation of numbers used in this bulletin, see www.arrl.org/the-sun-the-earth-the-ionosphere [ http://www.arrl.org/the-sun-the-earth-the-ionosphere?utm_source=Informz&utm_medium=Email&utm_campaign=ARRL
] . Information and tutorials on propagation can be found at http://k9la.us [ http://k9la.us ] .


Also, check this: "Understanding Solar Indices" from September 2002 QST. https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]

NNNN
/EX

ARRL The National Association for Amateur Radio(R)


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