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 favorable¢within the limits of the summer ionosphere in the Earth¡s 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 [ 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)


--- PyGate Linux v1.5.17
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

SB PROP @ ARL $ARLP026
ARLP026 Propagation Forecast

ZCZC AP26
QST de W1AW
Propagation Forecast Bulletin 26 ARLP026

From ARRL Headquarters

Newington, CT June 26, 2026
To all radio amateurs

SB PROP ARL ARLP026
ARLP026 The ARRL Solar Report

Solar activity has remained at low levels, with frequent C-level activity in the SE quadrant of the solar disk. The largest flare of the period was a C3.8 on June 24 from Region 4478, which is the large sunspot that Solar Orbiter
had been tracking across the Sun ¡s far side.


While the majority of the flaring activity this period came from 4478, Region 4475 also produced several small C-flares as additional trailing spots began
to emerge.


Regions 4472 and 4473 continued to decay throughout the period.

Region 4479 was numbered this period. No Earth-directed CMEs were observed in available coronagraph imagery.


Solar activity is expected to continue at predominately low levels on June 25 to 27 with a high chance for M-flares (R1-R2/minor-moderate) and a slight chance for X-flares (R3/strong), primarily due to the potential of Region
4478.


Solar wind parameters were elevated this period from a mix of negative
polarity coronal hole high speed stream (CH HSS) onset and minor magnetic transient influences.


The solar wind speed began the period averaging 350 km/s, then increased sharply on June 24 to ~450 km/s. This was followed by another notable jump in speed, also beginning June 24, ending the reporting period at approximately
600 km/s. Phi was predominantly negative (towards the Sun). Solar wind conditions are expected remain elevated/disturbed through June 27 due to the continued influence of the negative polarity coronal hole high speed stream.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere June 26 by F.K. Janda, OK1HH: After the last and largest sunspot group in the chain as observed by the Solar Orbiter appeared on the southeastern limb of
the solar disk, we can expect another increase in solar activity to a level somewhat higher than expected. At the same time, there are three coronal
holes near the central meridian, with additional active regions just ahead of them.


As a result, the solar wind intensified significantly on June 24, triggering
a geomagnetic disturbance. The maximum southern (i.e., longitudinal)
component of Bz reached -12 nT, whereas this trend appears set to continue through June 27. This will result in highly variable shortwave propagation conditions. Furthermore, propagation will be more affected by the sporadic E layer than in recent days.


The Predicted Planetary A Index for June 27 to July 3 is 8, 5, 5, 5, 5, 5,
and 18 with a mean of 7.3. The Predicted Planetary K Index is 3, 2, 2, 2, 2,
2, and 5 with a mean of 2.6. 10.7 centimeter flux is 130, 130, 132, 135, 145, 138, and 140 with a mean of 135.7.


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)


--- PyGate Linux v1.5.18
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)