From: "ARRL" <memberlist@arrl.org>

SB PROP @ ARL $ARLP002
ARLP002 Propagation de K7RA

ZCZC AP02
QST de W1AW
Propagation Forecast Bulletin 2 ARLP002

From Tad Cook, K7RA

Seattle, WA January 10, 2025
To all radio amateurs

SB PROP ARL ARLP002
ARLP002 Propagation de K7RA

Solar activity was a bit weak during recent days. Average daily sunspot
number was 159.1. During the previous week the average was 194.7.


Predicted solar flux for the near term is 165 on January 10-11, 160 on
January 12, 155 on January 13-17, 200, 210 and 220 on January 18-20, then 230 on January 21-25, then 225, 220, 215, 210, 205 and 200 on January 26-31, 170
on February 1-2, 165 on February 3-4, 170 on February 5-6 and 175 on February 7.


Predicted planetary A index is 8 on January 10-11, then 10 on January 12-13,
5 on January 13-14, then 8 on January 15-16, 10 on January 17-20 and 5 on January 21-30, then 18, 15, 12, 10 and 8 on January 31 through February 4.


Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere - January 9, 2025, from F. K. Janda, OK1HH:


"For most of the eleven-year solar cycle, two numbers are more or less sufficient to give us a rough estimate of the state of the ionosphere and shortwave propagation conditions: the solar activity index (optimally the
solar flux) and the geomagnetic activity index (usually the daily A index or the three-hour K index is sufficient). We need more information during the
high solar activity period and much more at the peak of the high cycle.


"It may not yet be enough to understand what is going on, let alone predict
it. These include the solar wind speed and particle density (free electrons
and especially energetic protons) and the strength and polarity of the longitudinal component of the interplanetary magnetic field. Another
excellent tool is ionospheric probe measurements, especially ionograms.
Unlike the pre-Internet era, we all have access to them.


"Yet, or perhaps because of this, we often experience surprises, whether a
lull or disturbance. The quiet post-Christmas period and the big solar flares on 30 December were followed by geomagnetic disturbances on 1-2 January, accompanied by auroras and SAR, observable even in the mid-latitudes. The following decrease in solar activity and irregular rises in geomagnetic activity (3-7 January) mostly resulted in a deterioration of shortwave conditions. The improvements were mostly brief and occurred irregularly. Moreover, forecasts of further developments were unreliable.


"A further upsurge in solar activity is not expected until the second half of January, after large sunspot groups begin to reappear in the eastern part of solar disk. With few exceptions, major geomagnetic disturbances should follow after the active regions on the Sun reach the central meridian, in February."


"Solar Observances" from the Royal Observatory of Belgium:
https://www.sidc.be [ https://www.sidc.be ]


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 ] .


An archive of past propagation bulletins is at www.arrl.org/w1aw-bulletins-archive-propagation [ http://arrl.org/w1aw-bulletins-archive-propagation ] . More good information and tutorials on propagation are at http://k9la.us [ http://k9la.us/ ] .


Also, check this article: "Understanding Solar Indices" from September 2002 QST.

https://bit.ly/3Rc8Njt [ https://bit.ly/3Rc8Njt ]

Instructions for starting or ending email subscriptions to ARRL bulletins are at www.arrl.org/bulletins [ http://arrl.org/bulletins ] .


Sunspot numbers for January 2 through 8, 2025 were 173, 190, 193, 178, 154, 113, and 113 with a mean of 159.1. 10.7 cm flux was 212.4, 199.9, 209.3,
168.6, 171.9, 167.7,and 160.2 with a mean of 184.3. Planetary A index was 22, 9, 32, 20, 12, 15 and 8 with an average of 16.9. Middle latitude A Index was 14, 7, 21, 12, 13, 8, and 6, with a mean of 11.6.

NNNN
/EX

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