| SB PROP @ ARL $ARLP047
ARLP047 Propagation de K7RA
ZCZC AP47
QST de W1AW
Propagation Forecast Bulletin 47 ARLP047
From Tad Cook, K7RA
Seattle, WA December 6, 2024
To all radio amateurs
SB PROP ARL ARLP047
ARLP047 Propagation de K7RA
Solar activity seems to have dropped dramatically from a recent peak. Are we over the cycle peak and headed down again? Too early to say.
Daily average sunspot numbers this week sank to 120.1.
Predicted solar flux is 175 on December 6 to 8, 170 on December 9 and 10, 175 on December 11 and 12, and 205 on December 13 to 17.
Predicted planetary A index is 8 on December 6 and 7, 5 on December 8 to 12, 10, 8 and 5 on December 13 to 15, 8 on December 16 to 18, 12 and 8 on December 19 and 20 and 5 on December 21 through January 6, 2025.
Commentary from OK1HH:
“After the unexpected solar proton flare of 21 November, which took place beyond the Sun’s western limb, a rain of higher-energy protons hit the Earth’s atmosphere. This solar radiation storm had a greater impact at higher latitudes in the southern hemisphere, where it caused a significant increase in attenuation.
“Two days later, two new large sunspot groups appeared near the southeastern limb of the Sun. These produced moderate eruptions daily, which is more or less normal for the 11-year maximum. These are AR3905 and AR3906, which have grown rapidly to a size where they can be observed with the naked eye. There is a relatively small coronal hole near them that could be influencing the solar wind enhancement.
“Following the eruption of a plasma filament near AR3901, a G2 class geomagnetic storm is possible on November 28 and 29, when a CME is expected to impact. However, around 1900 UT on November 28, when this information is written as usual, nothing is still happening. We will see what happens next. It is quite possible that the plasma cloud will only hit the Earth a little and it is also not out of the question that it will miss the Earth completely. So any prediction at this point has a low probability of coming true.”
Send your tips, reports, observations, questions and comments to k7ra@arrl.net. When reporting observations, don’t forget to tell us which mode you were operating.
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.
An archive of past propagation bulletins is at www.arrl.org/w1aw-bulletins-archive-propagation.
More good information and tutorials on propagation are at http://k9la.us.
Also, check “Understanding Solar Indices” from September 2002 QST:
https://bit.ly/3Rc8Njt.
Instructions for starting or ending email subscriptions to ARRL bulletins are at www.arrl.org/bulletins.
Sunspot numbers for November 28 through December 4, 2024 were 149, 162, 103, 83, 113, 126, and 105, with a mean of 120.1. 10.7 cm flux was 213.9, 219.8, 204, 186.3, 185.3, 174.2, and 174.7, with a mean of 202.2. Estimated planetary A indices were 4, 8, 11, 7, 6, 13, and 7, with a mean of 8.3. Middle latitude A Index was 3, 6, 9, 6, 6, 6, 10, and 5, with a mean of 6.
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