SB PROP @ ARL $ARLP042
ARLP042 Propagation de K7RA
QST de W1AW
Propagation Forecast Bulletin 42Â ARLP042
From Tad Cook, K7RA
Seattle, WAÂ October 16, 2015
To all radio amateurs
The Australian Space Forecast Centre issued a geomagneticÂ disturbance warning at 2345 UTC on October 15. The alert said “TheÂ continued strengthening of the solar wind stream due to coronal holeÂ effect may lead to isolated periods of minor geomagnetic storms onÂ 16 October.”
Sunspot numbers over the past week (October 8-14) were nearly theÂ same as the previous seven days. Average daily sunspot numbers wentÂ from 37 to 36.9, and average daily solar flux dropped from 93.8 toÂ 87.5
Just as in previous solar cycles, geomagnetic indicators are high asÂ the cycle trends downward after the peak. Go to the bottom of theÂ page at http://www.wm7d.net/hamradio/solar/ and note the graph forÂ Ap (planetary A index) progression. If you look at the graph justÂ above that for solar flux, see how the Ap index is high after theÂ peak of solar flux or sunspot numbers.
From last week to this week, average daily planetary A index wentÂ from 24.3 to 25.1, and average mid-latitude A index moved from 15.7Â to 17.6.
Predicted solar flux is 105 on October 16, 110 on October 17, 120 onÂ October 18-21, 115 on October 22-23, 120 on October 24, 125 onÂ October 25-26, then 130, 120 and 110 on October 27-29, 100, 90 andÂ 85 on October 30 through November 1, 80 on November 2-6, 85 onÂ November 7-8 and 90 on November 9-11. Solar flux then rises to 130Â on November 23 and drops below 100 after November 26.
Predicted planetary A index is 18, 15 and 12 on October 16-18, 8 onÂ October 19-20, 5 on October 21-27, then 8, 12 and 10 on OctoberÂ 28-30, 8 on October 31 through November 2, 20 on November 3, 15 onÂ November 4-5, then 12, 8, 20, 15 and 18 on November 6-10, 20 onÂ November 11-12, 15 on November 13 and 8 on November 14-18.
OK1MGW of the Czech Propagation Interest Group says to expect aÂ quiet to active geomagnetic field on October 16-17, quiet toÂ unsettled on October 18, mostly quiet October 19-20, quiet toÂ unsettled October 21, quiet on October 22-26, mostly quiet OctoberÂ 27, quiet to unsettled October 28-30, quiet to active October 31Â through November 1, active to disturbed November 2-5, quiet toÂ unsettled November 6, quiet to active November 7-9, and quiet toÂ unsettled November 10-11.
David Moore sent this: “The Sun has sprung a leak. A hole in theÂ topmost layer of the Sun and its magnetic field, the size of 50Â Earths, is letting loose an ultra-fast solar wind that has kickedÂ off several nights of auroras down on Earth.” SeeÂ https://shar.es/1uGMJ5 .
Check http://bit.ly/1jGiC66 for a picture of that huge coronal hole.Â Note you can click on the image to zoom in.Â The white linesÂ represent magnetic lines of force. You can check current images ofÂ the Sun at various wavelengths atÂ http://sdowww.lmsal.com/suntoday_v2/ .
If you would like to make a comment or have a tip for our readers,Â email the author at, firstname.lastname@example.org.
- For more information concerning radio propagation, see the ARRLÂ Technical Information Service web page atÂ http://arrl.org/propagation-of-rf-signals.
- For an explanation of theÂ numbers used in this bulletin, seeÂ http://arrl.org/the-sun-the-earth-the-ionosphere.
- An archive of pastÂ propagation bulletins is atÂ http://arrl.org/w1aw-bulletins-archive-propagation.
- More goodÂ information and tutorials on propagation are at http://k9la.us/.
My own archives of the NOAA/USAF daily 45 day forecast for solarÂ flux and planetary A index are in downloadable spreadsheet format atÂ http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .
Click on “Download this file” to download the archive, and ignoreÂ the security warning about file format. Pop-up blockers may suppressÂ the download.
Monthly propagation charts between four USA regions and twelveÂ overseas locations are at http://arrl.org/propagation.
Instructions for starting or ending email distribution of ARRLÂ bulletins are at http://arrl.org/bulletins.
Sunspot numbers for October 8 through 14 were 24, 11, 22, 36, 51,Â 58, and 56, with a mean of 36.9. 10.7 cm flux was 79.7, 81.2, 81.4,Â 84.6, 89.1, 95.6, and 100.7, with a mean of 87.5. EstimatedÂ planetary A indices were 56, 26, 12, 12, 22, 25, and 23, with a meanÂ of 25.1. Estimated mid-latitude A indices were 41, 15, 9, 8, 16, 18,Â and 16, with a mean of 17.6.