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The K7RA Solar Update


Average daily sunspot numbers over the past week were up 38.1 points to 75, and average daily solar flux rose 30.7 points to 118.2. Geomagnetic conditions were quiet over the week, with average planetary A index declining from 25.1 to 11, and mid-latitude A index dropping from 17.6 to 9.1.

Predicted solar flux is 125 on October 23-25, 120 on October 26-28, 115 on October 29-30, 85 on October 31 through November 1, 80 on November 2-6, then 85, 90, 95, 100, 105, 110, 115 and 120 on November 7-14, 125 on November 15-17, 120 on November 18-20, and 115 on November 21-22. Flux values then drop to 80 on November 28 through December 3.

Predicted planetary A index is 5, 12, 24 and 8 on October 23-26, then 5, 8, 12 and 10 on October 27-30, 5 on October 31 through November 2, 50 on November 3, 40 on November 4, 25 on November 5, 12 on November 6-7, then 20, 25, 20 and 10 on November 8-11, and 8 on November 12-13. A index then drops to 5 on November 19-24, then bounces back to 50 on November 30.

Those Ap index values of 50 on November 3 and again on November 30 seem to be echoes of the October 7-8 period when planetary A index was 77 and 56. The high values are each spaced one whole solar rotation (27-28 days) from each other.

F.K. Janda, OK1HH, sent us his weekly prediction for geomagnetic conditions. He believes the geomagnetic field will be mostly quiet October 23, quiet to active October 24, quiet to unsettled October 25, quiet on October 26, mostly quiet October 27, quiet to active October 28, mostly quiet October 29, quiet to active October 30 through November 1, active to disturbed November 2, quiet to active November 3, active to disturbed November 4, mostly quiet November 5-6, quiet to unsettled November 7, quiet to active November 8, active to disturbed November 9, quiet to active November 10, mostly quiet November 11-12, quiet to unsettled November 13-14, mostly quiet November 15, quiet to unsettled November 16, and quiet to active November 17.

OK1HH expects increased solar wind on October 29-31, November 2-5, 10-11, 15, 18 and 19-20. The days October 29-30, November 2, 5, 10-11 and 19-20 have a lower probability of increased solar wind.

Now what do all these numbers mean? For good HF conditions we like to see a quiet geomagnetic field, and higher solar flux and sunspot numbers. The A index also represents geomagnetic conditions, and for this, single-digit numbers are desirable, the lower the better. An A index about 10 represents unsettled to active conditions and when it gets toward 50, this is a geomagnetic storm.

The main reason we like low geomagnetic numbers is the higher numbers may indicate higher absorption.

Read for a good explanation of A index and other solar indices.

Dave Ballard, W2VK, and David Moore both sent in a Science Daily article about some large solar storms perhaps being undetected. Read it at .

Ray Price, KE4YOG, of Goldsboro, North Carolina wrote: “Twelve meters has been fun lately. I worked 9K2WA (Kuwait) on 21 October at 1518 UTC along with several other stations. On 22 October at 2145 UTC I worked V73D (Marshall Islands) for an ATNO (All Time New One) on 24.955 MHz. I haven't been able to be on but an hour or two here and there, but 12 meters has been fun.

“All were worked with a Kenwood TS480HX transceiver running 200 W into a 230 Doble up about 60 feet in the sycamore trees.”

The reference to the “230 Doble” had me scratching my head, but I think he may be referring to a 230 foot long doublet. If so, that’s a dipole about 6 wavelengths long on 12 meters.

Don’t forget, this weekend is the SSB portion of the CQ Worldwide DX Contest.  See . Conditions should be good, with no predicted geomagnetic storm until November 3.

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the numbers used in this bulletin, see An archive of past propagation bulletins is at More good information and tutorials on propagation are at

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at and .

Click on “Download this file” to download the archive, and ignore the security warning about file format. Pop-up blockers may suppress the download.

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for October 15 through 21 were 49, 68, 83, 81, 94, 77, and 73, with a mean of 75. 10.7 cm flux was 106.8, 109.1, 116.6, 119.5, 123.7, 122.8, and 129, with a mean of 118.2. Estimated planetary A indices were 10, 8, 11, 22, 5, 9, and 12, with a mean of 11. Estimated mid-latitude A indices were 9, 8, 9, 15, 3, 8, and 12, with a mean of 9.1.




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