Over the past week we saw solar activity decline somewhat. Average daily sunspot number declined from 55.7 (during the January 7-13 period) to 46 during the recent period, January 14-20.

Over the same periods average daily solar flux declined from 106.5 to 100.7. Average daily planetary A index went from 11.1 to 9, and average daily mid-latitude A index declined from 8.4 to 5.6.

Predicted solar flux is 105 on January 22-23, 110 on January 24-28, then 105, 100 and 105 on January 29-31, 110 on February 1-4, 105 on February 5-11, 100 on February 12-14, 95 on February 15-19, and 105 on February 20-25.

Predicted planetary A index is 12 on January 22, 8 on January 23-24, 10 on January 25-26, then 9, 5, 12 and 8 on January 27-30, 5 on January 31 through February 1, then 15, 12 and 8 on February 2-4, 5 on February 5-6, 12 on February 7-8, 10 and 8 on February 9-10, 5 on February 11-17, then 8, 12 and 8 on February 18-20 and 5 on February 21-23.

We saw one new sunspot on January 14, another on January 17, and two more on January 19 and 20. At 0530 UTC on Friday, January 22 I can see four numbered sunspot regions on the sun.

A forecast from OK1MGW predicts quiet to unsettled conditions on January 22, mostly quiet January 23-25, quiet to unsettled January 26, quiet to active January 27, active to disturbed January 28, quiet to unsettled January 29-30, mostly quiet January 31, quiet to unsettled February 1, quiet to active February 2-3, mostly quiet February 4-6, quiet to active February 7-8, quiet to unsettled February 9-10, mostly quiet February 11, quiet February 12-14 and mostly quiet February 15-17.

He expects increases in solar wind on January 27-28, February 1-3 and 7-8.

David Moore sent a link to an article and video titled “Solar Filament Collapses in Stunning New NASA Sun Video.” See it at http://huff.to/1P2xqIR .

Solar activity has been weak, and this chart of solar activity over the past year bears this out: http://www.solen.info/solar/

But we should see some seasonal improvements in HF propagation over the next few months the days become longer and we move toward the spring equinox in the Northern Hemisphere.


For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of the numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and planetary A index are in downloadable spreadsheet format at http://bit.ly/1VOqf9B and http://bit.ly/1DcpaC5.

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 http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins.

Sunspot numbers for January 14 through 20 were 36, 38, 38, 48, 48, 55, and 59, with a mean of 46. 10.7 cm flux was 103.2, 103.5, 99.9, 100.6, 99.9, 97.5, and 100.4, with a mean of 100.7. Estimated planetary A indices were 8, 6, 4, 4, 5, 11, and 25, with a mean of 9. Estimated mid-latitude A indices were 6, 4, 3, 3, 4, 7, and 12, with a mean of 5.6.