During the recent reporting week (December 14-20) the first six days had zero sunspots. On December 20 one new sunspot group appeared (2692) with a sunspot number of 16. The average daily sunspot number decreased from 6.9 during the previous seven days to 2.3.

Average solar flux increased from 71 to 71.5, average planetary A index went from 7.4 to 9.4, and maid-latitude A index increased from 5.5 to 6.1.

Predicted solar flux for the next 45 days is 75 on December 22-28, 74 on December 29 through January 1, 76 on January 2-5, 74 on January 6-13, 72 on January 14-19, 74 on January 20-28, 76 on January 29 through February 1, and 74 on February 2-4.

Predicted planetary A index is 8 on December 22-23, 5 on December 24-26, 10 and 8 on December 27-28, 5 on December 29-30, then 10, 25, 15 and 10 on December 31 through January 3, 5 on January 4-6, then 10, 12 and 8 on January 7-9, 5 on January 10-12, 22 on January 13-14, then 20, 16, 10 and 8 on January 15-18, 5 on January 19-22, 12 and 8 on January 23-24, 5 on January 25-26, then 10, 25, 15 and 10 on January 27-30, 5 on January 31 through February 2, 10 on February 3 and 12 on February 4.

F.K. Janda, OK1HH sent this:

"Geomagnetic activity forecast for the period December 22 to January 17, 2018

Geomagnetic field will be:
Quiet on December 23, 26, January 5-6, 11
Mostly quiet on December 22, 24, 30, January 4, 10, 15
Quiet to unsettled on December 25, January 7, 17
Quiet to active on December 27-29, 31, January 2-3, 8-9, 12, 14, 16
Active to disturbed on January 1, 13

Amplifications of the solar wind from coronal holes are expected on December (24-28,) January 1-3, (6-8,) 10-13

Remark:
- Parenthesis means lower probability of activity enhancement."



Kent Trimble, K9ZTV of Jefferson City, Missouri helpfully pointed out that in last week’s bulletin ARLP049 I wrote JT8 when I should have written FT8. That line should read “FT8 seems to have taken the amateur radio service by storm in recent months, with an amazing rate of acceptance due to its weak signal capabilities and easy implementation.”

Not sure I trust the source, but this article has a number of interesting references: http://bit.ly/2kxhgxN

The article mentions that in 2017 there have been 96 days (27 percent) with no sunspots, but as of this week that number is 101 days, or 28 percent, according to Spaceweather.com. The same list shows that in 2009, 71 percent of the year had no sunspots.

Tamitha Skov posts great videos of her space weather predictions on YouTube, but they are usually after my weekly bulletin is posted. Check for her latest at: https://www.youtube.com/user/SpWxfx

I like the descriptions of space weather phenomena in this article: http://bit.ly/2BQsBAq


For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of 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/.

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 December 14-20, 2017 were 0, 0, 0, 0, 0, 0, and 16, with a mean of 2.3. 10.7 cm flux was 72.1, 71.7, 71.3, 71, 71.6, 68.8, and 74.2, with a mean of 71.5. Estimated planetary A indices were 5, 5, 4, 24, 17, 6, and 5, with a mean of 9.4. Estimated mid-latitude A indices were 2, 3, 3, 16, 12, 4, and 3, with a mean of 6.1.