Over the past reporting week (December 15-21) solar activity was little changed from the previous seven days, although on two days (December 16-17) there were no sunspots. Average daily sunspot numbers declined two points from 13 to 11, and average daily solar flux bumped up one point to 73.2.

Average planetary A index changed from 13.3 to 7.9, and average mid-latitude A index from 9 to 5.7.

The outlook for the next month shows daily solar flux in a big downward adjustment for the next week, compared to the forecast in yesterday’s ARRL Letter. The average predicted solar flux Wednesday on December 23-28 was 84.2, but in Thursday’s forecast it dropped suddenly to 62.

Predicted solar flux is 73 on December 23-24, 72 on December 25-29, 77 on December 30-31, 79 on January 1-3, 77 on January 4-5, 75 on January 6-10, 77 on January 11-12, 75 on January 13-14, 73 on January 15-17, 75 on January 18-23, 77 on January 24-27, 79 on January 28-30 and 77 on January 31 and February 1.

Predicted planetary A index is 12 on December 23-24, 8 on December 25, 5 on December 26 through January 1, then 8, 10, 20, 22, 16, 14 and 6 on January 2-8, 5 on January 9-13, 10 on January 14, 15 on January 15-16, 25 and 28 on January 17-18, 12 on January 19-20, 8 on January 21, and 5 on January 22-28.

From Australia’s Space Weather Services:

Subj: SWS Geomagnetic Disturbance Warning 16/57

Issued At 0002 UTC/22 December 2016

By the Australian Space Forecast Centre.

The effect of a high speed solar wind stream from a coronal hole is expected to keep the geomagnetic activity enhanced from 22 to 24 December. Minor storms may be observed throughout this period with the possibility of some major storm periods on 22 and 23 December.

INCREASED GEOMAGNETIC ACTIVITY EXPECTED

DUE TO CORONAL HOLE HIGH SPEED WIND STREAM

FROM 22-24 DECEMBER 2016

GEOMAGNETIC ACTIVITY FORECAST

22 Dec:  Active to minor storm, some major storm periods possible

23 Dec:  Active to minor storm, isolated major storm periods possible

24 Dec:  Unsettled to active, isolated minor storm periods possible

We also have the weekly geomagnetic prediction for December 23 to January 18 from F.K. Janda, OK1HH, of the Czech Propagation Interest Group.

Geomagnetic field will be:

Quiet on December 30-31, January 1, 8-11

Mostly quiet on December 27-28, January 2, 12, 15-16

Quiet to unsettled on January 2-3, 14, 29

Quiet to active on December 23-26, January 4, 6-7, 13, 17

Active to disturbed on January 5, 18

Increases in solar wind from coronal holes are expected on December 23-25, January 3-8, 17-18.

W4KUT’s comments on Cycle 19 in last week’s bulletin drew quite a response.

Jon Jones, N0JK wrote: "Interesting comments from W4KUT regarding solar Cycle 19. I have heard from 6 meter ops who were active during Cycle 19 of daily North America coast to coast F2 contacts on 6 meters with just a few watts on AM and indoor dipoles during the fall and winter months. With the higher F2 MUF, 6 meter contacts also occurred from the Midwest to New England and California via F2.

“International DX was limited due to many countries, particularly in Region 1, not having a 50 MHz allocation. The IGY, however, gave special permission to a few operations from Region 1, so several stations completed WAC on 50 MHz during Cycle 19.

“This was a comment re. cycle 19 in 1957 from the UKSMG regarding 6 meters from Japan: ‘During the peak of Cycle 19, the fall DX season of 1957, North America was coming in every day to Japan (on 50 MHz). At the same time, VE (Canada), KL7 (Alaska), and KH6 (Hawaii) signals were also heard every day. On October 9, 1958 -  JA3CE and CT3AE (Madeira Island) had a QSO establishing the new record via long path for 50 MHz of over 25,000 km.’ (http://www.uksmg.org/content/historyjapan.htm)”

KH6CJJ wrote: "My novice license was issued in 1957.  As a Novice, I was limited to CW with crystal control and had only one or two crystals in the 15-meter novice band. As I remember, one was around 21.175. In the evenings, I would hear VKs and ZLs operating AM around that frequency with great signals. I started calling them on CW and worked many cross mode.  My 60-watt signal was loud enough there to cause them to see who was calling, even though I was many kc away and on CW.

“I got my Conditional (General, for those who did not have access to an FCC examination office) license in 1958. Band conditions were so good that in the Fall and Spring I would cause big pileups of Europeans on 15 while running 40 watts AM with my Heathkit DX-35.  Europe is the toughest place to work from Hawaii and I have never had the same pileups ever since, even running more power on SSB with a better antenna.”

Max White, M0VNG, sent this article about activity at the core of the Sun: http://bit.ly/2ie0EYl

Here is an article from the Chinese Academy of Sciences regarding sunspot helicity, which I had not heard of: http://bit.ly/2i05pG4

Helicity definition: https://www.aa.washington.edu/research/HITsi/research/helicity

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/.

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 15 through 21 were 12, 0, 0, 13, 12, 25, and 15, with a mean of 11. 10.7 cm flux was 72.5, 72.6, 72.1, 72.3, 72.8, 74.9, and 75, with a mean of 73.2. Estimated planetary A indices were 3, 3, 6, 9, 5, 6, and 23, with a mean of 7.9. Estimated mid-latitude A indices were 2, 2, 3, 6, 5, 4, and 18, with a mean of 5.7.