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The K7RA Solar Update

12/08/2017

Solar activity declined slightly over the past week, another period which saw multiple days (five) with no sunspots. We will see more of these periods over the next 2-3 years as the sun progresses toward solar minimum.

There was a geomagnetic storm peaking on December 5. In Alaska, the College A index reached 55, and peaked around the middle of the UTC day with K index reaching 7 over two 3-hour readings.

Our reporting week (Thursday through Wednesday) of November 30 through December 6, compared to the previous seven days, we saw average daily sunspot numbers decline from 9.9 to 3.4, and average daily solar flux from 73.5 to 69.6.

Recent consecutive days with zero sunspots were October 8-14, October 16-20, November 1-13, November 19-24, and December 1-5.

You can observe data from periods around the last solar minimum with long consecutive periods of no sunspots at:
ftp://ftp.swpc.noaa.gov/pub/indices/old_indices/2007_DSD.txt , ftp://ftp.swpc.noaa.gov/pub/indices/old_indices/2008_DSD.txt , ftp://ftp.swpc.noaa.gov/pub/indices/old_indices/2009_DSD.txt , and ftp://ftp.swpc.noaa.gov/pub/indices/old_indices/2010_DSD.txt .

Over the past two weeks average planetary A index increased from 6.7 to 11.6 while average mid-latitude A index went from 5 to 8.1.

Predicted solar flux is 68 on December 8-10, 70 on December 11-14, 75 on December 15-16, 74 on December 17, 73 on December 18-20, 74 on December 21-22, then 76, 74, 72, 73 and 72 on December 23-27, 70 on December 28 through January 8, 72 on January 9, 75 on January 10-12, 74 on January 13, 73 on January 14-16, then 74, 74, 76, 74 and 72 on January 17-21.

Predicted planetary A index is 8 on December 8, 5 on December 9-10, 12 on December 11-12, 8 on December 13, 5 on December 14-16, then 8, 25 and 10 on December 17-19, 8 on December 20-21, 5 on December 22-26, 10 and 8 on December 27-28, 5 on December 29-30, then 32, 48, 18, 12 and 8 on December 31 through January 4, 5 on January 5-6, then 12, 15, 12 and 8 on January 7-10, 5 on January 11-12, then 8, 25 and 10 on January 13-15, 8 on January 16-17, and 5 on January 18-21.

F.K. Janda, OK1HH sends us his geomagnetic activity forecast for the period December 8 til January 3, 2017.

“Geomagnetic field will be:
Quiet on December 9, 17, 23-24
Mostly quiet on December 8, 10, 14-16, 22, 25, 30
Quiet to unsettled on December 11, 26, 28
Quiet to active on December 12, 20-21, 27, 29, 31, January 2-3
Active to disturbed on December 13, 18-19, January 1

Amplifications of the solar wind from coronal holes are expected
on December  8 (-11), 17-22, (24-25), 30-31

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


A new sunspot group (AR2690) emerged on December 6 after a period of no sunspots, but spaceweather.com reports that early on December 7 it is already fading.

This weekend is the ARRL 10 meter contest. There is a good chance for sporadic-e propagation. See http://www.arrl.org/10-meter .

Tamitha Skov released this new video on December 7: https://www.youtube.com/watch?v=sgQtC0EOIHI


 
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 November 30 through December 6, 2017 were 11, 0, 0, 0, 0, 0, and 13, with a mean of 3.4. 10.7 cm flux was 71.7, 70.2, 71.5, 69, 68.4, 67.9, and 68.3, with a mean of 69.6. Estimated planetary A indices were 11, 8, 4, 2, 11, 29, and 16, with a mean of 11.6. Estimated mid-latitude A indices were 9, 5, 2, 1, 6, 21, and 13, with a mean of 8.1.

 



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