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The K7RA Solar Update


Over the past reporting week (December 7-13) we saw three days with zero sunspots (December 8, 9 and 13). Compared to the previous seven days, average daily sunspot number more than doubled to 6.9 and average daily solar flux increased from 69.6 to 71.

One new sunspot group (2691) emerged on December 10 with one spot, which increased to three over the next two days, but by December 13 it had all disappeared. You can see it at .

According to as of Thursday, December 14 for all of 2017 so far 27-percent of all days have had no visible sunspots. They say the blank sun count for 2016 was 9-percent. They show the count for 2009 at 71-percent.

Current sunspot and solar flux numbers are low enough that coverage for local 75 and 80 meter nets suffers, because they are too low to reflect high angle radiation at 3.5-4 MHz.

Geomagnetic numbers were low, with average planetary A index declining from 11.6 to 7.4, and mid-latitude A index from 8.1 to 5.6.

The latest forecast from USAF and NOAA shows solar flux at 72 on December 15-17, 75 on December 18-21, 74 on December 22-23, 72 on December 24-26, 70 on December 27 through January 5, 72 on January 6-8, 74 on January 9-19, 72 on January 20-22, and 70 on January 23-28.

Predicted planetary A index is 5 on December 15-16, then 12, 20, 18, 10 and 8 on December 17-21, 5 on December 22-26, 12 and 8 on December 27-28, 5 on December 29-30, then 10, 26, 14 and 10 on December 31 through January 3, 5 on January 4-6, then 14, 16, 14 and 8 on January 7-10, 5 on January 11-12, then 8, 25, 10, 8 and 8 on January 13-17, 5 on January 18-22, then 12 and 8 on January 23-24, 5 on January 25-26 and 10 and 26 on January 27-28.

The above predictions are updated daily, usually after 2115-2130 UTC, and are located at .

F.K. Janda, OK1HH sent his geomagnetic activity forecast for the period December 15 to January 10, 2017.

"Geomagnetic field will be:
Quiet on December 23-24, 26, January 5-6,
Mostly quiet on December 16, 25, January 4,
Quiet to unsettled on December 15, 17, 30, January 7-8
Quiet to active on December 20-22, 27-29, 31, January 3, 9
Active to disturbed on December 18-19, January 1-2, 10

Amplifications of the solar wind from coronal holes are expected on December (17,) 18-22, (24-25, 30-31,) January 1-3, (4,)
5-7, (8)

Parenthesis means lower probability of activity enhancement."

A pretty good post about aurora appeared in an adult Scouting blog at . It showed nice images of aurora too, although it is important to keep in mind that the most beautiful and dramatic images are captured using long exposure times.

This post makes a common error when it says, "The Sun cycles in about 11 years of increased sunspots," when actually the period of increased sunspots is somewhere in the middle of this period. Eleven years is the approximate total length of a typical solar cycle, which may vary from 9 to 14 years, from one solar minimum to the next.

English usage nitpick: Instead of "and can hurdle solar particles toward Earth" I think the word the author had in mind was “hurtle”. They sound mostly the same, so are often confused, according to

The post contains a very useful link to a frequently updated forecast of aurora at

Reports from last weekend’s ARRL-10-meter contest indicate terrible conditions. I operated briefly on Saturday, hearing nothing but local area CW signals, no phone.

Checking the ARRL contest soapbox at, it looks like nobody used a dupe sheet or duplicate checking program; activity was so low, they didn’t need one.

KE2SX in North Carolina (FM05sw) commented that he worked only 6 “very local stations” over the whole weekend (all in his state), so there was only a single multiplier--his own state!

K2AF reported from New Jersey (FN20nu) that this is his favorite contest, but "This year, I am hoping that I got both station's calls right so that I don't end up with a negative score."

The latest space weather news from Dr. Tamitha Skov:

FT8 (the latest mode from K1JT) 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. But check out this blog post from NW7US regarding the Olivia mode, which facilitates actual conversations via weak signals:

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good information and tutorials on propagation are at

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 December 7-13, 2017 were 11, 0, 0, 11, 13, 13, and 0, with a mean of 6.9. 10.7 cm flux was 67.9, 69.9, 71.1, 72, 72.3, 71.4, and 72.1, with a mean of 71. Estimated planetary A indices were 10, 5, 4, 3, 10, 13, and 7, with a mean of 7.4. Estimated mid-latitude A indices were 9, 4, 3, 2, 8, 9, and 4, with a mean of 5.6.