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The K7RA Solar Update


Tad Cook, K7RA, Seattle, reports: Sunspots disappeared December 8 – 11. Average daily sunspot numbers and solar flux hardly changed at all, with sunspots at 24.4 during the December 9 – 15 reporting week, compared to 24.6 last week, and average daily solar flux shifting from 82.6 to 82.9, rising to 102.5 by Wednesday. But, sunspots have come back dramatically over the past few days, with the daily sunspot number hitting 127 on December 16, when the noon 10.7-centimeter solar flux reading at Canada’s Dominion Radio Astrophysical Observatory (DRAO) was 117.9, reaching 121.5 at the 2200 UTC reading.

Geomagnetic activity was quiet. Average daily planetary A index changed from 7.6 to 5, and average daily middle latitude A index from 5.3 to 3.9.

One new sunspot group emerged on December 12, with two more appearing the next day, two more on December 15, and another two on December 16.

Predicted solar flux over the next month looks very good for this week at 118 on December 17 – 21; 115 and 110 on December 22 – 23; 82 on December 24 – 27; 80 on December 28; 78 on December 29 – January 3; then 80 on January 4 – 10; 82 on January 11, and 84 on January 12 – 17. Predicted flux values drop below 80 after January 24.

Predicted planetary A index is 8 on December 17; 5 on December 18 – 19; 8, 16, 12, and 8 on December 20 – 23; 5 on December 24 – 26; 15, 18, and 12 on December 27 – 29; 8 on December 30 – January 1; 5 on January 2 – 8; 8 and 5 on January 9 – 10; 12, 10, 10, and 8 on January 11 – 14; 5 on January 15 – 22; then 15, 18, and 12 on January 23 – 25, and 8 on January 26 – 28.

Unfortunately, propagation was poor during the annual ARRL 10-Meter Contest over the December 11 – 12 weekend — not surprising with no sunspots on the 2 days prior to the contest, and none over the weekend. On Friday night, I heard no signals (with a modest dipole antenna), so I called CQ on CW just above 28 MHz, and worked one station only 8 miles away. I worked a few stations on Sunday across North America, and heard many trans-equatorial propagation (TEP) signals from South America.

Don’t miss “Understanding an Ionosonde to Understand the Ionosphere,” by propagation expert Eric Nichols, KL7AJ, in the January 2022 edition of QST, currently available to ARRL members online.

Here’s the “Weekly Commentary on the Sun, the Magnetosphere, and the Earth’s Ionosphere” from F.K. Janda, OK1HH.

Solar activity has risen a little more and faster in recent days than we expected. After several smaller eruptions, the probability of an M-class solar flare increased. Although Solar Cycle 25 is still close to minimum, we can expect its maximum in 3 to 4 years to be higher than usually predicted. The last rise in solar activity is not long (in recent days only); after that, a decline can be expected again in the last week of December.

Although most of the active areas are located south of the solar equator and not too far from the coronal holes, we still expect only a slight increase in geomagnetic activity starting the third week of December.

Earth’s ionosphere reacted significantly to the last rise of solar radiation by the rise of MUF. However, the hitherto stable development will be replaced by fluctuations and deformations of the daily course. This will happen probably at the beginning of the third week of December. This will be followed by a relatively significant decrease in MUF, both day and night. The decline of MUF by night will be significant, if the onset of the increase in geomagnetic activity will be up during the night.

Here’s the geomagnetic activity forecast for December 17-23 from Tomas Bayer at The National Geomagnetic Observatory near Budkov in the Czech Republic.

  • Quiet: December 17 – 18, 22 – 23

  • Unsettled: December 18 – 22

  • Active: December 18 – 19

  • Minor storm: unlikely about December 19

  • Major storm: 0

  • Severe storm: 0

Toward the end of current forecast period, we expect, at most, quiet to unsettled conditions.

Max White, M0VNG, noted this article, “Swarm and Cluster get to the bottom of geomagnetic storms,” from the European Space Agency.

Space Weather Woman Tamitha Skov, WX6SWW, has posted more of her continuing space weather course.

I received many emails correcting the information I provided last week regarding the Fred Fish award. This sums it up best.

Sunspot numbers for December 9 – 15 were 0, 0, 0, 12, 40, 40, and 79, with a mean of 24.4. The 10.7-centimeter solar flux was 76.7, 75.7, 76.2, 79.9, 80.6, 88.9, and 102.5, with a mean of 82.9. Estimated planetary A indices were 3, 4, 5, 3, 6, 5, and 9, with a mean of 5. Middle latitude A index was 2, 2, 3, 2, 6, 4, and 8, with a mean of 3.9.

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check this propagation page by Carl Luetzelschwab, K9LA.

A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.

Instructions for starting or ending email distribution of ARRL bulletins are on the ARRL website.

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