ARRL

Secure Site Login

News

The K7RA Solar Update

01/08/2021

Tad Cook, K7RA, Seattle, reports: Sunspots disappeared after January 2, so the average daily sunspot number dropped from 27.1 last week to 10 for the December 31 – January 6 reporting week. As a result, average daily solar flux declined as well, from 86.4 to 78.6.

Geomagnetic indicators remain quiet, with planetary A index changing from 6.9 to 5.1, and middle latitude numbers from 5 to 4.

This decline was unexpected, and of course we would rather see more and more sunspots as Solar Cycle 25 progresses, but this is normal. We expect a lot of variability in any sunspot cycle.

Predicted solar flux for the next 30 days looks depressed — far different from the high 80s we saw around Christmas. Solar flux is expected at 74 on January 8 – 15; 80 on January 16; 82 on January 17 – 27; 80 on January 28 – 31, and 78 on February 1 – 6. Flux values may rise to 82 around mid – February.

Planetary A index is predicted at 5 on January 8 – 9; 8 on January 10 – 11; 5 on January 12 – 16; 10 on January 17 – 20; 5 on January 21 – 24; 8 on January 25 – 26; 5 on January 27 – 31; then 10, 10, and 8 on February 1 – 3, and 5 on February 4 – 5. The A index may rise to 10 by mid-February.

This prediction, prepared by the US Air Force, is updated daily, usually after 2120 UTC.

Here’s the geomagnetic activity forecast for January 8 – February 3 from J.K. Janda, OK1HH.

Geomagnetic field will be:

  • quiet on January 10, 12-14, 22, 30-31

  • quiet to unsettled on January 11, 23, 27-29, February 1

  • quiet to active on January 8, 15-16, 21, 24-26

  • unsettled to active January 9, 17, 19-20, February 3

  • active to disturbed January 18, February 2

  • Solar wind will intensify on (January 8-9, 15-17, 19-20,) 21 (- 22, (23, 25-26,) February 2-3

Note: Parentheses mean lower probability of activity enhancement.

The predictability of changes is lower again, as there are ambiguous and changing indications, including rapidly emerging and disappearing narrow bands of solar coronal holes.

Sunspot numbers for December 31 – January 6 were 25, 23, 22, 0, 0, 0, and 0, with a mean of 10. The 10.7-centimeter flux was 81.2, 80.4, 81.5, 80.4, 77.6, 75.1, and 74.1, with a mean of 78.6. Estimated planetary A indices were 3, 4, 2, 2, 3, 11, and 11, with a mean of 5.1. Middle latitude A index was 2, 3, 1, 1, 3, 9, and 9, with a mean of 4.

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out K9LA’s Propagation Page.

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.

Share your reports and observations. 



Back