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The K7RA Solar Update

07/24/2020

Tad Cook, K7RA, Seattle, reports: Another Cycle 25 sunspot (AR2767) appeared this week, with a minimum non-zero sunspot number of 11 on July 21 – 23. This puts the average daily sunspot number for the July 16 – 22 reporting week at 3.1, up from 1.7 over the previous 7 days.

Geomagnetic indicators remain very quiet, with average daily planetary A index declining from 5 to 3.9.

This sunspot cycle minimum remains surprisingly inactive. As time goes on, I keep expecting it to perk up, but all indicators remain quiet.

One hopeful outlook for Cycle 25 comes from a group of scientists who predict that it could be one of the biggest solar cycles of all time. Could we finally see a repeat of Cycle 19?

Predicted solar flux — which roughly correlates to sunspot activity — also looks quite dull. Until Thursday, July 23, the 45-day outlook predicted solar flux would never rise hit 70.

Predicted flux values are 70 on July 24 – 31; 69 on August 1; 68 on August 2 – 20; 69 on August 21 – 28, and 68 on August 29 – September 6.

Predicted planetary A index is 8, 12, 8, and 5 on July 24 – 27; 8 on July 28 – 29; 5, 8, and 10 on July 30 – August 1; 5 on August 2 – 18; 8 on August 19 – 20; and 5 on August 21 – September 5.

Spaceweather.com reports a possible coronal mass ejection (CME) impact this week. The faint CME left the sun on July 19 and may cause a minor disturbance on July 24 – 25. This is reflected in the planetary A index forecast.

Here’s the geomagnetic activity forecast for July 24 – Aug 19 from OK1HH. The geomagnetic field will be:

  • Quiet on July 24 – 26; 28 – 29; August 4 – 7, and August 13 – 18.
  • Quiet to unsettled on July 27; 30; August 1 – 3, and August 10 – 12.
  • Quiet to active on July 31; August 8 – 9, and August 19.
  • No unsettled-to-active or active-to-disturbed conditions are expected.
  • Solar wind will intensify on July (23 – 27), August 1 – 3 (– 4, 11 – 15).

Note: Parentheses mean a lower probability of activity enhancement. The predictability of changes remains lower in the long run, as there are very few indications, as the Solar Cycle minimum is here.

Wade Blake, N7LGK, calls attention to this Solar Cycle Progression graph from NOAA.

Last week exceptional HF conditions during the IARU HF World Championship (July 11 – 12) were reported, with no sunspots. K7HV, K7SS, and others reported that conditions on Saturday night were “like the good old days,” with worldwide propagation. 

Sunspot numbers for July 16 – 22 were 0, 0, 0, 0, 0, 11, and 11, with a mean of 3.1. The 10.7-centimeter flux was 68.7, 69, 67.8, 68.9, 69.3, 69.8, and 70, with a mean of 69.1. Estimated planetary A indices were 4, 4, 4, 4, 4, 4, and 3, with a mean of 3.9. Middle latitude A index was 4, 5, 4, 4, 3, 5, and 5, with a mean of 4.3.

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.

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