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The K7RA Solar Update

09/25/2020

Tad Cook, K7RA, Seattle, reports: Up until September 23, we saw 32 consecutive days with no sunspots. Then new sunspot group AR2773 appeared, which has a magnetic signature indicating it’s part of new Solar Cycle 25. Spaceweather.com noted it was a weak one, and may not persist for long. The daily sunspot number for September 23 was 13, indicating three sunspots visible in that group, but the sunspot was gone the next day.

Average daily solar flux rose from 69.2 to 71.1 over the September 17 – 23 reporting week. Geomagnetic indicators were about the same, with average daily planetary A index declining from 5.3 to 5.1.

As of September 23, the predicted solar flux for the following 45 days was 73 on September 24 – October 1, and 70 on October 2 – November 2.

The next day that forecast was revised to a predicted solar flux of 70 on every day until November 8. But on Thursday, September 24, the solar flux was 73.6, closely matching the previous day’s forecast.

Predicted planetary A index is 15, 12, 25, and 15 on September 25 – 28; 8 on September 29 – 30; 5 on October 1 – 10; 10 on October 11; 5 on October 12 – 19; 10, 12, 16, 28, 18, and 10 on October 20 – 25; 5 on October 26 – November 6; 10 on November 7;and back to 5 on November 8.

Here’s the geomagnetic activity forecast for September 25 – October 20, from F.K. Janda, OK1HH.

The geomagnetic field will be:

  • quiet on October 6 – 7

  • quiet to unsettled on October 5, 8 – 9, 13 – 16, 18

  • quiet to active on September 30, October 1 – 2, (3 – 4, 10, 12, 17), 19

  • unsettled to active September 25 – 26, 28 – 29, (October 11, 20)

  • active to disturbed (September 27)

  • Solar wind will intensify on September (27 – 28,) 29 – 30, October 1, 13 – 14, (15, 21,) 22

Note: Parentheses mean lower probability of activity enhancement.

The OK1HH forecast sees active to disturbed conditions on September 27, which matches the NOAA and USAF A index prediction of 25 on that date. This disturbance returns about 30 days later with an A index of 28 on October 23.

An interesting article in SciTechDaily discusses, “How NASA & Scientists around the World Track the Solar Cycle.”

Ken, N4SO, on the Alabama Gulf Coast reports that he hears three 15-meter beacons daily on 21.150 MHz — LU4AA in Argentina, OA4B in Peru, and YV5B in Venezuela. These are part of the NCDXF beacon network, and he rarely hears the 1-W transmission. At the other power levels they are S-3 – S-4.

Here’s a recent video from Tamitha Skov, WX6SWW, the “Space Weather Woman.”

Sunspot numbers for September 17 – 23 were 0, 0, 0, 0, 0, 0, and 13, with a mean of 1.9. The 10.7-centimeter flux was 69.7, 69.9, 70.6, 70.2, 71.3, 72.4, and 73.3, with a mean of 71.1. Estimated planetary A indices were 4, 5, 3, 4, 3, 6, and 11, with a mean of 5.1. Middle latitude A index was 5, 4, 4, 4, 3, 5, and 10, with a mean of 5.

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. Monthly charts are no longer be updated on this page. 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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