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The K7RA Solar Update

04/16/2021

Tad Cook, K7RA, Seattle, reports: On April 12, new sunspot group AR2814 appeared following 5 days of no sunspots. Daily sunspot numbers on the next 4 days were 16, 16, 17, and 22, taking the average daily sunspot number for the April 8-14 reporting week from 6.4 last week to 7. The April 15 sunspot number of 22 was not included in this average. So far in 2021, 39% of the days had no sunspots.

Geomagnetic indicators were quiet, with average daily planetary A index declining slightly from 6.6 to 5.1. Likewise, middle latitude A index changed from 5.6 to 4.1.

On April 14 Spaceweather.com reported a high-speed stream of solar wind from a hole in the sun’s southern hemisphere. This could produce a minor geomagnetic storm on April 17.

At 2338 UTC on April 14 and again at 0239 UTC on April 16, the Australian Space Forecast Centre issued this Geomagnetic Disturbance Warning: Geomagnetic activity is expected to increase to active levels with a chance of an isolated minor storm period from late on April 16, due to coronal hole effects. The April 16 warning said to expect the effects to continue through Sunday, April 18.

Predicted solar flux is 74 on April 16 – 19; 72 on April 20 – 21; 70 on April 22 – 23; 75 on April 24 – May 8; 72 on May 9 – 17, and 75 on May 18 through the end of the month.

Predicted planetary A index is 18, 20, and 16 on April 16 – 18; 12, 8, 5, and 10 on April 19 – 22; 8 on April 23 – 24; 5 on April 25 – 26; 10 and 8 on April 27 – 28; 5 on April 29 – May 3; 15 on May 4; 5 on May 5 – 7; 8 on May 8; 5 on May 9 – 10; 8 on May 11 – 12; 5 on May 13; 20 on May 14; 8 on May 15 – 16, and 5 on May 17 – 18.

Here’s the geomagnetic activity forecast for April 16 – May 11 from F.K. Janda, OK1HH, who has been compiled this weekly bulletin since January 1978.

The geomagnetic field will be:

  • quiet on April 25, May 1-3, 5

  • quiet to unsettled on April 26, 28-30, May 6-11

  • quiet to active on April 19-20, 23-24

  • unsettled to active April 21-22, 27

  • active to disturbed April 16-17, (18,) May 4

  • Solar wind will intensify on April (16-17,) 18-19, (21-22, then irregularly between April 23-May 1,) May 3-5, (6-7, 10-11)

Parentheses means lower probability of activity enhancement.

Jon Jones, N0JK, reported on April 15: Stations in New England spotted CE2SV and CE3SX (FF46) on 50.313 MHz FT8 ~ 2200 UTC on April 13. Likely a sporadic-E link to transequatorial propagation (TEP). AC4TO (EM70) in Florida reported 18 DX contacts in 10 countries on April 13. Solar flux was 83.

Steve Sacco, NN4X reported: Here in Florida, we saw a late-afternoon opening into Europe on both 10 and 12 meters. Looking west on 10 on FT8, I noticed ZL3IO completing a QSO with CT1ENI, and then calling EA5RW. Note that it’s the middle of the night in EU at 2034 UTC.

Don’t miss this truly remarkable presentation on “HF Ionospheric Propagation” by Frank Donovan, W3LPL, to the Central Arizona DX Association

Universe Today has an article on Galileo sunspot drawings and an application of artificial intelligence.

Here is the April 14 report and forecast from Space Weather Woman Tamitha Skov, WX6SWW.

Sunspot numbers for April 8 – 14 were 0, 0, 0, 0, 16, 16, and 17, with a mean of 7. The 10.7 centimeter flux was 74, 77.8, 70.4, 72.9, 82.8, 72.8, and 74.4, with a mean of 75. Estimated planetary A indices were 5, 3, 5, 6, 5, 5, and 7, with a mean of 5.1. Middle latitude A index was 3, 2, 3, 5, 4, 5, and 7, with a mean of 4.1.

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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