Tad Cook, K7RA, Seattle, reports:

On April 12, new sunspot group AR2814 appeared following 5 days of no sunspots at all. Daily sunspot numbers on the following 3 days were 16, 16 and, 17 taking the average daily sunspot number for the April 8 – 14 reporting week to 7, up from 6.4 last week. 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, 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 April 16, due to coronal hole effects.”

Predicted solar flux is 74 on April 15 – 19; 72 on April 20 – 21; 75 on April 22 – May 8, and 72 on May 9 – 17.

Predicted planetary A index is 8, 18, 20, and 16 on April 15 – 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, and 20 on May 14.

Frank Donovan, W3LPL, delivered a presentation on ”HF Ionospheric Propagation” for the Central Arizona DX Association.

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.

 

ARRL News Letter on April 15, 2021