venerdì 17 giugno 2022

The K7RA Solar Update

Solar activity increased this week, which we were happy to see, with average daily sunspot number rising from 44.4 last week to 74.3 during this reporting week, June 9-15. Sunspot numbers rose all week, starting at 17 on Thursday, June 9 to 149 on Wednesday, June 15.

Average daily 10.7 cm solar flux increased from 99.4 to 123.9. Solar flux peaked at 145.5 on Tuesday, June 14, but then on Thursday the noon daily reading at the Penticton observatory was 146.7, an increase from 140 the day before. Also on Thursday, daily sunspot number increased from 149 on Wednesday to 159.

The Penticton observatory does three daily readings of solar flux, but it is the local noon reading that is the official solar flux reading of the day, and the one we report here.

You can see the readings at .

The solar flux outlook appears promising for the next few days. The June 16, 2022 forecast from the USAF Space Weather Squadron shows solar flux at 146 on June 17-18, then 144, 140, and 138 on June 19-21, 136 on June 22-24, 100 on June 25 through July 5, then 105, 110 and 115 on July 6-8, 120 on July 9-11, 125 on July 12-16, 120 on July 17-18, 110 on July 19 and 100 on July 20-31.

Predicted planetary A index, a measure of geomagnetic stability, is 8 on June 17-18, 5 on June 19-24, then 10, and 8 on June 25-26, 5 on June 27 through July 7, 8 on July 8-10, then 5, 8, 12, 10 and 8 on July 11-15, then 5 on July 16-19, then 12, 18, 10 and 8 on July 20-23, and 5 through the end of the month.

You can find daily updates for predicted solar flux and A index at . Updates are posted every afternoon, North America time.

F.K. Janda, OK1HH wrote:

"Solar activity grew. The most significant phenomenon was observed in the southeast quadrant of the solar disk - a long-duration (LDE) M3/1n solar flare, observed at 0407 UTC on June 13, accompanied by type-II and IV radio emissions and radio bursts.

"The associated CME was visible off the east. The arrival of the ejected cloud of particles on Earth was calculated to the afternoon of June 15.

"Interplanetary magnetic field strength increased at 0400 UTC on June 15. Solar wind speed was about 500 km/s until shock arrival, when it escalated to 550 km/s and eventually peaked at 624 km/s at 0556 UTC. The geomagnetic field was quiet to active, with an escalation to G1 (Minor) storm levels during the 1200-1500 UTC in reaction to CME effects.

"The MUF increase caused by the storm was registered on June 15 at two intervals, first after 0600 UTC and second before 1200 UTC. In the afternoon to evening a decrease in MUF followed, an increase in the decline and an overall worsening.

"Solar activity will remain elevated for several days, which will help conditions return to above average levels. However, in the Earth's northern hemisphere, sporadic-E layer will cause very irregular development, from increased attenuation to more frequent opening of the shortest shortwave bands."

Here are some solar flare updates:

Thanks to K5EM of the Western Washington DX Club for this study of sporadic-E:

Here is some information about the Maunder Minimum:

Go to and look for an article that appeared June 15-16 titled "Mapping a Magnetic Superstorm."

Look for this fascinating map: .

It purports to show which areas are more vulnerable to effects from geomagnetic storms due to variations in ground and infrastructure conductivity.

Next weekend is ARRL Field Day, a favorite operating activity for many of us. The current outlook shows modest solar flux and perhaps slightly elevated geomagnetic activity. Predicted solar flux for June 24-26 is 136, 100 and 100, with planetary A index at 5, 10 and 8. Field Day starts on Saturday, but it is worth looking at predictions for Friday.

Look for an update in next week's Propagation Forecast Bulletin ARLP025. Field Day rules are at, .

A few days ago, Dr. Tamitha Skov, WX6SWW, posted this:

If you would like to make a comment or have a tip for our readers, please email the author at,

For more information concerning shortwave radio propagation, see and the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see .

An archive of past propagation bulletins is at More good information and tutorials on propagation are at .

Instructions for starting or ending email distribution of ARRL bulletins are at .

Sunspot numbers for June 9 through 15, 2022 were 17, 33, 41, 63, 96,121, and 149, with a mean of 74.3. 10.7 cm flux was 106.4, 110.5, 112.1, 121.3, 131.5, 145.5, and 140, with a mean of 123.9. Estimated planetary A indices were 5, 5, 8, 9, 13, 8, and 20, with a mean of 9.7. Middle latitude A index was 6, 6, 10, 12, 14, 10, and 18, with a mean of 10.9. (