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The K7RA Solar Update

03/19/2021

Tad Cook, K7RA, Seattle, reports: Average daily sunspot numbers this week rose just a little, from 18.4 to 19, and average daily solar flux edged up from 78.9 to 78.1. Solar activity remains low.

The vernal equinox, (the first day of spring in the northern hemisphere) occurs at 0937 UTC on Saturday, March 20. That’s when the southern and northern hemispheres will be bathed in approximately equal amounts of solar radiation, which has a positive effect of HF propagation.

On March 17 – 18, the daily sunspot number was only 12 on both days, but the total sunspot area rose from 50 to 200 microhemispheres. Sunspot area was last at this level on February 25. The Space Weather Prediction Center (SWPC) offers daily statistics on daily sunspot area, sunspot numbers, and solar flux.

Average daily planetary A index rose from 7.6 to 10.3, and average daily middle-latitude A index increased from 6.1 to 7.3. Solar wind on March 14 drove the planetary A index to 25, and Alaska’s College A index was 37.

On Wednesday March 17, Spaceweather.com warned that minor geomagnetic unrest was expected on March 18, due to a co-rotating interactive region that would disturb our magnetic field. “CIRs are transition zones between fast and slow-moving solar wind streams. Plasma piles up in these regions, creating shock-like density gradients that often do a good job sparking auroras,” Spaceweather said.

On March 18 Spaceweather.com reported, “NOAA forecasters say that a minor G1-class geomagnetic storm is likely on March 20 – 21 when a stream of high-speed solar wind hits Earth’s magnetic field. The gaseous material is flowing faster than 600 kilometers/second from a southern hole in the sun’s atmosphere.”

The latest forecast from the US Air Force Space Weather Squadron predicts solar flux at 72 on March 19 – 21; 70 on March 22 – 26; 76 on March 27; 76 on March 27; 75 on March 28 – April 1; 78 on April 2 – 3; 70, 74, 76, and 72 on April 4 – 7; 71, 72, and 70 on April 8 – 10; 71, 72, and 71 on April 11 – 13, and 73, 76, 75, and 76 on April 14 – 16. Solar flux is expected to hit a high of 81 on April 19.

Predicted planetary A index is 12, 24, 20, 15, 12, 8, and 10 on March 19 – 25; 5 on March 26 – 27; 25 on March 28; 20 on March 29 – 30; 10, 5, 15, and 8 on March 31 – April 3; 5 on April 4 – 7; 15, 18, 20, and 15 on April 8 – 11; 8, 5, and 8 on April 12 – 14; 20 on April 15 – 16, and 18 on April 17. The A index may peak at 25 again on April 24.

Here is more about the US Air Force and space weather.

This is the geomagnetic activity forecast for March 19– April 13 from F.K. Janda, OK1HH. The geomagnetic field will be:

  • quiet on March (27) April 1, 4, 6, 12

  • quiet to unsettled on March 25 – 26, April 3, 5, 7

  • quiet to active on March 22 – 24, 31, April 13

  • unsettled to active March 21, April 2, 8 – 9, 11

  • active to disturbed March (19 – 20) 28 – 30, April 10

  • Solar wind will intensify on March (19) 20 – 22, (23, 27) 28 – 29, (30 April 1 – 2, (3 – 5, 8,) 9 – 10, (11).

Parentheses indicate lower probability of activity enhancement. Predictability of changes remains very low, as indicators remain ambiguous.

At 2358 UTC on March 17 Australia’s Space Weather Services sent this alert:

“A large southern polar coronal hole with low-latitude extensions will become geoeffective with the CIR possibly arriving from late on March 19 UTC, causing unsettled to active conditions. The HSS from the coronal hole is expected to follow on 20 March UTC, causing active conditions with the possibility of a G1 minor storm. Active conditions are expected to continue on March 21. Aurora may be visible from Tasmania at night on March 19 –20.”

Dave Bono, K6OAK, in Fremont, California reports:

“On Monday, March 15, just before 1900 UTC, 6 and 10 meters were dead, but I noticed a few signals on 12-meter FT8, one being a fairly strong signal from VP8NO in the Falklands. After a few attempts I was able to make contact and received a respectable –10 report. I was running 50 W into a ground-mounted vertical antenna. Not bad for a few minutes in the shack.”

Mike, KA3JAW in Easton, PA (FN20jq) reports 6-meter activity:

“On March 13 at 1627 UTC, 6-meter sporadic-E began to appear on FT8 50.313 MHz with stations from the central states of Illinois, Missouri, Kentucky, Nebraska, Iowa, and Kansas for over 3.5 hours from the first Es cloud formation.

“1659 UTC heard VO1SIX in Newfoundland, Canada (GN27jd), at 1,090 miles coming in from 65° azimuth from a second Es cloud formation.

“1830 UTC Es starts to spread out directly west into the central states of Nebraska, Iowa, and Kansas.

“The farthest distance came from KQ0P (EM19wf) at 1,109 miles, 271° azimuth with a signal of –6 dB, while the radio power output was 15 W using a half-wave dipole at 6 feet above ground.”

The American Geophysical Union (AGU) posted an article, “A 21st Century View of the March 1989 Magnetic Storm,” remembering the Quebec event of 1989.

Arizona TV station KTAR posted “Solar cycle 25 is well underway in 2021 with sunspot action” on its website. It includes some interesting links:

An article on the Brinkwire website, “Solar Activity Reconstructed Over a Millennium – Sun’s Eleven-Year Cycle Traced Back to the Year 969,” takes a historical perspective.

VA7JW offers an overview of the Dominion Radio Astrophysical Observatory at Penticton, which supplies us with solar flux data.

Sunspot numbers for March 11 – 17 were 23, 15, 12, 24, 24, 23, and 12, with a mean of 19. The 10.7-centimeter flux was 78.2, 76.9, 81.1, 78, 74.8, 79.2, and 78.2, with a mean of 78.1. Estimated planetary A indices were 4, 12, 17, 25, 7, 4, and 3, with a mean of 10.3. Middle latitude A index was 3, 9, 13, 17, 5, 2, and 2, with a mean of 7.3.

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.

Instructions for starting or ending email distribution of ARRL bulletins are on the ARRL website.

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