ARLP012 Propagation de K7RA

Propagation Forecast Bulletin 12 ARLP012 From Tad Cook, K7RA Seattle, WA March 19, 2021 To all radio amateurs

ARLP012 Propagation de K7RA

Average daily sunspot numbers this week rose just a little, from 18.4 to 19, and average daily solar flux changed from 78.9 to 78.1. Solar activity remains low.

Note the vernal equinox, (the first day of spring in the Northern Hemisphere) occurs at 0937 UTC on Saturday, March 20. Both 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 and 18, the daily sunspot number was only 12 on both days, but the total sunspot area rose from 50 to 200 micro-hemispheres. Sunspot area was last at this level on February 25. You can see daily sunspot area along with sunspot numbers and solar flux at .

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 warned that minor geomagnetic unrest is expected on March 18, due to a co-rotating interactive region that will 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.”

On March 18 reported, “NOAA forecasters say that a minor G1-class geomagnetic storm is likely on March 20 and 21 when a stream of high-speed solar wind hits Earth’s magnetic field. The gaseous material is flowing faster than 600 km/s 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 to 21, 70 on March 22 to 26, 76 on March 27, 75 on March 28 through April 1, 78 on April 2 and 3, then 70, 74, 76 and 72 on April 4 to 7, 71, 72 and 70 on April 8 to 10, 71, 72 and 71 on April 11 to 13, then 73, 76, 75 and 76 on April 14 to 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 to 25, 5 on March 26 to 27, 25 on March 28, 20 on March 29 to 30, then 10, 5, 15 and 8 on March 31 through April 3, 5 on April 4 to 7, then 15, 18, 20, and 15 on April 8 to 11, then 8, 5 and 8 on April 12 to 14, and 20 on April 15 and 16 and 18 on April 17. The A index may peak at 25 again on April 24.

More about the Air Force and space weather:

Geomagnetic activity forecast for the period March 19 to April 13, 2021 from F. K. Janda, OK1HH.

“Geomagnetic field will be Quiet on: March (27,) April 1, 4, 6, 12 Quiet to unsettled on: March 25 and 26, April 3, 5, 7 Quiet to active on: March 22 to 24, 31, April 13 Unsettled to active: March 21, April 2, 8 and 9, 11 Active to disturbed: March (19 and 20,) 28 to 30, April 10

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

Parenthesis means 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 UT day 19 March, causing unsettled to active conditions. The HSS from the coronal hole is expected to follow on UT day 20 March, causing active conditions with the possibility of a G1 minor storm. Active conditions are expected to continue on 21 March, Auroras may be visible from Tasmania at night on 19-20 March.”

Dave Bono, K6OAK in Fremont, California reports:

“On Monday March 15th just before 1900 UTC 6 and 10 meters were dead, but I noticed a few signals on 12M 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 watts into a ground mounted vertical antenna. Not bad for a few minutes in the shack.”

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

On March 13 at 1627 UTC six meter sporadic-e began to appear on FT8 50.313 MHz with stations from the central states of IL, MO, KY, NE, IA and KS for over 3.5 hours from the first Es cloud formation.

1659 UTC heard VO1SIX in Newfoundland, Canada (GN27jd) at 1090 miles coming in from 065 degrees azimuth from a second Es cloud formation.

1830 UTC Es starts to spread out directly west into the central states of NE, IA and KS.

The farthest distance came from KQ0P (EM19wf) at 1109 miles, 271 degrees azimuth with a signal of -6 dB while the radio power output was 15 watts using a half wave dipole at 6 feet above ground.

Remembering the 1989 Quebec event:

This article on solar activity has some interesting links:

Historic sunspot activity going way, way back:

VA7JW gives an overview of the Dominion Radio Astrophysical Observatory at Penticton which supplies us with solar flux data:

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 March 11 through 17, 2021 were 23, 15, 12, 24, 24, 23, and 12, with a mean of 19. 10.7 cm 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.

A resource for Solar-Terrestrial Conditions