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The K7RA Solar Update

03/05/2021

Tad Cook, K7RA, Seattle, reports: We saw one day during the February 25 – March 3 reporting week — Monday, March 1 — with no sunspots, so the average daily sunspot number declined slightly from 19.6 to 18.9. Two new sunspot groups (2806 and 2807) appeared on Tuesday, March 2.

Average daily solar flux increased only slightly during the reporting week, from 75.7 to 76.7.

Average daily planetary A index softened slightly from 16 to 14.7, and the middle latitude average went from 12.4 to 10.4. Geomagnetic indicators remained somewhat active due to persistent solar wind. The most active day was Monday, when Alaska’s high-latitude College A index reached 34.

Spaceweather.com reported a G2 class geomagnetic storm on Monday, aided by a significant crack in Earth’s magnetic field. Although activity was otherwise moderate this week, the March 1 event was the largest storm since a G3 event 94 weeks earlier, on May 14, 2019.

Predicted solar flux for the next 30 days is 80 on March 5; 78 on March 6; 78 on March 7 – 9; 72 on March 10 – 11; 71, 72, 70, 71, 72, and 71 on March 12 – 17; 73, 76, 75, 76, 78, and 81 on March 18 – 23; 80 on March 24 – 25; 79, 78, and 73 on March 26 – 28; 74 on March 29 – 30; 73 on March 31 – April 1, and 74 on April 2 – 3.

Predicted planetary A index is 10, 20, and 15 on March 5 – 7; 10 on March 8 – 9; 8, 5, 15, 10, and 5 on March 10 – 14; 15, 8, 5, and 18 on March 15 – 18; 20 on March 19 – 20; 18, 12, and 8 on March 21 – 23; 5 on March 24 – 27; 20, 15, and 10 on March 28 – 30; 5 on March 31 – April 1; 12 on April 2, and 5 on April 3 – 7.

Here’s the geomagnetic forecast for Marcy 5 – 30 from J. K. Janda, OK1HH. The geomagnetic field will be:

  • quiet on March 9 – 10, 14, (26 – 27)
  • quiet to unsettled on March 5, 16 – 17, 25
  • quiet to active on March 7 – 8, 11, 13, 15, 20 – 24
  • unsettled to active March 12, 29
  • active to disturbed March 6, 18 – 19, 28, 30
  • Solar wind will intensify on March (5 – 9, 12 – 14, 16 – 22, 27,) 28 – 29

Parentheses mean lower probability of activity enhancement.

Predictability of changes remains low.

W6MVT reports a surprising 10-meter opening to South America on the same Tuesday when sunspots re-appeared.

“It never hurts to turn on 10 meters or check the spots on DXMaps or your favorite spotter. I saw some action and was pleased I was at the radio. On March 2 around 2130 UTC 10-meter SSB was alive with South American stations and a good path to those of us in Southern California. With 100 W and a rotatable dipole only up 20 feet, I was able to log LU4DJB, PU2LUC, PY2EX, PY5QW, PU2SDX, and PY4NY in rapid succession, all with good reports both ways. Things faded out around 2200 UTC, but I was glad I caught it.”

Larry, K8MU, sent this item concerning a space plasma hurricane. Don’t miss Larry’s page on QRZ.com, showing lines and arrows with humorous text about his modest station, complete with steerable ground plane and incoming QSL receptacle.

This is from an email exchange with Frank Donovan, W3LPL, regarding Total Sunspot Area, which is shown daily along with SFI and SSN (Sunspot Number) in this table. (SFI is 10.7-centimeter solar flux, uHem (micro hemispheres) is solar micro hemispheres, and EUV is extreme ultraviolet radiation.)

“Here are some additional insights regarding total sunspot area. SFI and total sunspot area are well correlated with each other and with EUV flux at the wavelengths that ionize the F2 region. Daily sunspot number is not well correlated, because tiny sunspots greatly affect it but have no effect on HF propagation. I usually ignore daily sunspot numbers unless total uHem exceeds 200.

“Today is a classic case with daily SILSO sunspot number = 30, but total sunspot area is under 100 uHem and SFI is stuck at 75.

“Roughly 100 uHem elevates the SFI into the mid 70s but has only a minor effect on HF propagation.

“200 uHem roughly corresponds to SFI = 80 and usually improves 17 and 15 meter propagation. But, the normal daily variability of F2 MUFs is not well correlated to SFIs of about 80 and often swamps out the expected improvements from SFI = 80.

“HF MUFs increase more consistently when the SFI approaches 90. You may recall active region 12786 area was as high as 1,000 uHem last November, and the SFI was above 100 for 9 days. It greatly improved 15-meter propagation during the CQ World Wide DX CW contest, and there was significant 10-meter DX propagation too. Daily sunspot number varied wildly from 40 to 94 during this period, mostly because there were also three smaller active regions at during the period when 12786 was by far the most significant contributor to SFI greater than 100.

“The rough equivalencies are uHem to SFI:

100 = 75; 200 = 80; 400 = 90; 600 = 100; 800 = 110; 1,000 = 120; 1,200 = 130; 1,400 = 140; 1,500 = 150; 1,600 = 160; 1,800 = 170, and 2,000 = 180.”

This weekend is the ARRL International DX Contest (phone).

Here’s a NASA video of a solar flare from Science Times.

This is a recent video forecast from the Space Weather Woman Tamitha Skov, WX6SWW.

Sunspot numbers for February 25 – March 3 were 31, 16, 14, 13, 0, 28, and 30, with a mean of 18.9. The 10.7-centimeter flux was 80.1, 80.1, 79.2, 77.7, 71, 74.7, and 74.2, with a mean of 76.7. Estimated planetary A indices were 13, 11, 4, 6, 26, 20, and 23, with a mean of 14.7. Middle latitude A index was 13, 8, 3, 4, 16, 14, and 15, with a mean of 10.4.

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.

Share your reports and observations.

 

 



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