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The K7RA Solar Update

03/12/2021

Tad Cook, K7RA, Seattle, reports: Although solar activity remains low, in recent days, as a sunspot rotates to the west off the visible solar disc a new one emerges in the east. Sunspot group 2807 recently moved over the sun’s western horizon, but on March 9 new sunspot group 2808 moved across the eastern horizon, and a newer group (2809) has now emerged just south of the center of the solar disc. This brought the daily sunspot number higher from 11 on Wednesday to 23 on Thursday, March 11.

Recent sunspot activity and solar flux still seem soft when compared to activity toward the end of 2020, however.

In Bulletins ARLP048, 49, and 50 in 2020 — covering November 19 – December 9 — average sunspot numbers were 27.9, 57.6, and 28.9, while average daily solar flux was 90.1, 108.1, and 91.9. For the past 3 weeks, the overall average daily sunspot numbers was 19 (2 weeks prior had no sunspots), and average daily solar flux was 77.1.

We can’t do anything but wait and watch, although we can look forward to the vernal equinox on Saturday, March 20. Like the autumnal equinox, this is always a positive influence on HF propagation, when the northern and southern hemispheres are bathed in approximately equal amounts of solar radiation. You can count on it.

The average daily sunspot number this week hardly changed, from 18.9 last week to 18.4. Average daily solar flux shifted marginally higher from 76.7 to 78.9.

Solar wind has slackened, so average daily planetary A index went from 14.7 to 7.6, and the middle latitude numbers changed from 10.4 to 6.1.

Predicted solar flux for the next 30 days is 78 on March 12 – 19; 75, 76, 78, and 81 on March 20 – 23; 80 on March 24 – 25; 78 and 76 on March 26 – 27; 75 on March 28 – April 1; 78 on April 2 – 3, and 70, 74, 76, 72, 71, 72 and 70 on April 4 – 10. After April 18, solar flux may rise again above 80, then back to 75 by April 24.

Predicted planetary A index is 12, 20, and 10 on March 12 – 14; 5 on March 15 – 17; 12 on March 18 – 19; 20, 18, 12, and 8 on March 20 – 23; 5 on March 24 – 27; 25, 20, 20, and 10 on March 28 – 31; 5, 15, and 8 on April 1 – 3; 5 on April 4 – 7, and 18, 12, 5, and 15 on April 8 – 11. A recurring coronal hole may rotate into a geo – effective position on April 15 – 16 and another around April 24 – 25, raising the planetary A index again to around 20 – 25.

Here’s the geomagnetic activity forecast for March 12 – April 6 from F.K Janda, OK1HH.

The geomagnetic field will be:

  • quiet on March 17, (26 – 27,) April 1, 6
  • quiet to unsettled on March 12 – 13, 16, 25, April 3 – 5
  • quiet to active on March 21 – 24, 31
  • unsettled to active March 14 – 15, 18, 29 April 2
  • active to disturbed March 19 – 20, 28, 30
  • Solar wind will intensify on March (12 – 14, 18 – 19,) 20 – 23, (27,) 28 – 31, April (1 – 2)

Parenthesis means lower probability of activity enhancement. Predictability of changes remains very low, as there are ambiguous indications.

Dennis, K7BV, reported: “March 7, while checking the bands for DX, I went to 15 meters on FT8 about 1650. The strongest signal by a huge margin was S79KW (LI75rj Seychelles) at +27 dB! After a quick contact, I moved to a clear frequency to call CQ.  Almost immediately 4S6RSP, –8 dB strong. called. A few minutes later VU2AMW at –1 dB called. I also noticed YC5YZ calling CQ. Nothing else heard from the region, but S79KW remained strong well after this brief 15-meter opening to Southern and Southeast Asia.” 

Unfortunately the averages at the end of this bulletin sometimes change from the preview that appears in Thursday’s edition of The ARRL Letter. This is my fault and happens from time to time. Thanks so much to Don Wright, AA2F, who catches these every time, and makes sure the correct averages appear in Friday’s bulletin.

Aurora season has returned in Colorado.

David Moore sent this from Science News: “The aurora’s very high altitude booster.”

Sunspot numbers for March 4 – 10 were 32, 14, 23, 14, 12, 23, and 11, with a mean of 18.4. The 10.7-centimeter flux was 81.4, 73.2, 77, 77.5, 79.9, 83.7, and 79.4, with a mean of 78.9. Estimated planetary A indices were 11, 5, 16, 10, 6, 3, and 2, with a mean of 7.6. Middle latitude A index was 11, 5, 11, 7, 5, 2, and 2, with a mean of 6.1.

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.

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