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The K7RA Solar Update


On March 6-9, we got a taste of the bad old days from 2008-2009 when there were frequent stretches of 0 sunspots. After March 9, activity picked up and we hope there is no end in sight to the much-welcome sunspots. This week -- March 11-17 -- the average daily sunspot numbers increased from the previous period, from 12.4 to 29.4. Thursday March 18, had a repeat of Wednesday's sunspot number of 28. Sunspot numbers for March 11-17 were 31, 36, 32, 30, 28, 21 and 28, with a mean of 29.4. The 10.7 cm flux was 84.2, 89.6, 91.8, 89.4, 86.4, 85.2 and 86.7, with a mean of 87.6. The estimated planetary A indices were 9, 9, 4, 6, 3, 4 and 7, with a mean of 6. The estimated mid-latitude A indices were 9, 6, 2, 2, 2, 3 and 5, with a mean of 4.1.

We've looked at various moving averages over the past few years to try to smooth out the bumps and spot trends; another way to look at it would be the trailing 50-day average of daily sunspot numbers, which on March 18 was 27.34. The 50 day period is purely arbitrary. For the 18th of each month, going back to April 18, 2009, the trailing 50 day average was 0.48, 2.44, 5.42, 7.4, 3.14, 0.48, 4.42, 7.42, 8.98, 17.44, 26.12 and 27.34. We can see a positive trend there.

On March 11, new sunspot group 1055 emerged, following the arrival of group 1054 the day prior. Group 1055 lasted a very brief period, and group 1056 appeared March 17. Today, group 1054 is fading over the western limb, and it is hard to tell from the STEREO mission if some of the active magnetic areas just over the horizon are new or returning sunspots -- or not even fully formed sunspots at all. One uncertain area looks to be a day or less away, and beyond that, the only thing visible is on the other side of the narrowing unseen area on our Sun's far side. At 1045 Friday morning, that blind spot covers less than 11.7 percent of the Sun's total area.

So far in March, the average daily sunspot number is 24.2. For all of every month of March since the end of the last century, the average (1999-2009) was 100.5, 203.6, 166.7, 154.3, 119.7, 81, 41, 21.3, 9.8, 15.9, and 0.77. Sobering, isn't it?

The vernal equinox, marking the beginning of spring in the northern hemisphere and fall south of the equator occurs tomorrow, March 20 at 1732, 10:32 AM West Coast Pacific Daylight Time, or 1:32 PM EDT. The weeks prior to and following both the vernal and autumnal equinox are favorable to HF propagation.

The latest forecast from Thursday's reading by NOAA and the US Air Force show solar flux remaining in the mid-80s for the next week, and planetary A index staying around 5, until a brief increase to 6 on March 28-29. Geophysical Institute Prague sees quiet conditions for all of March 19-25.

A few comments this week from readers:

"I am fortunate to have #1 DXCC but in recent years have concentrated on 6 meters and the low bands, with lots needed on 17 meters and above. The last month has shown a great improvement in my new ones, with one on 17, 3 on 15, 13 on 12 and two new ones on 10 meters (5N and IS0). Lots more to go for this OT," wrote Pat Rose, W5OZI, of Junction, Texas,

"0300 UTC on March 15 -- 2 hours after local sunset -- I worked ZK3YA and FO8RZ on 12 meters. Makes me wonder if the activity is as much a function of the perception of conditions (that makes amateurs go on the higher bands) as opposed to the conditions themselves. It's not that far into the cycle yet, but everyone is itching to get on 15, 12 and 10 meters," wrote Mark Lunday, WD4ELG, of Greensboro, North Carolina.

"Tuning around on 160 meters on the evening of March 14 showed exceptionally strong SSB signals into Ohio from Virginia and the Carolinas, with very low band noise. I didn't think much of it until the next morning at 1045 when I again heard booming SSB signals from the early morning 160 meter crowd. So I tuned down to CW, and low and behold heard KL7RA (Kenai, Alaska) calling CQ, and then a sked in 9 land, for more than half an hour, working assorted East Coast stations along the way. His signals were a solid 569. Not many takers but he was there to be had," wrote Robert Elek, W3HKK, of Johnstown, Ohio.

A note before closing: In case anyone is confused, when we say 1030 UTC, that is the same as 1030 Greenwich Mean Time. It is also the same as 3:30 AM Pacific Daylight Time or 6:30 AM Eastern Daylight Time.

All times listed are UTC.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.



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