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The K7RA Solar Update


Seven different sunspot groups were visible over the past week. The high sunspot number in the past seven days was 71 on Tuesday, and the average daily sunspot number more than doubled, rising more than 24 points to 44.3. The average daily solar flux was up nearly three points to 83.5. 71 is the highest sunspot number since May 5, 2010 when it was 77. Coincidentally, both February 8, 2010 and February 8, 2011 had a sunspot number of 71, and between those dates, it was never higher except for 77 on May 5.

Sunspot numbers for February 3-9 were 32, 45, 26, 41, 28, 71 and 67, with a mean of 44.3. The 10.7 cm flux was 80.4, 82.1, 81, 80.2, 82.3, 89.7 and 88.7, with a mean of 83.5. The estimated planetary A indices were 1, 21, 13, 11, 3, 4 and 2, with a mean of 7.9. The estimated mid-latitude A indices were 0, 12, 11, 8, 2, 3 and 1, with a mean of 5.3.

The NOAA/USAF prediction for solar flux for the near term improved considerably from what was reported in yesterday’s ARRL Letter. Solar flux is predicted at 90 on February 11-18, then for February 19-25, 88, 88, 86, 84, 84, 80 and 80. They predict a constant planetary A index of 5 through the end of the month, then 7, 10, 10 and 7 on March 1-4. Even though NOAA sees a constant and quiet geomagnetic environment through the end of the month, Geophysical Institute Prague sees it a little differently for February 11-17. They predict quiet on February 11-12, quiet to unsettled February 13, unsettled February 14-16 and quiet to unsettled February 17.

There are a couple of sobering items concerning progress of Solar Cycle 24 and predictions for the peak, now centered around February through July, 2013. Find the latest predicted smoothed sunspot numbers in this week’s Preliminary Report and Forecast #1849.

Dick Wiltgen, K8RBW, of Chicago sent an article from NASA on the latest solar cycle prediction. Note they are using International Sunspot Numbers, which are lower than the Boulder numbers we use in this bulletin and reported in the Preliminary Report and Forecast. Also, at this stage in Solar Cycle 24, predictions are more reliable. Among others, the article cites recent work by Joan Feynman, daughter of the remarkable Nobel Prize winning physicist Richard Feynman.

Ray Perrin, VE3FN, of Ottawa, Ontario sent in a very interesting report of propagation at the start of high geomagnetic activity on February 4: “Just before 2000 on February 4, I was tuning across 15 meters and was surprised to hear a strong signal from a Finnish station on CW. I tuned up the band a bit and heard another Finnish station -- Marko, OH3XR -- working a station in Ohio. I was surprised that I was able to hear the Ohio station as it is very short skip from my location (Ottawa) in Eastern Ontario (grid FN25). But I noticed the signal from the Ohio station was not pure T9.  It also had some slight hiss, which I normally associate with auroral propagation.

“I then worked Mako and he reported that there was a large aurora in progress. This seemed to confirm that I had indeed heard the Ohio station via aurora -- besides, I believe the path was much too short to have been F layer. Marko’s signal was pure T9 and I am unsure as to the mechanism that propagated our signals. My first assumption was that it was auroral E; however, I believe that F-layer propagation can be enhanced after an aurora -- primarily on north-south paths. But my guess is that it was auroral E. After our QSO, I checked the NOAA Space Weather Now site. It was still showing that the auroral zone was fairly quiet and the K index was low. But a little later, it showed an active auroral zone, a K index of 6 and that there was a G1 storm in progress.”.

It is interesting to look at geomagnetic indices on that date, particularly planetary A and K index.

In last week’s bulletin, there was a report from Tamas, HA5PT. He sent along this link and a sound file, to augment his report

All times listed are UTC, unless otherwise noted.

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. You can find a guide to articles and programs concerning propagation here. 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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