[IRCA] Fw: ARLP016 Propagation de K7RA

["Art Blair" <artngwen@xxxxxxxxxx>]

----- Original Message ----- 
From: "W1AW Mailing List" <w1aw-list-request@xxxxxxxxxxxxxxxxx>
To: <artngwen@xxxxxxxxxx>
Cc: <W1AW List:>
Sent: Friday, April 13, 2007 7:05 AM
Subject: ARLP016 Propagation de K7RA


> SB PROP @ ARL $ARLP016
> ARLP016 Propagation de K7RA
> 
> ZCZC AP16
> QST de W1AW  
> Propagation Forecast Bulletin 16  ARLP016
>>From Tad Cook, K7RA
> Seattle, WA  April 13, 2007
> To all radio amateurs 
> 
> SB PROP ARL ARLP016
> ARLP016 Propagation de K7RA
> 
> So far this month we've observed 9 days in a row with 0 sunspots,
> and all of our reporting week for this bulletin (April 5 through 11)
> falls within this string of inactive solar days. As noted in last
> week's bulletin, comparing that week's average sunspot number (12.9)
> to this week's (0) doesn't mean much when activity is so low at the
> bottom of this sunspot cycle. Based on predicted smoothed sunspot
> numbers, if this month and the next are truly the solar minimum, we
> should probably see several weeks in a row with no sunspots.
> 
> Those hoping for more activity and a return to worldwide propagation
> on 10 and 15 meters should be cheered by this, because recent
> observation shows the rise of any solar cycle is faster than its
> decline, and most importantly, the decline of the previous cycle.
> 
> Around the last solar minimum, between Cycles 22 and 23, Sun
> watchers observed several long strings of days showing no sunspots.
> For instance, from February 10 to March 5, 1997, the average sunspot
> number was 2.1, and there were 20 days during that period with no
> sunspots. Prior to that, another long stretch of inactivity occurred
> in the Fall of 1996. The average daily sunspot number was 1.7 from
> September 5 to November 8, when 57 of 65 days the Sun showed no
> spots. The longest continuous stretch with no sunspots at all in
> that period was 38 days, following September 12, when a single
> sunspot was visible and ending October 21, when another sunspot
> appeared. Both those days had an official sunspot number of 11, and
> each time, the single sunspot was only visible for a single day.
> 
> This period was preceded and followed by three days of no sunspots,
> and October 29 through November 8, 1996, also had zero sunspots,
> followed by December 24 through January 3, 1997.
> 
> Remember that an average sunspot number of 1 or 2 doesn't correspond
> to one or two sunspots. Because of the peculiar manner in which
> sunspot numbers are derived, the minimum non-zero sunspot number on
> any day is 11. This is because the number of sunspot groups is
> multiplied by ten, and the resulting number is added to the total
> number of visible spots. So two spots in one group is 12, three
> spots is 13, but three spots in two groups yields a sunspot number
> of 23.
> 
> To observe the rate that the end of Cycle 22 fell toward minimum and
> the beginning of Cycle 23 began, it is useful to average sunspot
> numbers over each quarter. The average sunspot numbers for the years
> 1993 and 1994 were 79 and 48. The averages for the four quarters of
> 1995 were 47.4, 25.3, 21 and 21.3. 1996 had 13.1, 13, 12.4 and 14.2.
> For 1997, the quarterly averages were 11.3, 25.4, 37.2 and 48.2. The
> quarterly averages of sunspot numbers for the next two years, 1998
> and 1999 were 62.9, 80.4 , 111.8, 99.1, 97.2, 147.2, 137.9 and
> 163.1. You can see that the new cycle rose quickly, beginning in the
> second quarter of 1997.
> 
> In practical terms, what is the difference between a couple of weeks
> of zero sunspots, and three months of a sunspot number around 163?
> 
> As an example, every year Saad Mahaini, N5FF of Richardson, Texas
> spends three weeks in Syria. Currently operating YK1BA, he will
> return to Texas on April 28.
> 
> Plugging the numbers into a popular propagation prediction program,
> this weekend when he talks to someone back home in the Dallas area,
> he might find spotty openings on 20 meters around 2100-2230z and
> perhaps 0400z. Less likely, 17 meters might be possible around
> 1700-2000z, and far less likely, 15 meters from 1500-2100z. He could
> also expect strong 40-meter signals from 0000-0400z. These are
> normative expectations. Your mileage may vary. Saad may experience
> fantastic propagation. These are based on probability, and we can
> always be surprised.
> 
> But if the sunspot number leading up to this weekend had been about
> 163, he could expect stronger 40 meter signals over the same period,
> 20 meter propagation from 2100-0700z with really strong signals from
> 0000-0430z, and a good 15 meter opening from 1300-2300z. He might
> even find 10 meters open over a shorter time during the same period.
> Or, the Sun could be covered with spots, and a huge solar flare --
> more likely during periods of higher solar activity -- could wipe
> out propagation in a radio blackout.
> 
> Coming soon, the prediction for the next period of unsettled
> geomagnetic conditions is for around April 20, with an expected
> planetary A index of 20. After that, a planetary A index of 25 is
> predicted for April 28. This same forecast (from the U.S. Air Force,
> via NOAA) shows solar flux of 70 until April 16, when it rises to
> 75. This is a small shift, but may signal the period during which we
> could see another sunspot, April 16-27.
> 
> David Moore tipped us off to an interesting article from the
> European Space Agency about the physics of solar wind and auroras.
> The link for that article is at,
> http://sci.esa.int/jump.cfm?oid=40878 .
> 
> Finally, one more report from the top of Cycle 19. John Hardin, W4NU
> of Atlanta, Georgia was first licensed around the age of 16 as
> KN4JAG in Atlanta in June 1959, and upgraded to General class a
> month later. He writes: "The propagation was awesome. By 1960 I
> upgraded from a Knight Ocean Hopper receiver and Globe Scout 680-A
> with a 40 meter doublet to a Viking Valiant, NC-57B receiver, and a
> 3 el Hornet Tribander on my parents' roof. 10 meters was open after
> midnight, 15 on into the morning and 20 meters all night. I could
> break the DX pileups with ease and ended up with DXCC in the early
> 1960s. I will never forget how crowded the 10 meter phone band was."
> 
> If you would like to make a comment or have a tip for our readers,
> email the author at, k7ra@xxxxxxxxx
> 
> For more information concerning radio propagation, see the ARRL
> Technical Information Service at,
> http://www.arrl.org/tis/info/propagation.html. For a detailed
> explanation of the numbers used in this bulletin see,
> http://www.arrl.org/tis/info/k9la-prop.html. An archive of past
> propagation bulletins is at, http://www.arrl.org/w1aw/prop/ .
> Monthly propagation charts between four USA regions and twelve
> overseas locations are at, http://www.arrl.org/qst/propcharts/.
> 
> Sunspot numbers for April 5 through 11 were 0, 0, 0, 0, 0, 0 and 0
> with a mean of 0. 10.7 cm flux was 70.9, 71, 71.2, 71.1, 69.9, 69.4,
> and 69.1, with a mean of 70.4. Estimated planetary A indices were 4,
> 4, 3, 3, 9, 7 and 4 with a mean of 4.9. Estimated mid-latitude A
> indices were 3, 2, 2, 2, 8, 6 and 3, with a mean of 3.7.
> NNNN
> /EX
> 
>

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