[IRCA] Fw: ARLP005 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, February 02, 2007 8:47 AM
Subject: ARLP005 Propagation de K7RA


> SB PROP @ ARL $ARLP005
> ARLP005 Propagation de K7RA
> 
> ZCZC AP05
> QST de W1AW  
> Propagation Forecast Bulletin 5  ARLP005
>>From Tad Cook, K7RA
> Seattle, WA  February 2, 2007
> To all radio amateurs 
> 
> SB PROP ARL ARLP005
> ARLP005 Propagation de K7RA
> 
> Might we see a high-bottom minimum at the end of this solar cycle?
> January had a higher monthly average sunspot number than nine of the
> previous twelve months. Looking at predicted smoothed sunspot
> numbers for 2007, they don't really go any lower this year than what
> is predicted for this month and the next.
> 
> The monthly averages of daily sunspot numbers for all of 2006 and
> January 2007 were 26.7, 5.3, 21.3, 55.2, 39.6, 24.4, 22.6, 22.8,
> 25.2, 14.7, 31.5, 22.2 and 28.2. Average daily solar flux numbers
> over the same months were 83.4, 76.5, 75.5, 88.9, 80.9, 76.5, 75.8,
> 79, 77.8, 74.3, 86.3, 84.4 and 83.5.
> 
> As you can see in the data above, there is a great deal of variation
> from month-to-month. A year ago, in February 2006, the average daily
> sunspot number for the month was only 5.3. That was the lowest value
> for the past year. The month just ended had an average daily value
> over five times the number for last February. In fact, January's
> average at 28.2 would be very close to the value for last February
> squared. But the solar minimum is expected this year, not last
> February.
> 
> A table of predicted smoothed solar values from August 2006 through
> December 2007 can be seen on the web at,
> http://sec.noaa.gov/ftpdir/weekly/Predict.txt. These are Zurich
> sunspot numbers, which tend to be lower than the values we record at
> the end of these bulletins.
> 
> Why is August of last year's number predicted, instead of a known
> value? Because it is a 13 month smoothed number. So it is based on
> the actual sunspot numbers from February 2006 through January 2007,
> and the predicted values for February 2007. Likewise, the smoothed
> number for November 2006 is based on the actual sunspot numbers from
> May 2006 through January 2007, averaged with the predicted numbers
> for February through May 2007. The predicted smoothed sunspot number
> for December 2007, the last value shown on that table, would be
> based on the predicted monthly values for June 2007 through June
> 2008, all averaged together.
> 
> The predicted smoothed numbers from that table, for August 2006
> through December 2007 are 15.4, 15.2, 14.0, 12.4, 11.5, 11.2, 11.0,
> 10.9, 11.0, 11.1, 11.3, 12.0, 11.2, 13.3, 15.6, 18.3, and 21.3. As
> you can see, the lowest value is March 2007, at 10.9, and notice
> that it rises rapidly at the end of this year.
> 
> What difference does higher sunspot activity make for HF
> propagation? As an example, for the middle of February, if the
> average sunspot number was 11, which is about the minimum value if
> there are any sunspots at all, we can compare that with a weekly
> average shown in February 2003 in this Propagation Forecast
> Bulletin: http://www.arrl.org/w1aw/prop/2003-arlp007.html.
> 
> If we pick a couple of locations, for example, Ohio and Spain, we
> can run some projections using a propagation prediction program to
> make some comparisons. The sunspot number in that 2003 bulletin is
> over 150.
> 
> With the minimum sunspot number of 11, a program such as W6ELprop
> (see http://www.qsl.net/w6elprop/) shows a 20-meter path opening
> around 1430z, the signal strength jumping higher around 2000z, and
> the band probably dying out in another hour or so. But with the
> higher numbers, 20-meters is open almost around the clock, with the
> least likely period for propagation around 0430-1130z. On higher
> frequencies, the differences are more dramatic. 15-meters with low
> sunspot activity shows very little chance of opening, with a slight
> possibility in the morning on the Ohio end of the path. But with the
> higher solar activity, strong signals are predicted for 1230-2200z
> on the 15-meter band. Wait a few more years, and we might be there
> again.
> 
> Recently a strong solar wind caused geomagnetic numbers to jump high
> on Monday, January 29 with the planetary A index rising to 36. A
> good place to look for short-term predictions is at,
> http://sec.noaa.gov/ftpmenu/forecasts/45DF.html. For the February 1
> report, we see quiet geomagnetic indices for the next week, with
> higher activity centered on February 13 and again on February 25-26.
> This is based on activity during the current and previous solar
> rotation.
> 
> 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 January 25 through 31 were 11, 11, 11, 13, 27,
> 33 and 32 with a mean of 19.7. 10.7 cm flux was 79.9, 79.7, 80.5,
> 81.7, 86.7, 87.5, and 89.2, with a mean of 83.6. Estimated planetary
> A indices were 1, 2, 3, 5, 36, 21 and 16 with a mean of 12.
> Estimated mid-latitude A indices were 1, 3, 3, 2, 19, 17 and 13,
> with a mean of 8.3.
> NNNN
> /EX
> 
> 
>

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