Propagation de K7RA

Average daily sunspot numbers and solar flux were up this week, while average daily geomagnetic indices were down, which is a nice combination.

Our reporting week hasn't had better geomagnetic stability (lower average A index) since November 16-22, 2006,
reported in last year's Propagation Forecast Bulletin ARLP049

That week the planetary and mid-latitude A indices were 3.6 and 2.1, while this week's numbers are 5.6 and 4.3.

Conditions won't remain quiet, and geomagnetic activity should increase until next Tuesday, February 13. Geophysical Institute Prague predicts quiet to unsettled conditions for today, February 9, quiet conditions on February 10, unsettled to active February 11, unsettled February 12, active geomagnetic conditions on February 13, unsettled to active on February 14, and February 15 unsettled.

The US Air Force predicts a planetary A index for February 9-15 at 5, 5, 20, 20, 20, 15 and 5. For those same days they predict solar flux values of 80, 83, 83, 81, 80 and 80.

We keep mentioning the bottom of the sunspot cycle, and by some accounts, we are probably there, or very close. NOAA Space Environment Center has a new prediction in this week's Preliminary Report and Forecast of Solar Geophysical Data at, http://www.sec.noaa.gov/weekly/pdf/prf1640.pdf. Look at the table on page 10, and compare it with the table on page 9 in the report from five weeks earlier, http://www.sec.noaa.gov/weekly/pdf/prf1635.pdf.
These are predicted smoothed sunspot numbers, averaged over a year, going six months prior and six months into the future for each month.

Notice in the most recent report that the latest smoothed sunspot number not in bold lettering is July 2006. That is because the real sunspot data actually exists for six months after that month, and this is the actual smoothed sunspot number, an average of averages, made up from the monthly averages for January 2006 through January 2007. If you check the report from five weeks ago, July 2006 is bold, because there was one month for which actual sunspot numbers weren't actually yet known, January 2007. So in the latest report, the number for October 2006 factors in three predicted but as yet unconfirmed monthly averages, February through April 2007, and December includes predicted numbers for five months, February through June 2007.

So in the early January report, you can see that the numbers for October 2006 through August 2007 were 13, 11, 10, 10, 10, 10, 10, 10, 10, 10 and 11. The most recent prediction for those same months was 14, 12, 12, 11, 11, 11, 11, 11, 11, 12 and 11. Both reports seem to place us at the bottom. The other clue is at, http://sec.noaa.gov/ftpdir/weekly/Predict.txt where the predicted smoothed sunspot number is 10.9 for March 2007, with 11 for both this month and April. March 2007 would be the lowest predicted smoothed sunspot number shown in this table.

Randy Crews, W7TJ of Spokane, Washington wrote to comment after last week's summary of monthly sunspot averages in Propagation Forecast Bulletin ARLP006 (see
http://www.arrl.org/w1aw/prop/2007-arlp005.html).
Randy thinks that the actual low for cycle 23 was last year, in February 2006, when the average sunspot number for the month was only 5.3. Another way to look at this is with a 3-month moving average based on an average of the daily sunspot numbers, instead of an average of averages, as the 13 month smoothed number is. So for December 2006 we would get an average of 27.2 by summing all of the sunspot numbers from November 1 through January 31, which yields 2507, and dividing by the number of days, which is 92.

Here is a table of the 3-month average of daily sunspot numbers for a 13-month period:

Dec 05 40.6
Jan 06 32.4
Feb 06 18.1
Mar 06 27.7
Apr 06 38.5
May 06 39.7
Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3

The number shown for each month is the average for the daily numbers for that month combined with the month preceding and the following month. This still shows a low minimum centered on February 2006.

W7TJ says he likes the sunspot minimum because there are very few days with disturbed conditions. He says, "What I am looking forward to is a quiet Sun, absent of CMEs, coronal holes, X-Ray radiation etc, that ruin propagation." And of course, since the MUF is lower because of the lower solar activity, this really is the best time for 80 and 160-meter propagation.

Now as we move toward mid-February, we are further from the darkest day of the year, and half way toward the Spring equinox, which is a good time for HF propagation. What will HF propagation be like from your location today? This will vary according to which amateur band you use and what part of the world you are targeting.

This bulletin has mentioned W6ELprop in the past, and you can use this software to come up with unique propagation projections from your location, much better than we could do in this bulletin by generalizing for a region. You can get the software from, http://www.qsl.net/w6elprop/. A good method is to take an average of the three most recent sunspot numbers, and use that figure with W6ELprop.
You can get those numbers from, http://www.sec.noaa.gov/ftpdir/indices/DSD.txt.

So if it is Friday morning, February 9, the average would be based on the sunspot numbers from February 6-8, which were 23, 23 and 22. That averages to about 22.7. When you enter that number into W6ELprop, whether you have it set to take sunspot number or solar flux, you can always get the right choice by preceding the sunspot number with the letter S. So that would be S22.7 for today.

W6ELprop will also work with the K index, and you can get the current mid-latitude K index from WWV. The current WWV numbers are always available at, http://sec.noaa.gov/ftpdir/latest/wwv.txt.

Of course, you will want to customize the program for your own location, based upon latitude and longitude. There are a variety of ways to find these coordinates, but one easy method that gets you close enough is to do a ZIP Code search at, http://www.gpsvisualizer.com/convert?
form=address.

Be careful when you enter the numbers, because W6ELprop expects west longitude as a positive number, and on this web site they use the common standard in which east longitude is positive. So for those of us west of Greenwich, England, the prime meridian, we would turn that negative
longitude into positive for the W6ELprop software.

Given the average sunspot number for the previous few days, suppose we are in Atlanta, Georgia, and want to know what the bands will be like toward Brazil. If this is the first time using the program, we can set up our location by clicking on Options at the top.

To make a projection, bring up the program, click on Predictions at the top, then select On-Screen from the drop-down menu, and then use the tab key to navigate through the various fields, entering PY for Brazil in the Prefix or Locator field. When the calculation is made, we can see that as the MUF rises above 22 MHz, 15 meters would likely open around 1330z. Signals should stay strong during the day,
and get stronger before dropping out around 2300z when the MUF drops below the 15-meter band.

A great propagation program is ACE HF Pro, which gives some very fine graphic visualizations of propagation. You can learn about it from, http://www.hfradio.org/ace-hf/ or from,
http://home.att.net/~acehf/. That first link was from Tomas Hood, NW7US, who in addition to editing the monthly propagation column for CQ Magazine, has a fine web site devoted to radio propagation. It has been offline for several months, but is back on at, http://hfradio.org/backon.html.

If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net.

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 February 1 through 7 were 31, 36, 35, 28, 25, 23 and 23 with a mean of 28.7. 10.7 cm flux was 89.9, 90.3, 87.3, 83.7, 83, 81.9, and 82, with a mean of 85.4. Estimated planetary A indices were 8, 2, 3, 2, 6, 8 and 10 with a mean of 5.6. Estimated mid-latitude A indices were 7, 2, 1, 2, 4, 6 and 8, with a mean of 4.3.

Source: The American Radio Relay League

• All propagation reports can be found at:
http://www.southgatearc.org/propagation