QST de W1AW
Propagation Forecast Bulletin 5 ARLP005
From Tad Cook, K7RA
Seattle, WA January 30, 2004
To all radio amateurs
SB PROP ARL ARLP005
ARLP005 Propagation de K7RA
There are no sunspots. The visible solar disk is blank. This prompts email inquiring if it's normal to see a spotless sun at this point in the solar cycle. Yes, it is normal, because there are big variations from day to day.
In order to generalize and see the larger trends, we need to calculate a very smooth running average, where readings from many days or months are averaged together. An example of a smooth chart using running or moving averages of many data points can be seen on the web at http://www.ngdc.noaa.gov/stp/SOLAR/SSN/annual.gif or http://www.dxlc.com/solar/cyclcomp.html.
There is an explanation of how a smoothed sunspot number is calculated based on 12 months of averaged data at, http://www.ngdc.noaa.gov/stp/IONO/sunspot.html. There is also a very interesting graphic representation of the difference between a running average based on 12 months and the averages for each individual month over the same period at, http://www.meadows3.demon.co.uk/html/trends.html.
For the 12 months of data there is still a point on the graph for each day, but that point represents all the data from 6 months before and 6 months after, averaged together. The point for the next day is the same, but drops one day off at the back end and averages in another day's data from 6 months in the future. This is why reports showing the current smoothed sunspot number always must be at least 6 months in the past.
In that chart at the previous web link, those tiny colored diamonds each represent a month of averaged data, just like those averages presented frequently in this bulletin. An example of those monthly averages is in 2003's Propagation Forecast Bulletin 49, at http://www.arrl.org/w1aw/prop/2003-arlp049.html.
Jeffrey Philpott, N6QYS wrote to ask if the solar cycle is near bottom, and how long until conditions improve? If we look at the end of a recent (January 6) issue of the NOAA Preliminary Report and Forecast of Solar Geophysical Data at http://www.sec.noaa.gov/weekly/pdf/prf1479.pdf, it shows a projection of future sunspot and solar flux values for nearly the next four years, until December 2007.
This is a rough guess based on previous solar cycles. We can see from both spreadsheets that the predicted bottom of the cycle is expected to occur some time around the end of 2006, although given what we covered above concerning long moving averages, we won't know when the bottom occurs until some time after we've passed it.
We could assume that as we examine projections for rising values during the next cycle, an estimate could be made for when conditions should improve past the current level by looking for a value that matches current conditions. Unfortunately, the data doesn't go that far into the future. The best we can say is that a year from now conditions should be worse, and that the projected number for January 2005 doesn't rise back to that same level until December 2007.
Because January 2005 is a year from now, could we assume that current conditions will worsen and not be at this level again until December 2008? We can't really do that, because solar cycles tend to rise faster than they decline, but a wild guess could be that some time in 2008 conditions will be back up to where they are now. We can all make notes in our PDA to check back to this bulletin in 2008 and see if we were far off base. I've done this, and four years from now I should be quite surprised to see this note from the past.
Conditions will likely improve somewhat over the next week. The weekly average of daily sunspots for this week was half what it was the week before. Average daily solar flux declined over 21 points. Projected solar flux for Friday through Monday, January 30 through February 2 is 90, 90, 100 and 100. Solar flux is expected to peak for the short term around February 8.
Geomagnetic conditions may be rough over the next week, unsettled to active. The predicted Planetary A index for January 30 through February 5 is 15, 20, 20, 25, 25, 15 and 10.
Yesterday's ARRL DX Bulletin reported that this weekend is the UBA DX SSB Contest. The CW section will be in February, but the target in this competition is to work as many European stations on the five non-WARC HF bands, and especially Belgian stations. Working Belgium is worth 3 times the points counted for contacts with other European countries. We won't hazard to guess when 80 and 40 meters should be good for working Belgium or the rest of Europe, but here are some projections for bands higher than 40 meters.
For more information concerning propagation and an explanation of the numbers used in this bulletin see the Propagation page on the ARRL Web site at http://www.arrl.org/tis/info/propagation.html.
Sunspot numbers for January 22 through 28 were 76, 62, 47, 48, 38, 0 and 0 with a mean of 38.7. 10.7 cm flux was 121.8, 115.2, 107.5, 102.3, 98, 93.7 and 88.5, with a mean of 103.9. Estimated planetary A indices were 62, 38, 15, 33, 17, 16 and 19, with a mean of 28.6.