QST de W1AW
Propagation Forecast Bulletin 2 ARLP002
From Tad Cook, K7VVV
Seattle, WA January 14, 2000
To all radio amateurs
SB PROP ARL ARLP002
ARLP002 Propagation de K7VVV
Sunspot activity and solar flux were up over the past week. Average solar flux rose over 30 points to 163.8 and average daily sunspot number was up over 50 points to 136.6 compared to the previous week.
Geomagnetic conditions were quieter over the past week. This is important for good HF propagation, because higher geomagnetic activity (reflected in the daily A index and the K index measured every three hours) results in higher absorption of HF radio waves.
The most recent active period was from December 31 to January 6, when the planetary A index was as high as 27 on New Year's Eve day and on New Year's Day. When solar activity such as flares or coronal holes bombard the earth with protons, polar regions experience the greatest effect. As a result, daily A indices taken in Alaska on December 31 and January 1 were 40 and 44, with K indices as high as six.
When the solar surface relative to earth rotates this same active region toward us about 27.5 days after the recent activity, we could see similar effects around January 26 until February 3. A recent forecast shows the planetary A index rising to 25 on January 27 and 28, then drifting down gradually to unsettled conditions with an A index of 10 on January 31. The next few days may see a rise in activity, with the A index peaking again near 20 around February 2.
Solar flux has been rising this week, with a greater than 14 point rise from Monday to Tuesday and a greater than 18 point rise on Wednesday. The forecast for this weekend, Friday through Sunday, is for solar flux to rise from 205 on Friday to 210, and then 215 on Sunday, with a wonderfully low planetary A index of 5 for all weekend.
HF operators should be very happy with a rising solar flux combined with low geomagnetic activity. Beyond the weekend expect the solar flux to remain high until around January 20, finally drifting down to around 135 for the period from January 26 to February 1.
A group of seventh graders at Ritchie County Middle/High School in Ellenboro, West Virginia sent an interesting note and graph. They kept track of the weekly average of sunspot numbers through November and December, and at night logged AM radio stations. Their graph correlates the maximum skip distance with the rise and fall of sunspot numbers.
Also arriving in this week's postal mail were some charts from NOAA Space Environment Center showing the new Space Weather Scales, which are numeric ratings for radio blackouts, solar radiation storms and geomagnetic storms. Each is rated from 1 through 5.
The worst radio blackout is an R5, and the effect is described as ''complete HF radio blackout on the entire sunlit side of the earth lasting for a number of hours. No HF radio contact with mariners or en route aviators.'' It notes that there is less than one R5 event per solar cycle.
For a G5 rated geomagnetic storm, which averages four days per solar cycle, it says that power system grids can collapse and transformers experience damage. Pipeline currents can reach hundreds of amps, HF radio propagation is impossible for one to two days, and the aurora can be seen from the equator. A G5 rating corresponds to a K index rating of 9! K indices of 9 over a 24 hour period would result in an A index of 400, which is not a pleasant thought for HF operators.
You can see descriptions of these Space Weather Scales at http://www.sec.noaa.gov/NOAAscales/index.html.
As a final note, check out the web-based Space Physics Textbook at http://www.oulu.fi/~spaceweb/textbook/Welcome.html.
Sunspot numbers for January 6 through 12 were 145, 146, 106, 119, 88, 148 and 204 with a mean of 136.6. 10.7 cm flux was 144.8, 149.8, 154.7, 160.6, 163.2, 177.6 and 195.7, with a mean of 163.8, and estimated planetary A indices were 17, 8, 6, 3, 6, 16 and 9, with a mean of 9.3.
Our path projection for this week is from Ellenboro, West Virginia, the home of KC8KOH, the Ritchie County Middle/High School Amateur Radio Club.