QST de W1AW
Propagation Forecast Bulletin 4 ARLP004
From Tad Cook, K7VVV
Seattle, WA January 25, 2002
To all radio amateurs
SB PROP ARL ARLP004
ARLP004 Propagation de K7VVV
Average sunspot numbers rose over 9 points this week, and average solar flux dropped nearly 8 points, so solar activity was about the same as last week. There weren't any days with big geomagnetic upsets. Saturday was slightly unsettled, with the planetary K index at 4 over two of the 3-hour reporting periods. Because of lower indices earlier, the planetary A index for the day was only 11. As mentioned last week, for information on the relationship between the daily A index and the eight-times daily K index, check http://www.ngdc.noaa.gov/stp/GEOMAG/kp_ap.html .
Latest projections show stable geomagnetic conditions well into next month, with planetary A indices in the low and mid single digits. This is generally good for HF operators because of lower absorption. Predicted solar flux for Friday through Sunday is 225.
NASA reported this week that the previous two solar cycles were double-peaked, and the current one is also. At one time we believed that Cycle 23 peaked in mid-2000, but then a larger peak emerged in late 2001. No doubt this explains all that fabulous F2 layer propagation on 6 meters last fall. You can read NASA's story on the web at http://science.nasa.gov/headlines/y2002/18jan_solarback.htm .
Here are some general observations about HF conditions from the continental U.S. over the next few weeks.
Toward Europe, 80 and 40 meters open right after local sunset and stay good until the wee hours after midnight. 30 meters works all day and night, but is weakest during local mid-morning in the east and Midwest, and before sunrise on much of the west coast. 20 meters opens around sunrise. In the Midwest and east, conditions are best an hour or two before local sunset. This decreases as you move west, where 20 meters closes down before local sunset. 17 and 15 meters open around sunrise, and close earlier than 20 meters. 12 and 10 meters open for most of the U.S. about two hours after sunrise and close a few hours before sunset, but this shortens considerably as you move west.
Toward South America, 80 meters is best three hours after sunset until after midnight, and 40 meters one hour after sunset and closing an hour after 80 meters. 30 meters should be open from sunset until a few hours before sunrise, and 20 meters from before sunset until about four hours before sunrise. 17 and 15 meters should open around sunrise until two hours after sunset, and 12 and 10 meters from after sunrise until sunset.
Toward East Asia (Japan) 80 and 40 meters are best after midnight until an hour before sunrise. But on the West Coast, both bands should stay open until about an hour after sunrise. 30 meters is good from early evening until sunrise in the central states, but should be dead from the east coast during the early evening. On the West Coast 30 meters should be good from the late evening until an hour after sunrise. 20 meters should be best around sunset until the mid to late evening, but on the West Coast 20 meters is best from the mid until late evening, then again from local sunrise until about two hours later. 17 and 15 meters should be best for about four hours centered around local sunset, except on the West Coast where it lasts around six hours. 10 and 12 meters should be open for 1-2 hours around sunset, except on the West Coast where it should last around four hours.
Remember that the sunrise, sunset and times of day are for your location. As an example, local sunset in New York City is around 2200z, and in Central California it is after 0100z.
The above predictions are very general. To get a more accurate reading specific to your location, use W6ELprop to predict paths using the average solar flux for the previous few days. As mentioned in previous bulletins, you can download this free propagation predicting program at http://www.qsl.net/w6elprop/ . If you want to check some of the material presented in past bulletins, go to http://www.arrl.org/w1aw/prop/ .
Sunspot numbers for January 17 through 23 were 122, 156, 153, 212, 187, 178 and 272 with a mean of 182.9. 10.7 cm flux was 211.8, 210.5, 213.7, 222.2, 224.5, 228.7 and 226.5, with a mean of 219.7, and estimated planetary A indices were 6, 5, 11, 7, 9, 6 and 6 with a mean of 7.1.