ARRL

ARRL Propagation Bulletin ARLP004 (2002)

SB PROP @ ARL $ARLP004
ARLP004 Propagation de K7VVV

ZCZC AP04
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.
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/EX