ZCZC AP04
QST de W1AW
Propagation Forecast Bulletin 4 ARLP004
From Tad Cook, K7VVV
Seattle, WA January 22, 1999
To all radio amateurs
SB PROP ARL ARLP004
ARLP004 Propagation de K7VVV
Solar activity was up over the past week, with an astonishing jump in solar flux on Wednesday to 238.8. Since this noon reading and the afternoon reading of 210.7 were both solar flare enhanced, we will use the morning measurement of 171.8 for our record book instead.
Looking at the flux values during the nine measurement periods on Tuesday through Thursday, they were 178.4 at 1800z, 175.9 at 2000z, 174.7 at 2200z, then 171.8, 238.8 and 210.7 during the same three periods on Wednesday, and 171.4, 175.3 and 170.5 on Thursday. The reading at noon local time (2000z) in Penticton, BC is the number used for the daily solar flux.
Sunspot numbers for the week averaged nearly 56 points higher than the previous week, and average solar flux was up over 45 points to 159.7. Average solar flux for the same period one year ago was 94.6. Higher activity has meant better conditions on higher frequencies, as increased radiation causes the ionosphere to become more densely charged. When the ionosphere is more dense, then higher frequency signals are reflected and don't pass through into space.
For this weekend expect a rising solar flux, with values of 180, 185 and 180 for Friday through Sunday. Planetary A indices for those days are expected to be around 14, 12 and 10, so some expected unsettled conditions on Friday should quiet down by Sunday. Beyond the weekend, look for solar flux values to drop below 180 after January 25, and below 150 by the end of the month. Flux values are expected to bottom out around 120 from February 3-7, then rise above 150 after February 11, and to 175 by the middle of the month. Unsettled geomagnetic conditions could return around February 9-11.
Last week in VHF news ZL3TIC in Christchurch reported hearing a number of North American stations on 6 meters, as well as low channel commercial television signals. This was on January 14, and the next day WA5IYX in Texas heard a number of 6 meter beacons around North America.
Sunspot Numbers for January 14 through 20 were 86, 106, 106, 131, 169, 182 and 156 with a mean of 133.7. 10.7 cm flux was 136.9, 142.6, 158.5, 161.4, 170.9, 175.9 and 171.8, with a mean of 159.7, and estimated planetary A indices were 26, 17, 7, 5, 5, 5 and 7, with a mean of 10.3