QST de W1AW
Propagation Forecast Bulletin 2 ARLP002
From Tad Cook, K7VVV
Seattle, WA January 11, 2002
To all radio amateurs
SB PROP ARL ARLP002
ARLP002 Propagation de K7VVV
Solar activity has been lower over the past week. Average daily sunspot numbers during the week of January 3-9 were nearly 52 points less than the previous week, and average daily solar flux dropped by 42 points. Along with less sunspots there was very little geomagnetic activity, which is great for HF propagation because of lower absorption. Many periods over the past week had planetary and mid-latitude K indices of 0 or 1.
Solar flux probably reached a short term minimum when it was 188.6 on Monday. Predicted solar flux for Friday through Monday is 230, 235, 240 and 245. Solar flux should peak near 260 around next Thursday or Friday, then reach another short term minimum during the first week of February.
Did we say this week was quiet? This won't last. A high speed stream of energy from a coronal hole is due, and the predicted planetary A index indicates a geomagnetic storm. Values for Friday through Sunday should be around 30, 20 and 15. There was also a large solar flare at 1801z on Wednesday. Although it came from a sunspot near the center of the visible solar disk, the blast of energy from this flare should not bother earth.
AD4JE wrote to suggest a good introduction to HF propagation at http://www.ips.gov.au/papers/richard/prop_intro.html. He also asked about web sites for solar flux, A and K indices, and I referred him to http://www.drao.nrc.ca/icarus/www/current.txt, gopher://sec.noaa.gov/00/indices/DSD and gopher://solar.sec.noaa.gov/00/latest/DGD.
KC7GOL also wrote to suggest NASA's Space Weather site at http://spaceweather.com/.
Several readers wrote to ask about a problem last week using the WA4TTK graphing software with last week's bulletin. This software can grab the data from the bulletin automatically, but last week the use of a phrase in the text of the bulletin which was similar to one at the end in the data area caused a parsing error. WA4TTK has an explanation for these problems and their solutions at http://www.craigcentral.com/solerr.htm. You can download his software at http://www.craigcentral.com/sol.htm. With recent versions of the solar plotting software, you can use the ftp function and grab data from the ARRL to update the data file, instead of entering it by hand or having the software grab the data from your copy of the bulletin.
Sunspot numbers for January 3 through 9 were 229, 248, 201, 143, 158, 143 and 159 with a mean of 183. 10.7 cm flux was 220.3, 218.2, 212.2, 196.6, 188.6, 199.2 and 228.5, with a mean of 209.1, and estimated planetary A indices were 3, 3, 3, 4, 7, 7 and 3 with a mean of 4.3.