ARRL

ARRL Propagation Bulletin ARLP030 (2000)

SB PROP @ ARL $ARLP030
ARLP030 Propagation de K7VVV

ZCZC AP30
QST de W1AW  
Propagation Forecast Bulletin 30  ARLP030
From Tad Cook, K7VVV
Seattle, WA  July 28, 2000
To all radio amateurs 

SB PROP ARL ARLP030
ARLP030 Propagation de K7VVV

Solar flux and sunspot numbers were down only slightly this week
from last. Last week's average sunspot numbers were up over 40
points from the previous week, and this week's are down less than 7.
But the big news this week should be the big peak in sunspot numbers
on Thursday, July 20, when it reached 401. This is a rare, high
number in any solar cycle, and the biggest so far in cycle 23.

A cursory examination of the data shows that the sunspot number has
not been this high since August 23, 1991, when it was 478. Sunspot
numbers over 400 suggest that we may be nearing the cycle peak.

The latest projection the author has seen for cycle peak is from the
July 4 Preliminary Report and Forecast of Solar Geophysical Data
from the NOAA Space Environment Center (on the web at
http://www.sec.noaa.gov/weekly/index.html ). It shows smoothed
monthly solar flux peaking in August or September, but smoothed
sunspot numbers peaking around next January or February.

The latest short term projections show some rough weather ahead for
the weekend, with the planetary A index for Friday through Tuesday
at 30, 25, 12, 12 and 10. Projected solar flux for those same five
days is 160, 155, 155, 150 and 145. Solar flux should rise above 200
by August 4, then reach 230 on August 8-14, and peak around 235 on
August 15-16.

WF7M wrote to ask about geomagnetic indices for Alaska. This is
identified as the College index at
gopher://solar.sec.noaa.gov/00/latest/DGD . These values are
generally higher than the mid-latitude or planetary indices.

The author of this bulletin is off on a short vacation via train,
and next week K9LA has graciously agreed to write the bulletin.

Sunspot numbers for July 20 through 26 were 401, 325, 290, 276, 215,
232 and 214 with a mean of 279. 10.7 cm flux was 252.9, 250.9, 251,
217.3, 224.8, 201.8 and 174.6, with a mean of 224.8, and estimated
planetary A indices were 43, 9, 18, 20, 8, 7 and 20, with a mean of
17.9.
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/EX