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ARRL Propagation Bulletin ARLP009 (2002)

ARLP009 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 9  ARLP009
From Tad Cook, K7VVV
Seattle, WA  March 1, 2002
To all radio amateurs 

ARLP009 Propagation de K7VVV

This was another quiet week for geomagnetic conditions. The average
planetary A index declined slightly from 6 to 5.4, and all daily
geo-indices were in the single digits. This was great for the CQ
160-meter contest last weekend.

Solar flux and sunspot numbers rose. Combined with low K and A
indices, this indicates good HF radio conditions. Average daily
sunspot numbers rose over 45 points from last week, and average
daily solar flux was up nearly 5 points.

Solar flux has been hanging around 200, and this is expected to
continue. Current projections show flux values right around 200 over
the next several weeks, but of course new solar activity could
emerge to change this.

On Thursday a minor geomagnetic storm began around 1700z. Planetary
A indices reached 17, a level not reached in the quiet conditions of
the past few weeks. Conditions will probably quiet down in time for
the phone weekend of the ARRL International DX Contest, which begins

KC1QF is an astronomer at the Tohono/Steward 12-meter Radio
Observatory at Kitt Peak. You can see a virtual tour of the 12-meter
telescope at . Peter didn't send in that URL, but
he did send a couple of links to interesting web sites that show
live sun images. They are and . The first
image is live 24 hours a day, with the source of the image shifting
as the earth turns.

AE4TM wrote about the double peak of the current solar cycle, and
said that during this second peak we are experiencing more
backscatter propagation. He refers us to his web site at , and writes ''Backscatter
propagation is occurring almost daily with RF distances extending up
to 2700 miles for stations just beyond the line of sight (50-100
miles)! These are due to significantly higher electron densities in
the ionosphere compared to the first peak in the current solar
cycle. These higher electron densities lead to higher frequencies
that can reflect vertically (termed f0F2) and these higher densities
also allow for complex curvatures in the RF paths between two radio
stations increasing the likelihood of rare DX contacts.''

K9LA wrote to say that the monthly median MUF for December 2001 was
about 2 MHz higher than December 2000, according to data from an
ionosonde in Abilene, Texas. He looked at monthly median f0F2 for
the two periods.

Sunspot numbers for February 21 through 27 were 148, 161, 176, 191,
237, 223 and 192 with a mean of 189.7. 10.7 cm flux was 201.1,
191.9, 188.2, 192.8, 210.6, 207.5 and 198.6, with a mean of 198.7,
and estimated planetary A indices were 6, 5, 4, 4, 7, 8 and 4 with a
mean of 5.4.


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