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ARRL Propagation Bulletin ARLP040 (2001)

ARLP040 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7VVV
Seattle, WA  September 28, 2001
To all radio amateurs 

ARLP040 Propagation de K7VVV

This has been an incredible week for solar activity. Your author was
out of town over the weekend, and on Monday received an email from
WM7D, titled "New High?". It read: "The SFI is 279."

Indeed this was a new solar flux high for this sunspot cycle, and it
rose even higher two days later when it hit 282.6. The previous high
solar flux was 273.5 on March 28, 2001, and before that was 262 on
May 17, 2000. The high activity at the end of March and during this
week would seem to shift the peak of the solar cycle forward, but
that reading is always based on a smoothed running average, and is
determined long after the peak.

The determination of the peak is influenced by high daily values on
many days around the period of peak activity, not just on one day of
high numbers. But the high activity this week is not isolated. The
trends have been solidly higher for two months.

By the way, WM7D has a nice web site with lots of solar and
propagation information. Find it at Click on the
Solar Resource Page, and from there find many links to various
charts and images. Don't miss the "More Solar Information Links" at
the bottom of that page.

Average daily solar flux rose dramatically this week from last, by
nearly 45 points. Average daily sunspot numbers were up nearly 90

With all the new sunspots and associated energy radiating from the
sun, there were some geomagnetic upsets also. The worst days were
Sunday and Wednesday, when the planetary A index was 27 and 24.
Sunday had a rapid rise in geomagnetic indices, starting out the UTC
day with the planetary K index at 0, then going to 5 only six hours

The most recent projection shows geomagnetic indices stabilizing
briefly with a planetary A index of 10 on Friday, then rising to 15
on Saturday and 18 on Sunday. Projected solar flux is 265 for Friday
and 260 for both Saturday and Sunday.

Since we have just passed the autumnal equinox, the fall DX season
is in full effect. Now is a great time to enjoy the best propagation
in years on 12 and 10 meters, which should peak over the next month
or two. Of course all of this high solar activity also tends to
bring geomagnetic disturbances and associated absorption, especially
on high latitude paths. But when you hear the K index on WWV
reported at 3 or lower, that is when conditions should be great.

Sunspot numbers for September 20 through 26 were 276, 258, 293, 275,
315, 320 and 278 with a mean of 287.9. 10.7 cm flux was 226.8,
238.6, 255.2, 258.5, 279.3, 275.1 and 282.6, with a mean of 259.4,
and estimated planetary A indices were 5, 5, 10, 27, 6, 18 and 24
with a mean of 13.6.


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