Register Account

Login Help

ARRL Propagation Bulletin ARLP010 (2005)

ARLP010 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7RA
Seattle, WA  March 11, 2005
To all radio amateurs 

ARLP010 Propagation de K7RA

The sun was quiet this week, but a new chain of sunspots is rotating
into a geo-effective position. There were some active days for
geomagnetic conditions, most pronounced on March 6-8, and due to a
solar wind stream. The average daily planetary A index rose less
than 11 points to 20.1, and the average mid latitude A index rose
less than 6 points to 12.3. Average daily sunspot numbers were up
over 21 points to 36.1, and average daily solar flux rose less than
10 points to 85.9

Rising solar flux and increasing sunspots are expected over the next
week. Solar flux should peak around March 15-16 near 115, then drop
below 100 around March 20. The most active predicted geomagnetic day
in the near term is March 14, but conditions should be merely
unsettled, rather than stormy.

Enjoy the next few weeks. The period around the equinox, the change
from winter to spring is a good time for HF propagation, even with
the sunspot count so low.

With a cry of "Say it isn't so!" Vince Varnas, W7FA of Aloha, Oregon
sent an article claiming that the next solar cycle, set to begin in
a few years, may turn out to have the weakest maximum of any cycle
in the past 100 years. He sent the article as an attachment, but I
found it online at,
If that link is troublesome, try a cached version at

Let's hope the next one, Cycle 24, proves this forecasting method
wrong. We don't see many solar cycles in our lifetimes, not to
mention our time as amateur radio operators. I was lucky to start
early at age 12, 40 years ago this month, and am in my 4th solar
cycle. I was just young enough to have missed cycle 19, the grandest
of them all, which peaked after the middle of the last century in
the late 1950s.

Alex Mendelsohn, AI2Q of Kennebunk, Maine sent in a link to an
interesting article from the Air Force Research Laboratory magazine
about an all-sky imager that detects solar plasma clouds. You can
read it at
Even better, check out Alex's own radio room and some very
impressive homebrew projects on his personal web site at

If you would like to comment or have a tip, email the author at,

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at,

Sunspot numbers for March 3 through 9 were 24, 13, 22, 22, 43, 52
and 77 with a mean of 36.1. 10.7 cm flux was 77, 78.9, 81.2, 83.6,
87, 93.5 and 99.9, with a mean of 85.9. Estimated planetary A
indices were 4, 3, 10, 36, 42, 26 and 20 with a mean of 20.1.
Estimated mid-latitude A indices were 2, 1, 8, 17, 28, 17 and 13,
with a mean of 12.3.


Instragram     Facebook     Twitter     YouTube     LinkedIn