ARRL

ARRL Propagation Bulletin ARLP010 (2002)

SB PROP @ ARL $ARLP010
ARLP010 Propagation de K7VVV

ZCZC AP10
QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7VVV
Seattle, WA  March 8, 2002
To all radio amateurs 

SB PROP ARL ARLP010
ARLP010 Propagation de K7VVV

Sunspot numbers are down, and the sun is relatively quiet, although
there has been a solar wind stimulating some geomagnetic activity
this week. Average sunspot numbers dropped nearly 16 points this
week over last, and average solar flux was down over 14 points.
Geomagnetic planetary A indices moved out of the single digits this
week, and averaged about double last week's average.

The most active day was February 28th, with planetary K indices as
high as 5. Contesters were grateful that conditions quieted down
for the ARRL Phone DX Contest last weekend. There was also some
geomagnetic activity on March 5-6, when the K index over several
periods was 4.

The sun should be quiet over the next week, with solar flux below
200.

The first day of spring is less than two weeks away. The equinox is
a great time for HF propagation. 10-meters should be good over the
next few weeks, and 15-meters will improve as we move later into
spring.

K9LA writes in to report that subtraction and multiplication were
not his high point last week. Here's the correct version of the data
he reported.

The monthly median critical frequency foF2 at Dyess AFB (Abilene,
Texas) for December 2000 was 11.65 MHz. For December 2001, it was
13.2 MHz. That's a difference of 1.55 MHz, and is representative of
the increased worldwide ionization in December 2001.

With the F2 region MUF for a 3000 km path being about 3 times the
critical frequency, that 1.55 MHz difference in critical frequencies
translates to a MUF roughly 5 MHz higher in December 2001 than
December 2000. This increase was due to the recent resurgence in
Cycle 23, and goes a long way in explaining why December 2001 (and
the months around it) were so good for 6-meters compared to a year
ago.

Sunspot numbers for February 28 through March 6 were 188, 153, 153,
169, 197, 168 and 191 with a mean of 174.1. 10.7 cm flux was 204.2,
187.7, 191, 182.7, 174.9, 172.2 and 177.8, with a mean of 184.4, and
estimated planetary A indices were 17, 11, 5, 10, 9, 15 and 15 with
a mean of 11.7.
NNNN
/EX