ARRL

ARRL Propagation Bulletin ARLP008 (2005)

SB PROP @ ARL $ARLP008
ARLP008 Propagation de K7RA

ZCZC AP08
QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7RA
Seattle, WA  February 25, 2005
To all radio amateurs 

SB PROP ARL ARLP008
ARLP008 Propagation de K7RA

Average daily geomagnetic indices for the week were slightly higher,
and the average daily sunspot numbers and solar flux were down
markedly. Average daily sunspot numbers were down nearly 30 points
to 45.4, and average daily solar flux was down nearly 19 points to
97.3. This is compared to the seven days reported at the end of last
week's Propagation Forecast Bulletin ARLP007.

A week ago this bulletin mentioned that conditions for last
weekend's ARRL International DX CW Contest should be fair to good,
but there was a worry about geomagnetic activity. Mid-latitude
geomagnetic activity wasn't bad, but polar paths were affected more.
The planetary A index for February 18-20 was 25, 14 and 12, and the
high latitude college A index (from Alaska) was 37, 40 and 16. The
mid latitude A index was moderate, at 14, 8 and 6.

Jeff Hartley, N8II in West Virginia mentioned in an email that he
had a blast on 20-meters, despite the somewhat disturbed conditions.
The beam heading from his place to Japan is 330 degrees, which puts
it right through the auroral zone. JA stations were weak and
fluttery. Propagation to Europe was much better (Germany has a 47
degree beam heading for Jeff), and he worked about 1500 European
stations.

Disturbed conditions on HF often portend good propagation on VHF.
Jon Jones, N0JK of Kansas mentioned Sporadic E skip on 6-meters from
February 18-23. He and Ken Neubeck, WB2AMU are working on a paper on
the subject of geomagnetic disturbances and 6-meter E-layer
propagation. Jon writes, "While aurora activity usually dampens
regular mid-latitude Es, the day(s) after the aurora subsides may
see increased Es activity." WB2AMU has written extensively on VHF,
and has published the books, "Six Meters-A Guide to the Magic Band"
and "VHF Propagation-A practical guide for radio amateurs."

N0JK mentioned that the February 20th 6-meter opening lasted from
1900z to 0100z, and extended across much of the eastern states and
southern Canada. He worked two stations in Mexico that day, and
wrote, "From Kansas, stations in Georgia and Florida were booming in
for hours." He noted that E-layer openings in late February are
rare.

This weekend is the CQ World Wide 160-Meter SSB Contest, and for
160-meters we hope for quiet geomagnetic conditions. The latest
forecast for February 25-27 is for a planetary A index of 15, 20 and
20. The Prague Geophysical Institute projects active geomagnetic
conditions for February 26, and unsettled to active for February 25
and 27. This is because earth is moving into a solar wind stream
coming from a coronal hole. Sunspot numbers and solar flux should
remain quite low. Predicted solar flux for February 25-27 is 80, and
flux values are not expected to rise above 100 until around March 9,
and then only slightly.

If you would like to comment or have a tip, email the author at,
k7ra@arrl.net.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,
http://www.arrl.org/tis/info/propagation.html.

Sunspot numbers for February 17 through 23 were 51, 46, 51, 60, 33,
23 and 54 with a mean of 45.4. 10.7 cm flux was 111.3, 104.2, 98.5,
95.7, 94.5, 92.3 and 84.6, with a mean of 97.3. Estimated planetary
A indices were 6, 25, 14, 12, 8, 4 and 4 with a mean of 10.4.
Estimated mid-latitude A indices were 7, 14, 8, 6, 4, 3 and 2, with
a mean of 6.3.
NNNN
/EX