ARRL

ARRL Propagation Bulletin ARLP047 (2004)

SB PROP @ ARL $ARLP047
ARLP047 Propagation de K7RA

ZCZC AP47
QST de W1AW  
Propagation Forecast Bulletin 47  ARLP047
From Tad Cook, K7RA
Seattle, WA  November 19, 2004
To all radio amateurs 

SB PROP ARL ARLP047
ARLP047 Propagation de K7RA

Conditions calmed over the past week, with average daily sunspot
numbers lower by over 35 points and average daily solar flux down
over 28 points. November 11 and 12 were the last days with high
geomagnetic activity, caused by intense solar wind streams which
buffeted the earth recently. Currently those active areas of the sun
are transiting our star's far side. Just two days ago a large
sunspot, probably 693, was seen on the other side of the sun with a
technique known as helioseismic holography. For more information on
this method, see the web site,
http://soi.stanford.edu/data/farside/index.html and
http://soi.stanford.edu/press/ssu03-00/backside.html.

This weekend is the ARRL November SSB Sweepstakes. There is a
possibility of aurora, but probably only at higher latitudes,
nothing like recent sightings of northern lights as far south as
Arizona. The predicted planetary A index for November 19-22 is 5,
12, 15 and 10. Predicted solar flux for the same period is 100,
rising to 110 around November 22 and 120 the next day. Solar flux
should peak for the near term near 135 around November 26-28.

Chip Margelli, K7JA, who wrote in last week's bulleting about aurora
propagation wrote back to say he got a big overheated in all the
excitement, and wrote heliopause when he meant to say Harang
Discontinuity.

Chip writes:

"Either side of the Harang Discontinuity seems to have some very
dynamic possibilities during extreme geomagnetic events like we just
experienced. Around the Harang Discontinuity, you get very
interesting propagation shifts, between AU-E and straight E or F2
propagation. This would account, I believe, for the rapidly-changing
reports of signal quality, especially from Northern California
(where one guy would report KH6SX solid, direct path, with no AU
sound, and five minutes later someone would report heavy aurora
distortion and a more northerly path)."

If you are wondering like I was what a Harang Discontinuity could
be, check out the web sites,
http://www.oulu.fi/~spaceweb/textbook/harang.html,
http://www.agu.org/pubs/crossref/1991.../90JA02344.shtml and
http://www.faculty.uaf.edu/ffjrk/dipolarization.html.

In some late aurora news, Lefty Clement, K1TOL in Turner, Maine said
he had a tremendous thrill on November 7 when he worked OZ4VV and
MM0AMW on 6 meters. This is only the third time in 30 years on 6
meters that he has worked Europe via Auroral-E skip without the
assistance of the F2 layer. The OZ QSO was his furthest yet. He was
also hearing European commercial television signals S9, and heard
via a European chat cluster that G4IGO and an SM6 heard him for a
five minute period.

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 November 11 through 17 were 70, 52, 50, 69, 57,
46 and 59 with a mean of 57.6. 10.7 cm flux was 94.9, 97.4, 96.4,
100.3, 105.6, 108.4 and 104.9, with a mean of 101.1. Estimated
planetary A indices were 23, 30, 8, 9, 3, 8 and 6, with a mean of
12.4. Estimated mid-latitude A indices were 22, 23, 7, 7, 2, 5 and
7, with a mean of 10.4.
NNNN
/EX