ARRL

ARRL Propagation Bulletin ARLP014 (2008)

SB PROP @ ARL $ARLP014
ARLP014 Propagation de K7RA

ZCZC AP14
QST de W1AW  
Propagation Forecast Bulletin 14  ARLP014
From Tad Cook, K7RA
Seattle, WA  March 28, 2008
To all radio amateurs 

SB PROP ARL ARLP014
ARLP014 Propagation de K7RA

It is exciting to see heightened solar activity one week into
Spring.  Currently three sunspots are visible, 987, 988 and 989, and
the consensus says that all seem to be old Cycle 23 spots.  But with
the three sunspot groups so close to the Sun's equator, it is hard
to tell for certain.  We know that Cycle 24 spots should have
magnetic polarity opposing the magnetic signature of Cycle 23
sunspots, but this is also true for sunspots below the equator
relative to sunspots above.

Average sunspot numbers for the reporting week (Thursday through
Wednesday) rose over 18 points from the previous week, to 23.4.
Average daily solar flux was up nearly six points to 75.4.  Average
geomagnetic indicators were unchanged, but this is because they fell
from the start of last week, and rose this week.

An M2-class solar flare erupted from sunspot 989 on March 25, but it
was not earth-directed.  Even so, it stimulated geomagnetic activity
over the following two days.  The mid-latitude K index peaked at
five, early (UTC) on March 27, which was Wednesday evening in North
America.  The high latitude College K index (Fairbanks, Alaska)
peaked earlier from 0900-1500 UTC on March 26 at a level of six.
This was 1:00-7:00 AM Alaska Daylight Time on Wednesday.

The short term forecast is for sunspot activity around where it has
been for the past few days, possibly extending to the end of the
first week in April.  The predicted planetary A index for March 28
through April 7 is 15, 10, 10, 5, 8, 5, 5, 15, 25, 15 and 10.

Geophysical Institute Prague predicts unsettled to active conditions
for March 28, unsettled March 29-30, quiet to unsettled March 31
through April 1, and quiet conditions April 2-3.

Expect improved conditions for the CQ World Wide WPX SSB Contest
this weekend.

With the VHF discussions in this bulletin over the past few weeks,
John Adams, K4JYX of Port Orange, Florida wanted to remind us about
ducting.  About ten years ago he was on 2 meter FM in Daytona Beach
when he tuned across a full-quieting signal from a repeater he
sensed couldn't be local.  The conversation he monitored mentioned
downtown Cleveland, and he was trying to think of a Cleveland
outside of Ohio he might be hearing, but Cleveland Tennessee was too
far away.  John broke in, mentioned he was in Daytona, which the
other operators thought was Dayton.  John was running 25 watts into
a vertical, and the conversation continued with strong signals.

John writes, "We carried on for about 35 minutes, and suddenly they
disappeared, never to be heard from again.  I checked the weather
channel, and a front had just passed - a front that had extended up
through Cleveland, Ohio.  The signals apparently entered the
temperature inverted front and were ducted as if in a physical duct,
the 1600 miles or so between us.  Freak QSOs are fun!"

Jon Jones, N0JK responded to JE1BMJ's comments attributing
long-distance 6 meter propagation to Polar Mesosphere Summer Echo.
Jon published a paper in the 2007 Central States VHF Society
Proceedings analyzing JA to USA and Europe multi-hop openings in
2006.  Jon says the propagation was, "multi-hop sporadic E. Some of
the Es hops may have been 'Es cloud to Es cloud' in addition to
'ground - Es cloud - ground.' The path loss may have been reduced by
Es hops over salt water. The footprints via Multi-hop Es can 'focus'
at times to relatively small areas."

Some 10 meter reports arrived this week.  Joaquin Montoya, EA2CCG
reports from Northern Spain that on Friday, March 21, 10 meter
signals from South America were quite strong. He mentioned Argentina
and Brazil coming in at S7-9, and a friend of his worked a Brazilian
with just an antenna on his balcony.

Terry Oldham, KH6MT of Grand Island, Florida notes that on Thursday,
March 27 he is hearing Hawaii stations on 10 meters.

Carl Luetzelschwab, K9LA mentioned that in our last bulletin the
claim was made that at the equinox, "all of the earth is receiving a
maximum amount of solar radiation, the same in both southern and
northern hemispheres."  He pointed out that this is not really the
case, as the Sun's output is constant, for all practical purposes.

Carl wrote, "At the equinoxes both hemispheres are illuminated
equally, i.e., the angles of incidence of solar radiation on the
atmosphere in both hemispheres are similar. In the northern
hemisphere Summer, the angle of incidence is closest to
perpendicular, providing the highest residual nighttime MUFs."

He continues, "One would thus think that Summer daytime MUFs would
also be higher, but another process comes into play to alter that --
the ratio of atomic oxygen (important for electron production) to
molecular oxygen and molecular nitrogen (important for electron
loss) is higher in Winter than in Summer, resulting in higher
daytime MUFs in the Winter. This is the so-called F2 region winter
anomaly."

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

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at,
http://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin see,
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.  Monthly
propagation charts between four USA regions and twelve overseas
locations are at http://www.arrl.org/qst/propcharts/.

Sunspot numbers for March 20 through 26 were 0, 0, 0, 14, 35, 52,
and 63 with a mean of 23.4.  10.7 cm flux was 68.4, 68.2, 69.6, 72,
79.4, 88.6, and 81.6 with a mean of 75.4.  Estimated planetary A
indices were 8, 5, 5, 8, 4, 4 and 27 with a mean of 8.7.  Estimated
mid-latitude A indices were 7, 4, 4, 7, 2, 3 and 16, with a mean of
6.1.
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/EX