‰ Now 18 WPM transition file follows ‰


After five days of no sunspots from May 24 to 28, spots returned on
May 29, and have increased since in number and size.  There are
currently several sunspots visible, and the sunspot number for the
past five days, Sunday through Thursday, was 58, 58, 63, 47 and 59.
Coupled with quiet and stable geomagnetic indicators, this is good
for HF propagation.  Our reporting week for this bulletin, with the
numbers reported at the end, runs from Thursday through Wednesday,
and the average daily sunspot number for May 31 to June 6 rose
nearly 43 points to 46R1 when compared to the prior seven days.
Average daily solar flux rose nearly 15 points to 83R7.  Last weeks
Propagation Forecast Bulletin ARLP023 mentioned ARRL Field Day, now
just two weeks away.  The bulletin reported, in some uncorrected
versions, that the event is always held on the last full weekend in
June, but Don Jackson, AE5K of Marion County, Arkansas pointed out
that the rules specify the fourth full weekend.  Both fourth and
last are on the same weekend this year, or June 23 and 24, which is
usually the case, but not always.  In 2002, the fourth full weekend
was June 22 and 23, but the last full weekend was June 29 and 30.
This occurs whenever June 1 is a Saturday, as it will be again in
2013 and 2024.  Last week the latest projection looked like no
sunspots around Field Day with a declining geomagnetic disturbance,
but this week the forecast looks a little better.  Including the
Friday before, the event doesnt begin until Saturday, the projected
solar flux last week for June 22 to 24 was 65 for all three days,
with a planetary A index of 20, 12 and 5.  This weeks prediction for
those dates shows the same A index, but a solar flux 10 points
higher, at 75 for all three days.  A check of recent sunspot numbers
alongside solar flux values on the same dates, which can be seen on
the sec.noaa.gov web site, shows no sunspots when the solar flux was
down around 65, but at 75 the sunspot number can be in the 40s.  For
the next few days expect continued quiet geomagnetic activity, with
the same moderate, for the low point of the sunspot cycle, sunspot
count.  Alex Mendelsohn, AI2Q in Kennebunk, Maine sent a link to an
article about a solar burst last December 6, which caused problems
for GPS receivers.  You can read it on the tinyurl.com web site.
See how we reported the same flare in ARLP051 in 2006.  Our bulletin
shows that the solar flux observatory in British Columbia also had
problems from that event.  Sunspot numbers were 11, 41, 45, 58, 58,
63 and 47 with a mean of 46R1. 10R7 cm flux was 74R6, 79R4, 83R2,
87, 85R7, 88R8, and 87R1, with a mean of 83R7. Estimated planetary A
indices were 4, 6, 7, 10, 8, 3 and 2 with a mean of 5R7. Estimated
mid latitude A indices were 2, 5, 5, 7, 8, 2 and 2, with a mean of
4R4‚

‰ End of 18 WPM transition file ‰