‰ Now 18 WPM transition file follows ‰

This week saw sunspot numbers and solar flux decline.  Average daily
sunspot numbers declined from 199.3 to 138.7, while solar flux
dropped from 162.9 to 149.7.  Sharp eyed readers may notice that we
reported average daily sunspot numbers last week at 202.4, not
199.3, but we just noticed a discrepancy between what last weeks
bulletin reported for March 4 and 5 and what we see now from NOAA.
I dont know if NOAA revised the sunspot numbers for those days, or
we just made a mistake, but instead of sunspot numbers of 171 and
202 on March 4 and 5, they were actually 160 and 191.  This brings
the average sunspot number for that week down from 202.4 to 199.3
Also in question is the mid latitude A index on March 12, reported
as 3.  I totally made that number up, guessing because something
interfered with collection of data from the Fredericksburg, Virginia
station from around 1500 UTC on March 12 until 2100 UTC on March 13.
The first four K index readings on March 12 came in at 2, 0, 1 and 2
and the last three readings on March 13 at 2, 0 and 3.  The A index
for the day is calculated from the eight K index measurements.  The
most recent prediction has solar flux at 145 on March 14 and 15, 140
on March 16 to 20, 135 on March 21 and 22, then 145, 150 and 145 on
March 23 to 25, 140 on March 26 and 27, 135 on March 28 and 29, then
130, 125 and 120 on March 30 through April 1, 115 on April 2 to 4,
and 110 on April 5 to 7.  Flux values would then rise to a high of
140 on April 20, which is not very high, but that is a long way out,
more than seven weeks away.  Predicted planetary A index is 5 on
March 14 to 16, 8 on March 17 and 18, 5 on March 19 to 29, 8 on
March 30 through April 1, 5 on April 2 to 5, and then 12, 10 and 8
on April 6 to 8, then back to 5 again until April 26.  OK1HH sends
us his weekly geomagnetic forecast from the Czech Republic, on
behalf of the Czech Propagation Interest Group.  He and OK1MGW began
doing these in 1978.  The geomagnetic field will be quiet to
unsettled March 14 and 15, mostly quiet March 16 and 17, quiet to
active March 18 and 19, active to disturbed March 20, quiet to
active March 21, quiet to unsettled March 22, quiet March 23 and 24,
quiet to active March 25, quiet March 26, quiet to active March 27,
mostly quiet March 28 to 31, quiet April 1 and 2, quiet to unsettled
April 3, active to disturbed April 4, and quiet to active April 5.
Space.com has an interesting article about a great geomagnetic
disturbance and aurora 25 years ago in March, 1989.  Note the spring
equinox will be here in just a few days.  The first day of spring is
Thursday, March 20, and the equinox occurs at 1657 UTC.  Both the
southern and northern hemispheres will be bathed in equal measures
of solar radiation.  The equinox is a great time for HF propagation.
For more information concerning radio propagation, see the ARRL
Technical Information Service at //arrl.org/propagation of rf
signals.  For an explanation of the numbers used in this bulletin,
see //arrl.org/the sun the earth the ionosphere.  An archive of past
propagation bulletins is at //arrl.org/w1aw bulletins archive
propagation.  More good information and tutorials on propagation are
at //k9la.us/.  Monthly propagation charts between four USA regions
and twelve overseas locations are at //arrl.org/propagation.
Sunspot numbers were 174, 161, 138, 123, 122, 108, and 145, with a
mean of 138.7.  10.7 cm flux was 148.8, 148.2, 141.6, 145.9, 151.5,
164.6, and 147.6, with a mean of 149.7.  Estimated planetary A
indices were 6, 4, 4, 3, 6, 4, and 6, with a mean of 4.7.
Estimated mid latitude A indices were 5, 3, 5, 2, 4, 4, and 3, with
a mean of 3.7.

‰ End of 18 WPM transition file ‰