The K7RA Solar Update

SEATTLE, WA, Apr 7, 2006--I think you'll agree the general trend is
down. An average daily sunspot number of 18.1 for the first quarter
of the year easily compares to the minimum between cycles 22 and
23. From the fourth quarter of 1995 to the second quarter of 1997,
the average daily sunspot numbers for each quarter were 21.3,
13.1, 13, 12.4, 14.2, 11.3 and 25.4. Our recent quarterly average of
18.1 fits right in toward the bottom of the last cycle.

For the near term, expect sunspot numbers and solar flux to decline
gradually. For April 7-13, US Air Force Space Weather Operations
predict a planetary A index of 10, 8, 20, 15, 12, 7 and 5. For the
same period it shows a decline of solar flux values from 100 to 80.
Geophysical Institute Prague predicts quiet to unsettled conditions
on April 7, quiet conditions on April 8, unsettled conditions on April
9, active conditions on April 10, unsettled to active conditions on
April 11, unsettled on April 12, and quiet to unsettled on April 13.
So Prague believes the peak in geomagnetic instability should
occur around April 10, while the US Air Force predicts April 9.

Michael Shelly, WB2KKI, of Pocono Summit, Pennsylvania asks
about MUF charts. These used to appear in QST, and they
showed the predicted change in Maximum Usable Frequency over
a variety of paths--for instance, West Coast USA to Japan--for a
typical 24-hour period based on the month, and the predicted
smoothed sunspot number for the period.

These charts have moved to the ARRL Web site. The page
includes a link to QST articles by Jerry Hall, K1TD, on how to use this tool.

We get mail asking us for more useful information about predicted propagation.
For instance,
when is a good time to work Europe and on what band? This is a good general
question, but the
readers of this report live all over the world, so it is difficult to
generalize. It is even difficult to
make good general statements if we just limit our area of interest to North
America. What is true
for the southern part of the East Coast may not be true for the north, the
Midwest or either end
of the West Coast.

But given data from public sources, you can get some good general custom
projections of
propagation from your location to most other locations on just about any HF
band. Here's how.

First, get some propagation prediction software. A great one is ACE-HF Pro. If
you want free
software, one we've mentioned a lot in the past is W6ELprop. This program works
with either
solar flux or sunspot numbers, but your best bet is probably to use the average
sunspot number
for the past few days, rather than the latest number. These are available at the
Space
Environment Center (SEC) Web site. The latest available data are through April
6.

If I were doing one now, I'd take the average by adding 100, 99 and 99, and
dividing by 3, which
gives us 99.3. If you want to enter the K index into the program, you can get
the mid-latitude
values from WWV, either off the air at 18 minutes after the hour or via the SEC
Web site, which
also provides recent geomagnetic activity.

We depend on the National Oceanic and Atmospheric Administration's Space
Environment
Center for our main source of data. The SEC jointly operates the Space Weather
Operations
Center with the US Air Force and serves as the national and world warning center
for
disturbances that can affect people and equipment on Earth and in space. Funding
for these
services in the administration's 2007 budget had been expected to stay at
current levels, but it
now appears that severe cuts may be on the horizon. I've posted some information
about this on
the Web.

For more information concerning propagation and an explanation of the numbers
used in this
bulletin see the ARRL Technical Information Service Propagation page. An archive
of past
bulletins is on the ARRL Web site.

Sunspot numbers for March 30 through April 5 were 35, 39, 39, 68, 79, 62 and 88,
with a mean
of 58.6. The 10.7 cm flux was 83.9, 86.3, 87, 91.1, 100.4, 99.5, and 99, with a
mean of 92.5.
Estimated planetary A indices were 4, 4, 2, 1, 1, 7 and 29, with a mean of 6.9.
Estimated
mid-latitude A indices were 2, 2, 1, 1, 1, 4 and 18, with a mean of 4.1.
(K7RA, ARRL)

dxAce
Michigan
USA