[SADXA] Comments on Gray-line behaviour for the next two weeks - from Bill W7EXG

[W7EXG (Bill)]

To: SADXA
FROM: Bill W7EXG
6/17/16

I had suggested in a 4/5 email, that we had an excellent opportunity to
study the Gray-line effect with the Tucson-Heard propagation. 

As some of you may know, I have been working on a Gray-line study based on
the Tucson / Heard- Island Gray-line observations. While I documented many
of the observations, some of the SADXA members also reported on Date, time
and bearing - which was very helpful and appreciated. 

During last night's SADXA meeting, I mentioned that in the next few weeks,
we are in the middle of one [of two] of most unique Gray-line opportunities
each year.

This is a direct result of this study. 

56% or more of the world is accessible via Gray-line IN ONE DAY, if both
Sunrise and Sunset are taken advantage of, and consideration is given to
both Long Path and Short Path. A good set of Solar Indices for Propagation
would also be helpful!! 

Put simply, and as an example, on 6/21 the Terminator angle at the Equator
is about +/-23 degrees. Since this angle is Latitude dependent, the Tucson
Terminator angle is +/- 32 degrees. 

At Sunset, the Tucson Terminator is + 32 degrees and the Gray-line
Opportunity is +/- 25 degrees about the 32 deg. Terminator. Thus, at Sunset,
you should hear Gray-line propagation between about 7 degrees, and 57
degrees, as well as from 237 deg. to 187 degrees. 

At Sunrise, the Tucson Terminator is - 32 degrees and the Gray-line
Opportunity is +/- 25 degrees about the -32 deg. Terminator. Thus, at
Sunrise, you should hear Gray-line propagation between about 303 degrees,
and 253 degrees, as well as from 123 deg to 173 degrees.

The magic +/- 25 degrees can be a bit of a variable, but it is based on the
duration of the Heard Signals observed, when in the DAY regions. This
defined the DAY distance the signals were from Terminator (and distance of D
Layer and Critical E Freq from DAY Terminator). 

40m through 20m is likely, and 80m and 17m is possible. Again, solar indices
are critical - Low Kp / A and high SFI is good.  Be aware of flares - some
can cause increase in MUF without increasing the DAY D and E absorption and
without increasing the Critical E layer Frequency. Otherwise, they can be a
detriment, so say the least. 

I can say more about time-lines, but in general listen a few hours before
Sunset/Sunrise, and conditions could list several hours after
Sunset/Sunrise. This time line can be a variable, since the time-line is
also a strong function of the MUF in the Signal Paths (SP or LP) which also
is time variant.  

I have sampled Europe and ZL signals at the most recent Sunset, and E Asia
sigs at the most recent sunrise. 

All of this info was generated in my report as mentioned above. 

Report is entitled:
Gray-line Propagation: Lessons Learned from the Tucson / Heard-Island
Experience. 

I plan to send report to a few of the Contributors for review, prior to any
presentation on this matter. 

Some aspects, such as ionization in the Dark Region of the F layer at
Sunrise have been declared as a Myth in some recent presentations and QST
publications. 

While in the overall scheme of Gary-line, this discussion is
inconsequential, it will be clearly shown this Myth is a MYTH, based on
recent and not so recent research data published in research journals. There
is nothing like data, to stop all the arm waving. 

Good Luck and Have FUN with Gray-line in the next few weeks. 

73s, 

Bill W7EXG