[Aavso-sid-list] Sunrise Effect

[Peter Wilhelm Schnoor]

Dear Fellow Observers,

Apart from that spam today there's not much activity here.

Here's some input:

I've updated my outline charts at:
http://home.arcor.de/df3lp/ ==> "Outline Waterfall-Charts of HBG".

We all know the typical morning traces: at sunrise often a small peak 
can be observed followed by a sharp fall or dip. This rarely happens at 
sunset.

Looking at those outline images I asked myself: Is there a point in 
space where the sun rises just when that sharp border happens each 
morning swinging like a sine wave over the year?

So I wrote a simple Python program including "pyephem" (a Python port of 
the proven "Xephem" algorithms). Then I simulated sunrise at various 
locations between me and the transmitter at various heights and plotted 
it into those overview charts. I defined "sunrise" if the upper limb of 
the sun just passes the horizon - without any (optical) refraction 
effects of the atmosphere.

I think I've found such a point where it fits perfectly: right at the 
midway point at aprox. 55km of height.
See: http://home.arcor.de/df3lp/misc/spec_2008_sun.png

In other words: if the upper limb of the sun passes the horizon at ~55km 
of height in the middle between transmitter and receiver that observed 
sharp fall of field strength occurs at the receiver.
Boundary conditions: 75 KHz, distance ~1000km, propagation path ~S->N.

Any comments?

Merry Christmas & Happy New Year!
Peter Wilhelm Schnoor
54°13.5´N 10°10.2´E