dxAce wrote in message ...
bpnjensen wrote:

dxAce wrote in message ...

snips

No, the grey line is not always necessarily a straight line path, but can be a
'crooked path', and that is 'veering around corners' as you say.

Hmmm - can you explain this?

Geometrically, with the sun's rays essentially parallel to one another
shining on the disc of the earth, the grayline would always represent
a virtually perfect circumference, no matter which exact face the
earth presents to the sun - hence, while a flat map of the world shows
an undulating wave, the grayline is actually a 'straight' line along
the earth's face. The only deviation from this that I can determine
would be the astronomical width of the sun, about 0.5 degree, and
whatever 'ionic' width either side of that partial illumination at
sunrise/sunset would be involved in improved propagation.

I can imagine that something about the earth's magnetic field could
vary this, especilly *at* the poles - is this why some 'crookedness'
can occur?

Thanks,
Bruce Jensen