On Fri, 19 Mar 2010, Paul Nicholson wrote:
> Given
> 
>   B = sqrt( 9.5e-21 * ERP/r) * exp( -r/a)
> 
> where a = 2.9e6 for daytime path, or 4.3e6 for nighttime
> path, day and night charts are plotted here,
> 
>   http://abelian.org/vlf/prop9-day.png
>   http://abelian.org/vlf/prop9-night.png

Paul, parameter 'a' may be essentually larger if signal propagated over
salt water.  It depends on deposit of ionosphere and ground to
attenuation. Thus nice theoretical problem arises. We can rather easy
evaluate parameter 'a' without dissipation in ionosphere (describing it as
perfect conductor). Then we can compare this value with empirical value.
If such 'ideal ionosphere' value is close to empirical value then ground
yelds main part of attenuation. In this case salt water gives much larger
parameter 'a' and stronger signal then expected. Othervise main part of
attenuation is ionosphere attenuation and 'a' over the water is close (up
to small corrections) to 'a' over ground. I'll solve this problem but few
weeks latter. Now i should live my home for work and have no time.

Regards,
Alexander