ELEMENTARY THEORY OF NONSTANDARD PROPAGATION 13 
> 
ROUND. 
OR SEA LEVEL My 
DIFFRACTION 
———™ DISTANCE x 
Figure 2. Rays in the standard atmosphere. 
a eee 
3 DIFFRACTION 
REGION 
DISTANCE x 
Ficure 4. Rays with an elevated duct. 
‘phenomena of interest, are presented in Figures 2, 
3, and 4. These figures are plane earth diagrams in 
which the ordinary downward curvature of the earth 
has been eliminated and replaced by an additional 
upward curvature of the rays. On the left-hand side 
of each diagram the M curve is plotted. By equation 
(5) we have 
a=.0, 
if : 
M = M, — 4a.?: 10°. (8) 
The vertical lines drawn on the M curve diagram 
are the values of My — 4 a” - 10® for the rays 
