We saw
that the retarded 15 wave-extrapolation equation
is like the heat-flow equation with the exception that
the heat conductivity must be replaced
by the purely imaginary number *i*.
The amplification factor
(the magnitude of the factor in parentheses in equation (71)) is now the square root of the sum squared of real
and imaginary parts.
Since the real part is already one, the amplification factor exceeds unity
for all nonzero values of *k ^{2}*.
The resulting instability is manifested by the growth of dipping plane
waves.
The more dip, the faster the growth.
Furthermore, discretizing the

10/31/1997