FluxSurface Average Operator
The fluxsurface average operator,
, is defined [8]

(8.67) 
where
and
.
It follows that

(8.68) 
for any
. It is helpful to define

(8.69) 
It follows that

(8.70) 
for any
.
Equation (8.66) yields

(8.71) 
where
is an undetermined fluxsurface function.