
80 HIGH POWER MICROWAVES
• X-Mode
kc
22
22
22
=
−
−
−
−
ωω
ωω
UH
(3.33)
with
ωω
±
=+
±
1
4
22
12
ce pe ce
/
(3.34)
ωωω
UH
2
pe
2
ce
2
(3.35)
To demonstrate the relationship between the dispersion relations (3.32) and (3.33) and the ECRH
frequency requirements, we consider rst the O-mode waves with the dispersion relation 3.32.
There are some frequencies for which there are no real solutions for the wavenumber k; speci-
cally, for frequencies below the plasma frequency, k is imaginary. The implication is that waves
at those frequencies exponentially diminish in magnitude with distance into the plasma (causality
rules out the growing wave solution ...