Radiation Field and Q of a Resonant Cylindrical Plasma Column

A cylindrical plasma column displays a series of resonant responses when it is excited by an electromagnetic wave with its electric field and direction of propagation both perpendicular to the axis of the column. In the principal member of the mode spectrum, the electrons are taken to move in phase in a direction transverse to the axis of the column. The diameter of the column is small compared to wavelength. In this paper, for the transverse electronic motion described, an expression for the vector potential in the region about the column is derived and thence the electromagnetic field components. The radiation field components E φ and Hz vary as ρ−½. The effect of radiation damping is calculated by deriving an expression for the selectivity factor Q. The expression is Q = (λ/a)2/2π3, when the radius a is much less than a wavelength.