Analytical description of the flux-flow mode in a long Josephson junction

The flux-flow mode in a long one-dimensional Josephson junction is studied analytically. An approximate steady-state solution of the perturbed sine-Gordon equation is derived in the form of a dense fluxon chain accompanied by small-amplitude plasma waves. Next, some time-averaged quantities are calculated, making it possible to evaluate the constant bias current and the constant voltage between the junction electrodes. The analytical results are compared with numerical simulations both for the field distribution within the junction and for the I-V characteristics. [S0163-1829(99)12533-5].