Dynamics of fluxons in a system of coupled Josephson junctions

Different dynamical processes with fluxons are analyzed in the framework of a known model describing two weakly coupled long Josephson junctions. It is demonstrated that two colliding fluxons belonging to different junctions can form a bound state due to energy dissipative losses. Collision between a fast fluxon and a large-amplitude (low-frequency) breather (bound fluxon-antifluxon state) belonging to different junctions is considered too, and a threshold condition for the possibility of breaking the breather into the fluxon-antifluxon pair is found. Some radiative effects are investigated. The equilibrium velocity of the fluxons motion in the case when this velocity exceeds the limit velocity of the mate junction is found with regard to the Cherenkov energy losses. Then radiative effects accompanying collision of two fluxons are considered for the cases when the fluxons belong either to the same or to different junctions. For both cases the total emitted energy and its spectral distribution are obtained.