Magnetic energy dissipation via reconnective relaxation in astrophysical jets

The magnetic energy release through field-line reconnection is considered for a force-free jet which expands (or contracts) radially in response to variations in the confining external pressure. The main new result obtained in comparison with previous publications on the subject, where this mechanism has been proposed, is that a self-consistent theory for the reconnective relaxation of the jet's magnetic configuration has been constructed. It enables us to calculate the magnetic energy dissipation rate inside a jet for an arbitrary value of the ratio τ_r/τ_v, where τ_r is a typical reconnection time and τ_v is the expansion time. Thus these results provide a well-grounded support to the conclusion that this magnetic energy dissipation mechanism could, in principle, power the observed radio emission in extragalactic jets. Moreover, knowing the observed radiation power (and, hence, the required energy supply) it is possible to obtain information about the value of τ_r, which enters in the theory as a phenomenological parameter.