RECONNECTIVE RELEASE OF MAGNETIC ENERGY IN ASTROPHYSICAL PLASMAS

Two particular examples are considered of astrophysical objects contai ning a highly conducting tenuous plasma with an excess magnetic energy supplied by an external source. The first example is the solar corona , whose magnetic field is continuously distorted by footpoint shufflin g due to photospheric motions. The second case is an extragalactic jet extending from a galactic nucleus with an immersed magnetic field, an d which is perturbed by variations in the pressure of the external med ium. In both cases it is assumed that the system tends towards its low est magnetic energy equilibrium via magnetic reconnection, thus provid ing a fast release of injected magnetic energy. Explicit relations bet ween the characteristics of the external driver and the magnetic energ y dissipation rate in these objects have been obtained. The relevance of this mechanism for heating the solar corona and maintaining radio e mission from extragalactic jets is then discussed by comparing these r esults with observational data.