2008ApJ...679.1000T

In active galaxies, minimum energy estimates based on the observed radio emission suggest that 10% or more of the total gravitational energy released by the collapse of a supermassive black hole is deposited into lobe-scale magnetic fields and relativistic particles, roughly in equipartition. It is proposed here that the underlying physical process inside the lobe is magnetic self-organization by driven relaxation, rather than a traditional magnetohydrodynamic dynamo. There are two forms of magnetic self-organization. The extreme form of Taylor relaxation is similar to a driven harmonic oscillator, in which a resonance in spatial frequency constrains the input magnetic energy and helicity to the lowest order relaxation mode, commonly known as a spheromak in laboratory plasmas. The general form of magnetic self-organization takes into account the intrinsic nonlinearity of a driven plasma, which can access relaxed states beyond the spheromak resonance. This is a particularly useful physics description for radio lobe plasmas, which are likely overdriven. The degrees of self-organization can be quantified by a spectral energy analysis over the spatial distribution of the magnetic field. The preferred self-organized states can be characterized by a principal component analysis using a projection onto the fundamental relaxation modes that are unique to a given radio lobe morphology.