Synchrotron thermal instabilities in extended extragalactic radio sources

The thermal instability of a magnetized plasma produced by the synchrotron emission of relativistic electrons is studied, discussing its possible connection with the filamentary structures observed in the lobes of Cygnus A and in the jet of M87. In addition to the classical thermal condensation mode, it is found that slow magnetosonic waves can be driven unstable. Both modes tend to create structures that are aligned with the background magnetic field. The behavior of the instability is analyzed in different conditions appropriate to the environments under study and the main astrophysical implications are discussed.