Spontaneous formation of knots in relativistic flows - A model for variability in compact synchrotron sources
Abstract
A model is proposed in which regions of enhanced synchrotron emission are formed via radiative thermal instabilities in relativistic flows. A perturbed volume in which the magnetic field is enhanced by a few tens of a percent relative to the steady value collapses due to the increased cooling rate and consequent loss in pressure. The collapse further increases the magnetic field, leading to even shorter radiative lifetimes. The instability progresses in this way until either the external electron pressure is balanced by the perturbed magnetic pressure or the overall expansion of the flow becomes important. A fluid-dynamical treatment of the instability is performed, and the results are shown to apply to flux variations and formation of knots in the relativistic flows which are thought to occur in quasars and active galactic nuclei. The knots possess the same kinematic properties as the collimated flow and can thus be responsible for the apparent superluminal motions observed in compact radio sources.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1980
- DOI:
- 10.1086/158110
- Bibcode:
- 1980ApJ...239..296M
- Keywords:
-
- Astronomical Models;
- Magnetohydrodynamic Flow;
- Radio Sources (Astronomy);
- Relativity;
- Synchrotron Radiation;
- Thermal Instability;
- Active Galactic Nuclei;
- Quasars;
- Radiative Lifetime;
- Spontaneous Emission;
- Very Long Base Interferometry;
- Astrophysics