2017/02/28 by E. E. Nokhrina, Elena Nokhrina
Physics and Astronomy · #Amplitude #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Brightness #Brightness temperature #Computational physics #Electron temperature #Equipartition theorem #Gamma-ray bursts and supernovae #Magnetic energy #Magnetic field #Magnetization #Magnetohydrodynamics #Physics #Plasma #Quantum mechanics #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stx521
published as MNRAS (2017), 468(2), 2372-2381 · 10 pages; accepated for publication in MNRAS
arxiv created 2017/02/28 · openalex publication_date 2017/02/28 · openalex created_date 2017/03/16 · arxiv updated 2017/04/17 · openalex updated_date 2026/08/05
The limit on the intrinsic brightness temperature, attributed to ‘Compton catastrophe’, has been established being 1012 K. Somewhat lower limit of the order of 1011.5 K is implied if we assume that the radiating plasma is in equipartition with the magnetic field – the idea that explained why the observed cores of active galactic nuclei (AGNs) sustained the limit lower than the ‘Compton catastrophe’. Recent observations with unprecedented high resolution by the RadioAstron have revealed systematic exceed in the observed brightness temperature. We propose means of estimating the degree of the non-equipartition regime in AGN cores. Coupled with the core-shift measurements, the method allows us to independently estimate the magnetic field strength and the particle number density at the core. We show that the ratio of magnetic energy to radiating plasma energy is of the order of 10−5, which means the flow in the core is dominated by the particle energy. We show that the magnetic field obtained by the brightness temperature measurements may be underestimated. We propose for the relativistic jets with small viewing angles the non-uniform magnetohydrodynamic model and obtain the expression for the magnetic field amplitude about two orders higher than that for the uniform model. These magnetic field amplitudes are consistent with the limiting magnetic field suggested by the ‘magnetically arrested disc’ model.