Polarization as a probe of magnetic field and plasma properties of compact radio sources - Simulation of relativistic jets

Abstract

view Abstract Citations (120) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Polarization as a Probe of magnetic Fields and Plasma Properties of Compact Radio Sources: Simulation of Relativistic Jets Jones, T. W. Abstract The relationship between linearly and circularly polarized synchrotron emission and the internal magnetic field and plasma properties of compact radio sources is explored through a large set of numerical simulations. The simulations involve approximate, divergent jet flows of relativistic plasma and turbulent magnetic fields. The numerical results in most cases can be expressed approximately in analytical forms based on simple physical insight. These results are compared to the observed properties of compact jets. The most severe constraint which results comes from the small observed values of circular polarization. Tight limits seem called for on the relativistic electron distribution. These limits require the energy distribution to peak very close to the energy of observed radiating electrons. Within the context of relatively smooth flows this applies to both normal plasma sources and those composed of electron-positron pairs and would exclude large Faraday depths. In a broader context it is pointed out that integrated polarization measurements alone do not really allow a clear distinction between sources composed of normal plasma and those composed of pairs, nor do they allow a unique measure of the presence or absence of internal Faraday rotation. However, VLBI polarization observations in all four Stokes parameters may be able to resolve these ambiguities. Inclusion of circular polarization in these observations will be very important. Jet structures consisting of distinct, bounded zones (i.e., distinct components) may be more consistent with the integrated polarization constraints than are smoothly varying structures. The significance of circular polarization comes from the strong tendency of inhomogeneous sources to generate circular polarization from linear polarization. This is true even when Faraday rotation is absent. The influence of shock compression of the tangled magnetic field was also explored. The strong tendency of transverse shock features in compact jets to depolarize due to Faraday rotation is pointed out. Especially when observed with VLBI, shocks may provide important diagnostics of the source plasma. Publication: The Astrophysical Journal Pub Date: September 1988 DOI: 10.1086/166685 Bibcode: 1988ApJ...332..678J Keywords: Extragalactic Radio Sources; Polarized Electromagnetic Radiation; Radio Jets (Astronomy); Relativistic Plasmas; Computerized Simulation; Plasma Jets; Synchrotron Radiation; Very Long Base Interferometry; Astrophysics; GALAXIES: JETS; POLARIZATION; RADIATION MECHANISMS full text sources ADS | data products SIMBAD (3) NED (3)