Linear Polarization of Radiation from Oblique and Conical Shocks
Abstract
A simple model for synchrotron radio emission from oblique and conical shock waves is described, and the polarization properties are examined assuming that the magnetic field in plasma upstream from the shock is random in direction. Such structures have been suggested as the origin of radio emission from the knots in radio jets that emerge from active nuclei, particularly on VLBI scales. It is found that conical shock waves in jets of circular cross section can yield polarized radiation with electric vector either parallel or perpendicular to the jet axis. In cases that yield perpendicular electric vectors the degree of polarization (for this model) does not exceed 10%. The results provide insight into the extent to which conical shock waves might account for the polarization structures of jets in BL Lac objects and quasars that have been revealed by recent VLBI polarimetry. The relationship between polarization and kinematics for jets in which weak oblique shocks occur at large apparent bends is also considered.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1990
- DOI:
- 10.1086/168409
- Bibcode:
- 1990ApJ...350..536C
- Keywords:
-
- Linear Polarization;
- Magnetohydrodynamics;
- Oblique Shock Waves;
- Radio Jets (Astronomy);
- Synchrotron Radiation;
- Active Galactic Nuclei;
- Bl Lacertae Objects;
- Bow Waves;
- Magnetic Field Configurations;
- Relativistic Plasmas;
- Astrophysics;
- BL LACERTAE OBJECTS;
- GALAXIES: JETS;
- POLARIZATION;
- QUASARS;
- RADIATION MECHANISMS;
- SHOCK WAVES