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Astron. Astrophys. 336, 209-219 (1998)

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Natural polarization modes in pulsar magnetospheres

A. von Hoensbroech 1, 2, H. Lesch 2 and T. Kunzl 2, 3

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
2 Institut für Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, D-81679 München, Germany
3 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85740 Garching, Germany

Received 11 March 1998 / Accepted 28 April 1998


We present a comprehensive investigation of the radio polarization properties within the theory of natural electromagnetic wave modes in pulsar magnetospheres. Taking into account the curvature of the field lines, aberration effects and magnetic sweep-back we use the relativistic dielectric tensor in the low-density cold plasma approximation and derive the following polarization characteristics, which are in full agreement with the observational findings. Specifically, we demonstrate that 1. The degree of linear polarization decreases with increasing frequency. 2. The degree of circular polarization increases with increasing frequency. 3. At high frequencies ([FORMULA] a few GHz) the degree of linear polarization is correlated to the spin down luminosity [FORMULA]. 4. At high frequencies long-period pulsars exhibit weaker linear polarization than their short-period counterparts. 5. The difference between the refractive indices of the two natural wave modes decreases with increasing frequency which possibly results into a depolarization via superposition.

Key words: plasmas – polarization – radiative transfer – waves – stars: pulsars: general

Send offprint requests to: A. von Hoensbroech, (avh@mpifr-bonn.mpg.de)

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998