Issue |
A&A
Volume 445, Number 3, January III 2006
|
|
---|---|---|
Page(s) | 779 - 794 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20053040 | |
Published online | 03 January 2006 |
Radio pulsar drifting sub-pulses and diocotron instability
1
Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands e-mail: fung@astro.uu.nl
2
Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
3
Centre for Plasma Astrophysics, K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium; on leave for Institute of Astronomy, University of Zielena Góra, Lubuska 2, 65-265, Zielena Góra, Poland / Astrophysical Observatory, Al. Kazbegi ave. 2a, Tbilisi 0160, Georgia
Received:
10
March
2005
Accepted:
12
July
2005
The potential
role of a diocotron instability in causing drifting sub-pulses in
radio pulsar emission is investigated for aligned magnetic
rotators. It is assumed that the out-flowing plasma above a pulsar
polar cap consists of an initially axially symmetric, hollow beam
of relativistic electron positron pair plasma which carries an
electric charge as well as a current. The occurrence of
instability depends on shear in the angular velocity distribution
of the beam as a function of axial distance. Instability occurs
under typical pulsar conditions at mode numbers 40. It
destroys the symmetry of the equilibrium configuration and leads
to a carousel of density columns which rotates at fixed angular
pattern speed. The process is applied to two pulsars with observed
carousels of drifting sub-pulses, and the diocotron instability at
corresponding mode number and axial distance is used as a
diagnostic for the charge and current density of the polar flow.
Key words: stars: pulsars: general / plasmas / magnetohydrodynamics (MHD) / instabilities
© ESO, 2006
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