A&A 411, 203-213 (2003)
DOI: 10.1051/0004-6361:20031239

Cross-field charge transport by the diocotron instability in pulsar magnetospheres with gaps

J. Pétri¹, J. Heyvaerts¹ and S. Bonazzola<sup>2

1</sup>  Observatoire de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
²  DARC, Observatoire de Meudon, place Jules Jansen, 92195 Meudon, France

(Received 28 June 2002 / Accepted 30 July 2003 )

Abstract
In a previous work, we have shown by linear analysis that a thin charged disk in differential rotation in the magnetosphere of a neutron star with vacuum gaps is unstable to a collisionless instability induced in non-neutral plasmas by differential rotation, the diocotron instability. In this paper we study the long-time-scale evolution of this instability in the non-linear regime by means of both direct numerical simulations and a quasilinear model. We show that, when the disk is externally fed with charged particles produced by a moderate pair creation activity in the magnetosphere, the diocotron instability causes diffusion of the charged particles across the magnetic field lines outwards. An equatorial cross-field electric current is observed to form, carrying a net charge flux radially outwards. This constitutes a hitherto ignored charge transport mechanism in the pulsar magnetosphere. We briefly discuss how this turbulent charge transport mechanism could bear on the problem of electric current closure in pulsar's magnetospheres.

Key words: stars: pulsars: general -- plasmas -- magnetohydrodynamics (MHD) -- methods: numerical

Offprint request: J. Pétri, petri@newb6.u-strasbg.fr

© ESO 2003

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