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Issue A&A Volume 367, Number 1, February III 2001 Page(s) 159 - 169 Section Formation, structure and evolution of stars DOI 10.1051/0004-6361:20000402

A&A 367, 159-169 (2001)
DOI: 10.1051/0004-6361:20000402

Magnetocentrifugal acceleration of plasma in a nonaxisymmetric magnetosphere

S. V. Bogovalov

Moscow Engineering Physics Institute, Kashirskoje Shosse 31, Moscow 115409, Russia
    e-mail: bogoval@axpk40.mephi.ru

(Received 28 January 2000 / Accepted 3 November 2000)

Abstract
Violation of the axial symmetry of a magnetic field essentially modifies the physics of the plasma outflow in the magnetosphere of rotating objects. In comparison to the axisymmetric outflow, two new effects appear: more efficient magnetocentrifugal acceleration of the plasma along particular field lines and generation of MHD waves. Here, we use an ideal MHD approximation to study the dynamics of a cold wind in the nonaxisymmetric magnetosphere. We obtain a self-consistent analytical solution of the problem of cold plasma outflow from a slowly rotating star with a slightly nonaxisymmetric magnetic field using perturbation theory. In the axisymmetric (monopole-like) magnetic field, the first term in the expansion of the terminating energy of the plasma in powers of is proportional to , where is the angular velocity of the central source. Violation of the axial symmetry of the magnetic field crucially changes this dependence. The first correction to the energy of the plasma becomes proportional to . Efficient magnetocentrifugal acceleration occurs along the field lines curved initially in the direction of the rotation. I argue that all the necessary conditions for the efficient magnetocentrifugal acceleration of the plasma exist in the radio pulsar magnetosphere. We calculated the first correction of the rotational losses due to the generation of the MHD waves and analysed the plasma acceleration by these waves.

Key words: MHD -- pulsars -- ISM: jets and outflows

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