ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension a, transverse to the confining magnetic field, is comparable to the ion sound gyroradius cs/Ωi, where cs is the sound speed and Ωi the ion cyclotron frequency. The radial structure of the wave azimuthal magnetic field is found to consist of four regions: a Bessel function behavior for r〈a, a near null at r≅a, and a driven Airy pattern for r(very-much-greater-than)a which merges onto the 1/r asymptotic region. The pattern spreads at an angle given by tan θ=(ω/Ωi)(cs/vA)/2.6, where ω is the modulation frequency and vA is the Alfvén speed. This behavior arises because there is a maximum value at finite k⊥ for the ratio of the perpendicular to parallel group velocity, which differs from the cone spreading [G. J. Morales et al., Phys. Plasmas 1, 3765 (1994)] associated with inertial Alfvén waves. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.872531
