Electronic Resource
[S.l.]
:
American Institute of Physics (AIP)
Physics of Plasmas
2 (1995), S. 3857-3864
ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The linearized incompressible magnetohydrodynamic equations that include a generalized Ohm's law are solved for tearing eigenmodes of a plasma sheet with a normal magnetic field (Bn). In contrast to the Harris sheet with the equilibrium magnetic field [B=B0 tanh(z/a)xˆ], the two-dimensional plasma sheet with the field [B=B0 tanh(z/a)xˆ+Bnzˆ], in which the Bn field lies in the plane of the Bx field, has no neutral line if Bn≠0. Such a geometry is intrinsically resilient to tearing because it cannot change topology by means of linear perturbations. This qualitative geometrical idea is supported by calculations of growth rates using a generalized Ohm's law that includes collisional resistivity and finite electron inertia as the mechanisms for breaking field lines. The presence of Bn reduces the resistive tearing mode growth rate by several orders of magnitude (assuming Bn/B0∼0.1) compared with that in the Harris sheet model (Bn=0). The growth rate scaling with Lundquist number (S) has the typical S−3/5 (S−1/3) dependence for large (small) wave numbers and very small values of Bn. For larger values of Bn, all modes behave diffusively, scaling as S−1. The collisionless electron tearing mode growth rate is found to be proportional to δ2e in the presence of significant Bn((approximately-greater-than)10−2B0) and large kx(∼0.1a−1–0.5a−1), and becomes completely stable (γ〈0) for Bn/B0≥0.2. Implications for magnetospheric substorms are discussed. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.871085
Permalink
|
Location |
Call Number |
Expected |
Availability |