摘要:

A theory is presented which describes the along-front propagation and cross-front trapping, due to the absorption by multiple critical-layers, of ageostrophic non-divergent perturbations of baroclinic jets. The perturbations are dispersive neutral vorticity waves which use the jet vorticity gradient as a pseudo-β effect.

ISSN:0309-1929    

DOI:10.1080/03091928808208864

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Steepening of relativistic magnetohydrodynamic (MHD) small-amplitude waves is discussed with the nonlinear effects taken into account. First, the propagation properties of the slow, intermediate and fast MHD waves are examined, and then, a condition is derived such that the second of two waves of the same mode launched successively, catches up with the first wave. The condition includes a requirement that ∂(2(w/n2)/∂p2>0, indicating a positive pressure variation of the relativistic compressibility, wherewis the heat function,nis the particle number density andpis the pressure. The same condition is also obtained using the theory of relativistic MHDsimplewaves. Thus, although the intermediate MHD wave does not steepen, the slow and fast MHD waves can steepen owing to the nonlinear effects, producing infinitely large gradients and eventually dissipating after formation of a shock. However, in the extreme-relativistic limit, in which the magnetic energy is much larger than the rest mass plus thermal energy, the steepening rate tends to zero, consistent with relativity.

ISSN:0309-1929    

DOI:10.1080/03091928808208865

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The stability of simple nonlinear α2-dynamos is investigated for cases where the steady problem can be solved exactly. It is found that the only stable nonlinear steady solution is that which bifurcates from the trivial solution at the marginal dynamo number of the most easily excitable linear mode. This result favours magnetic field configurations which possess a definite symmetry with respect to the equatorial plane of cosmic bodies.

ISSN:0309-1929    

DOI:10.1080/03091928808208866

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor