The Parker Instability in the Interstellar Medium

摘要: We review the elementary formalism and basic physics of instability in a galactic disk first two dimensions (defined by vertical component gravitational field essentially horizontal interstellar magnetic field). Then we discuss how nature changes presence three-dimensional perturbations spatially varying field. “Final” equilibrium states are obtained dimensions, reachable from Parker’s stratified initial state through continuous deformations lines. process inherently open system magnetohydrostatic equations is closed self-consistent fashion. The represent giant clouds (or cloud complexes) valleys variation calculated column density along spiral arms agreement with observations. An energy integral for an isothermal plasma also discussed. Finally calculations which have recently followed numerically nonlinear evolution instability. Work questions significance medium or attributes to unattainable consequences reviewed critically.