Stability of MHD shear flows: Application to space physics

摘要: Shear slows of magnetised plasmas are routinely observed in the solar atmosphere, planetary magnetospheres, and interplanetary space. They also ubiquitous elements models remote astrophysical objects like interacting stellar winds binary systems. Studying stability such flows is paramount for understanding physical processes The simplest shear flow a tangential magnetohydrodynamic (MHD) discontinuity. We start our review from considering instability MHD discontinuity (called Kelvin-Helmholtz (KH) instability) first incompressible plasmas, then taking compressibility into account. introduce notion absolute convective instabilities. behaviour absolutely unstable qualitatively different that convectively flows. instabilities based on analysis asymptotic (for large time) solution initial value problem. problem ill-posed: increment unbounded. This implies discontinuities cannot be studied. To obtain well-posed we have either to take dissipation account, or consider continuous velocity profile. In both cases surprising result: account these two effects decreases threshold jump needed instability. phenomenon related negative energy waves. show that, cases, so-called rather than KH Finally examples theory application: heliopause Earth's magnetopause.