V. V. Ivanova

The double-gradient magnetic instability: Stabilizing effect of the guide field

The role of the dawn-dusk magnetic field component in stabilizing of the magnetotail flapping oscillations is investigated in the double-gradient model framework (Erkaev et al., Phys. Rev. Lett. 99 ...

Green’s function of compressible Petschek-type magnetic reconnection

We present a method to analyze the wave and shock structures arising from Petschek-type magnetic reconnection. Based on a time-dependent analytical approach developed by Heyn and Semenov [Phys. Plasmas 3, 2725 (1996)] and Semenov et al. [Phys. Plasmas 11, 62 (2004)], we calculate the perturbations caused by a delta function-shaped reconnection electric field, which allows us to achieve a representation of the plasma variables in the form of Green’s functions. Different configurations for the initial conditions are considered. In the case of symmetric, antiparallel magnetic fields and symmetric plasma density, the well-known structure of an Alfven discontinuity, a fast body wave, a slow shock, a slow wave, and a tube wave occurs. In the case of asymmetric, antiparallel magnetic fields, additionally surface waves are found. We also discuss the case of symmetric, antiparallel magnetic fields and asymmetric densities, which leads to a faster propagation in the lower half plane, causing side waves forming a Ma...

Petschek shocks of reconnection for anisotropic pressure

Abstract Many observations show a difference between the pressure parallel and perpendicular to the magnetic field. Thus it is reasonable to study the Petschek reconnection mechanism for the set of equations allowing for pressure anisotropy. We study the simplest case of so—called Petschek shocks, where the Alfven discontinuity and the slow shock degenerate to one discontinuity. More specifically, we consider switch—off shocks, where the magnetic field on the downstream side vanishes in lowest order, so that the plasma is isotropic on that side.

Time-dependent reconnection for anisotropic pressure

An analysis of the reconnection process which extends the famous solution obtained by Petschek for the steady-state case to incorporate the effects of unsteady reconnection in an anisotropic plasma is presented. The case of so-called switch-off shocks, where the Alfven discontinuity and the slow shock degenerate to one discontinuity and the downstream magnetic field vanishes in lowest order, so that the plasma is isotropic in the field reversal region is studied. It is shown that the plasma anisotropy can essentially modify the plasma acceleration, the magnetic field intensity, and the shape of the moving slow shocks. Characteristics of reconnection in several limits, such as the isotropic limit and extreme pressure anisotropy cases corresponding to the fire hose and the mirror instability are analyzed.