Properties of bi-stable mirror mode structures in the magnetosheath

0431020 - ÚFA 2015 US eng A - Abstract
Souček, Jan - Escoubet, C. P.
Properties of bi-stable mirror mode structures in the magnetosheath.
AGU Fall Meeting 2013. San Francisco: AGU, 2013. SM31A-2111.
[AGU Fall Meeting 2013. 09.12.2013-13.12.2013, San Francisco]
Institutional support: RVO:68378289
Keywords : Magnetosheath * Plasma waves and instabilities
Subject RIV: BL - Plasma and Gas Discharge Physics
http://abstractsearch.agu.org/meetings/2013/FM/sections/SM/sessions/SM31A/abstracts/SM31A-2111.html

Magnetosheath mirror mode structures are often observed in the form of non-periodic pressure-balanced low frequency plasma oscillations, characterized by a magnetic field magnitude alternating between two values (high and low field level). This property of fully saturated mirror modes has been previously termed bi-stability in the literature. We performed a statistical study of such events observed by Cluster spacecraft in the magnetosheath an extracted basic parameters of the field oscillations. The dependence of these parameters on global magentosheath context has been investigated as well as the local stability of the observed structures. It is observed that the plasma at the high field level is usually stable or marginally stable with respect to mirror instability, but plasma corresponding to the low field level is unstable. This relationship appears to be a generalization of the previously described association between mirror mode shape and distance to mirror instability threshold. The spatial scale and geometry of the structures has also been investigated and compared to mirror instability theory. It is shown that the areas of low magnetic field level and unstable plasma are usually comparable or smaller than the mirror mode wavelength, which is characteristic of the saturated final stage of the instability development.
Permanent Link: http://hdl.handle.net/11104/0235665