Electron pairing in mirror modes: Surpassing the quasilinear limit


The mirror mode evolving in collisionless magnetised high-temperature thermally anisotropic plasmas is shown to develop an interesting macro-state. Starting as a classical zero frequency ion fluid instability it saturates quasi-linearly at very low magnetic level, while forming extended magnetic bubbles which trap the electron component. The electrons perform an adiabatic bounce motion along the magnetic field which might cause a bulk electron anisotropy resulting in an electron mirror mode, which was identified in simulations and spacecraft data. Further evolution of the mirror mode towards a stationary state is determined by the trapped bouncing electrons. They interact with the thermal level of ion sound waves generating attractive wake potentials and form pairs in the lowest-energy singlet state of two combined electrons. This process takes preferentially place near electron mirror points where the pairs become spatially locked with all their energy in the gyration. The resulting coherent diamagnetic surface current causes an orbital diamagnetism which cancels a fraction of the magnetic flux of the initial quasi-linearly stable mirror mode. Pressure balance allows estimating the limitation of the mirror amplitude, which for the magnetosheath is in reasonable numerical agreement with observation.

Further Information
  author = {Treumann, R. A. and Baumjohann, W.},
  journal = {Ann. Geophys.},
  language = {en},
  note = {accessible in the Discussion forum at https://doi.org/10.5194/angeo-2019-86},
  pages = {971},
  title = {Electron pairing in mirror modes: Surpassing the quasilinear limit},
  url = {https://doi.org/10.5194/angeo-2019-971},
  volume = {37},
  year = {2019},
%O Journal Article
%A Treumann, R. A.
%A Baumjohann, W.
%J Ann. Geophys.
%G en
%O accessible in the Discussion forum at https://doi.org/10.5194/angeo-2019-86
%P 971
%T Electron pairing in mirror modes: Surpassing the quasilinear limit
%U https://doi.org/10.5194/angeo-2019-971
%V 37
%D 2019