Abstract
Abstract. We examine the physics of the magnetic mirror mode in its final state of
saturation, the thermodynamic equilibrium, to demonstrate that the mirror
mode is the analogue of a superconducting effect in a classical
anisotropic-pressure space plasma. Two different spatial scales are
identified which control the behaviour of its evolution. These are the ion
inertial scale λim(τ) based on the excess density
Nm(τ) generated in the mirror mode, and the Debye scale
λD(τ). The Debye length plays the role of the correlation length
in superconductivity. Their dependence on the temperature ratio
τ=T‖/T⟂<1 is given, with T⟂ the reference temperature
at the critical magnetic field. The mirror-mode equilibrium structure under
saturation is determined by the Landau–Ginzburg ratio
κD=λim/λD, or
κρ=λim/ρ, depending on whether the Debye length
or the thermal-ion gyroradius ρ – or possibly also an undefined
turbulent correlation length ℓturb – serve as correlation
lengths. Since in all space plasmas κD≫1, plasmas with λD
as the relevant correlation length always behave like type II
superconductors, naturally giving rise to chains of local depletions of the
magnetic field of the kind observed in the mirror mode. In this way they
would provide the plasma with a short-scale magnetic bubble texture. The
problem becomes more subtle when ρ is taken as correlation length. In
this case the evolution of mirror modes is more restricted. Their existence
as chains or trains of larger-scale mirror bubbles implies that another
threshold, VA>υ⟂th, is exceeded. Finally,
in case the correlation length ℓturb instead results from
low-frequency magnetic/magnetohydrodynamic turbulence, the observation of
mirror bubbles and the measurement of their spatial scales sets an upper
limit on the turbulent correlation length. This might be important in the
study of magnetic turbulence in plasmas.
Subject
Space and Planetary Science,Earth and Planetary Sciences (miscellaneous),Atmospheric Science,Geology,Astronomy and Astrophysics
Cited by
5 articles.
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