Reconstruction of Mirror Structures in the Magnetosheath Observed by MMS Spacecraft

Mirror structures are a by-product of mirror-mode instability in the collisionless plasma with pressure anisotropy of p⊥ > p||. The subscripts 1 and || denote the components perpendicular and parallel to the local magnetic field. Mirror structures are of a compressible magnetic field structure, in which the magnetic field strength is anti-correlated with the plasma density. A two-dimensional reconstruction technique is recently developed successfully to recover steady, magnetohydrostatic coherent structures with pressure anisotropy, using magnetic field and plasma data from a single spacecraft. This paper presented reconstruction maps of mirror structures in the Earth’s magnetosheath observed by the Magnetospheric Multiscale (MMS) spacecraft. A series of magnetic bottle-like structures was recovered, and its invariant axis was nearly perpendicular to the average magnetic field. The width of the magnetic trough was ~2000 km, while the separation between two troughs within the same flux tube was ~8000 km. The mirror structures were more or less aligned with the average magnetic field projected on the reconstruction plane.