アイテム詳細

要旨

Current sheets (CSs) are widespread objects in space plasma capable of storing and, then, explosively releasing the accumulated magnetic energy. In planetary magnetotails the cross-tail CS plays an important role in the global dynamics of the tail and in the transformation of the magnetic energy into the kinetic and thermal energies of the ambient plasma. We have analyzed 114 crossings of the cross-tail CS by the MAVEN spacecraft at X _MSO ~ [-1.0, -2.8]R _M. Magnetic field observations with high time resolution allowed the observation of the inner superthin CS (STCS) with a half-thickness L _STCS ~ (1-100)ρ _e (ρ _e is the gyroradius of thermal electrons) in 75 intervals of the CS crossings from our database. The STCS was embedded into a thicker ion-scale CS and provides 10%-50% of the total current density in the cross-tail CS. Our analysis has shown that the observed L _STCS and the embedding parameter, σ _emb, characterizing the contribution of the STCS to the total current density in the CS are well described by the novel analytical kinetic model of a multilayered CS with an inner embedded electron-scale layer: L _STCS~ (0.9-1.2)λ and σ _emb ~ (0.9-1.2) σ _model, where the universal spatial scaling λ ~ δ _i ²/ρ _P and the embedding parameter σ _model ~ δ _i /ρ _P are determined by the local ion inertial length (δ _i ) and gyroradius of thermal protons (ρ _P ) in the STCS.