Experimental study of mini-magnetosphere

TL;DR

This study presents laboratory experiments on mini-magnetospheres, revealing detailed magnetic structures and currents, supporting a two-fluid Hall effect model, and filling gaps in space observation data.

Contribution

First laboratory demonstration of mini-magnetosphere magnetic structures and currents, validating the two-fluid Hall effect model with detailed magnetic field measurements.

Findings

Non-coplanar magnetic field component is independent of dipole reversal.

Distinct lobes and current sheet observed in the tail region.

Tail-ward electric current matches ion current, indicating stationary electrons.

Abstract

Magnetosphere at ion kinetic scales, or mini-magnetosphere, possesses unusual features as predicted by numerical simulations. However, there are practically no data on the subject from space observations and the data which are available are far too incomplete. In the present work we describe results of laboratory experiment on interaction of plasma flow with magnetic dipole with parameters such that ion inertia length is smaller than a size of observed magnetosphere. A detailed structure of non-coplanar or out-of-plane component of magnetic field has been obtained in meridian plane. Independence of this component on dipole moment reversal, as was reported in previous work, has been verified. In the tail distinct lobes and central current sheet have been observed. It was found that lobe regions adjacent to boundary layer are dominated by non-coplanar component of magnetic field. Tail-ward oriented electric current in plasma associated with that component appears to be equal to ion current in the frontal part of magnetosphere and in the tail current sheet implying that electrons are stationary in those regions while ions flow by. Obtained data strongly support the proposed model of mini-magnetosphere based on two-fluid effects as described by the Hall term.