Recalling and Updating Research on Diamagnetic Cavities: Experiments, Theory, Simulations

Dan Winske,Ari Le,Christoph Niemann,Joseph D Huba

doi:10.3389/fspas.2018.00051

Abstract

In the decade from the mid 80’s to the mid 90’s there was considerable interest in the generation of diamagnetic cavities produced by the sub-Alfvenic expansion of heavy ions across a background magnetic field. Examples included the AMPTE and CRRES barium releases in the magnetotail and magnetosphere as well as laser experiments at various laboratories in the United States and the Soviet Union. In all of these experiments field-aligned striations and other small-scale structures were produced as the cavities formed. Local and non-local linear theory as well as full particle (PIC), hybrid and Hall-MHD simulations (mostly 2-D) were developed and used to understand at least qualitatively the features of these experiments. Much of this review is a summary of this work, with the addition of some new 3-D PIC and Hall-MHD simulations that clarify old issues associated with the origin and evolution of cavities and their surface features. In the last part of this review we discuss recent extensions of the earlier efforts: new space observations of cavity-like structures as well as new laboratory experiments and calculations with greatly improved diagnostics of cavities formed by expansions of laser-produced ions at super-Alfvenic speeds both across and along the background magnetic field.

Highlights

Many active experiments in space involve the release of canisters of neutral barium atoms
The earlier full particle simulations (Winske, 1988, 1989) of short wavelength flute modes developing on the surface of an expanding debris plasma cloud were carried out in two spatial dimensions perpendicular to the background magnetic field
The physics becomes different as the interaction is dominated by the dynamics of the background plasma as the cavity forms and this interaction determine the cavity size

Summary

INTRODUCTION

Many active experiments in space involve the release of canisters of neutral barium atoms. This photo was taken at about the time that the cloud has reached maximum expansion across the magnetic field and shows fieldaligned striations on the surface of the cloud. Another experiment (Dimonte and Wiley, 1991) employed the two-beam 200 J Janus laser and various target materials at Lawrence Livermore National Laboratory and included a magneto-optic imaging probe (MIP) that was developed and used to obtain accurate measurements of the magnetic field This technique uses Faraday rotation to measure the magnetic field profile continuously in space and time, as shown in the top panels of Figure 2 (Figure 3 in Dimonte and Wiley, 1991). We conclude with a discussion of more recent high-resolution experiments and simulations that have further enhanced our knowledge of the underlying processes

Experiments

Summary

CONCLUSIONS