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

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 laserproduced ions at super-Alfvenic speeds both across and along the background magnetic field.

AMBITION – comet nucleus cryogenic sample return

“…With an expanding coma, neutral densities are higher at comets for a given level of collisionality, which makes measurements easier. Comparing the nature of the diamagnetic cavity present in different levels of collisionality and magnetisation (e.g., at comets, after supernovae explosion, or in laser experiments, [201]) is of high relevance to different communities.…”

Astrophysical Explosions Revisited: Collisionless Coupling of Debris to Magnetized Plasma

“…In this section, we perform 2D simulations similar to those of Section 4, but now with the magnetic field perpendicular to the simulation plane. While this geometry does not track the parallel dispersion of the expanding plasma cloud, it captures flute‐like interchange modes (Colgate, 1965; Dyal, 2006; Huba et al., 1987; Ripin et al., 1987; Winske et al., 2019; Zakharov et al., 2006) that allow the transport of plasma across the magnetic field. The flute modes captured by the hybrid model are modified Rayleigh‐Taylor modes driven by the deceleration of the debris cloud, and they do not include smaller‐scale lower hybrid drift modes.…”

“…. 2D simulations with the magnetic field perpendicular to the plane allow the development of flute modes as the debris decelerates against the background (Colgate, 1965;Sgro et al, 1989;Winske, 1988;Winske et al, 2019). An additional dimensional effect is that the transport caused by flute modes is exaggerated in 2D simulations.…”

Experiments With Plasmas Artificially Injected Into Near-Earth Space

“…The CRRES results (Huba et al, 1992) confirmed the predictions, however, skidding times and distances turned out to be lower than calculated, namely 3 s and 9 km for a 10 kg release. Further discussions on the current state of skidding theory and experiment can be found in a review paper by Winske et al (2019).…”