Complex astrophysical experiments relating to jets, solar loops, and water ice dusty plasma

Abstract

Recent results of three astrophysically relevant experiments at Caltech are summarized. In the first experiment magnetohydrodynamically driven plasma jets simulate astrophysical jets that undergo a kink instability. Lateral acceleration of the kinking jet spawns a Rayleigh-Taylor instability, which in turn spawns a magnetic reconnection. Particle heating and a burst of waves are observed in association with the reconnection. The second experiment uses a slightly different setup to produce an expanding arched plasma loop which is similar to a solar corona loop. It is shown that the plasma in this loop results from jets originating from the electrodes. The possibility of a transition from slow to fast expansion as a result of the expanding loop breaking free of an externally imposed strapping magnetic field is investigated. The third and completely different experiment creates a weakly ionized plasma with liquid nitrogen cooled electrodes. Water vapour injected into this plasma forms water ice grains that in general are ellipsoidal and not spheroidal. The water ice grains can become quite long (up to several hundred microns) and self-organize so that they are evenly spaced and vertically aligned.

The dynamics of supersonic plasma flow interaction with the magnetic arch

“…Under experimental conditions, the thermal pressure in the plasma flow is much less than the ram pressure ρv 0 2 =n i m i v 0 2 . Thus, the ratio between plasma flow pressure and magnetic pressure can be defined as b p = n m v B 8 i i 0 2 2 . The β-ratio is changing in a wide range of --10 10 2 3 with respect to different positions in the vacuum chamber.…”

“…Laboratory study of the interaction of supersonic flows of strongly ionized plasma with magnetic fields of the arched configuration is relevant for understanding the physical mechanisms of a number of space plasma phenomena observed in the inner regions of the coronal loops on the Sun [1][2][3], in the transition regions of planetary magnetospheres [4,5], such as, boundary layers of the Earth's magnetosphere and the planets of the solar system.…”

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

“…During the initial year of the campaign in 2017, experiments observed whistler waves driven by runaway electrons, relevant to the physics of the Van Allen radiation belts. 423 Laboratory experiments also contribute to the investigation of other aspects of space and planetary environments beyond the physics of plasmas, including the study of the physics of ice under the cryogenic vacuum conditions of space, 424,425 investigation the formation of ice in dusty plasma environments, 347,348 the ablation of micrometeoroids in Earth's atmosphere, 426 the effect of micrometeoroid impact on icy surfaces, 427 and the determination of the surface chemistry of planets and moons, such as Titan. [428][429][430] Viewed collectively as a national resource for the laboratory investigation of the physics of space plasmas, akin to the collection of spacecraft missions that comprise the Heliophysics System Observatory, these facilities have the capability the contribute uniquely to progress in our understanding of space physics.…”