Determination of a macro- to micro-scale progression leading to a magnetized plasma disruption

Abstract

We report observations of a plasma jet evolving through a macro-to micro-scale progression sequence. This leads to a fast magnetic reconnection that results in the jet breaking o from its originating electrode and forming a force-free state. A sausage-like pinching occurs rst and squeezes an initially fat, short magnetized jet so that it becomes thin. The thin jet then becomes kink unstable. The lengthening of the jet by the kinking thins the jet even more since the kink is an incompressible instability. When the jet radius becomes comparable to the ion-skin depth, Hall and electron inertial physics become important and establish the environment for fast magnetic reconnection. This fast reconnection occurs, disrupting the jet and establishing a force-free state. X-ray bursts and whistler waves, evidence of magnetic reconnection, are observed when the plasma jet breaks o from the electrode. This experimentally observed sequence of successive thinning from pinching followed by kinking is reproduced in a three-dimensional ideal MHD numerical simulation. The results of the experiment and the numerical simulation together demonstrate a viable path from macro-scale MHD physics to micro-scale non-MHD physics where fast reconnection occurs.

Caltech Lab Experiments and the Insights They Provide Into Solar Corona Phenomena

“…By operating the experiment in a somewhat different regime, choking of the flux rope cross section down to d i was observed by Seo et al. (2020) without the intermediate process of the kink driving a RTI. Here instead, the kink instability directly caused the flux rope cross section to be reduced to be of the order of d i .…”

“…Seo et al. (2020) observed this process in the coaxial configuration and saw that the aspect ratio (i.e., length/radius) of a flux rope increased as the flux rope underwent kink instability and that when the radius decreased to be of the order d i , an X‐ray burst, a whistler wave burst, and a change of magnetic topology (magnetic reconnection) occurred simultaneously. The X‐ray burst is indicative of the sudden development of a large inductive electric field and is consistent with localized interruption of current because of localized increase in resistivity.…”

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

“…Burch et al, 2016;Torbert et al, 2018;Chen et al, 2020;Hesse and Cassak, 2020) and laboratory experiments (e.g. Dong et al, 2012;Gekelman et al, 2016;Olson et al, 2016;Howes, 2018;Takahata, Yanai, and Inomoto, 2019;Seo et al, 2020), such studies will advance our fundamental understanding of the energetics of solar and astrophysical reconnection, determining how the energy is partitioned between bulk flows and random motions, between plasma acceleration and heating (Ji and Daughton, 2011;Coates, 2016;Yamada, Yoo, and Myers, 2016).…”

Features of transport induced by ion-driven trapped-electron modes in tokamak plasmas

“…In the previous experimental and numerical researches, the results demonstrate a viable path from macro-scale MHD physics to microscale non-MHD physics associated with the occurrence of fast reconnection. [9] In the last decade, the increasement of interest in the interaction between turbulence and MHD phenomena has occurred in the fusion device plasmas, both experimentally and theoretically. [10,11] The sawtooth and neoclassical tearing modes (NTMs) essentially dominate the core MHD activity.…”