"MHD-driven plasma jets relevant to thermonuclear fusion, MHD instability, and magnetic reconnection," by Byonghoon Seo (Caltech)

Thursday, May 16, 2019 - 12:30pm to 1:30pm
Plasma Seminars

The Caltech jet experiment injects a plasma with embedded magnetic helicity into a large vacuum chamber to investigate astrophysical jets, spheromak formation, controlled thermonuclear fusion, and magnetic reconnection. Regimes of the Caltech plasma jets are classified based on a twist parameter called λ as follows: regime (I) has low values of λ resulting in a stable, straight plasma jet, regime (II) has intermediate λ involving a kink instability, and regime (III) has high λ. Regime (I) and (III) are the subject of this talk. I will be giving a talk about compression and heating of an MHD-driven plasma jets impacting a target cloud in regime (I) in the magnetized inertial fusion context. It is revealed from the experimental results that significant radiative loss occurs when the jet is compressed. Criteria for how fast the compression must be to outrun the radiative loss is provided. Then, in regime (III), I will be presenting the sausage to kink current-driven instability mode transition that results in fast magnetic reconnection. Modern theories postulate that cascades of MHD modes should be fundamental to solar and astrophysical plasma dynamics. We have observed such a cascade: an MHD sausage instability leads to an MHD kink instability which leads to the kink self-thinning and so causing a fast magnetic reconnection with associated hard X-ray and whistler wave bursts. The observed cascade has been reproduced in a 3D numerical simulation and the cascade parameter-space trajectory agrees with the predictions of MHD stability theory.

Event Attachments: 
BaPSF Auditorium, Rehab Building Room 15-70