Date/Time
Date(s) - 02/03/2022
1:55 pm - 2:55 pm
Location
Rhines 125
Categories
Byonghoon Seo, Ph.D.
Assistant Professor
Embry-Riddle Aeronautical University
Dr. Byonghoon Seo
Ph.D., 2014, Korea Advanced Institute of Science and Technology (KAIST)
Postdoc, 2014-2016, Korea Research Institute of Standards and Science
Postdoc, 2016-2019, California Institute of Technology
Assistant Researcher, 2019-2020, UCLA Basic Plasma Science Facility
Assistant Professor, 2020- present, Embry-Riddle Aeronautical University, Physical Sciences
Abstract
An MHD-driven magnetized jet experiment injects a plasma flow with embedded magnetic helicity into a large vacuum chamber to investigate astrophysical jets, spheromak formation, controlled thermonuclear fusion, and magnetic reconnection. Regimes of the 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 jet impacting a target cloud in regime (I) in the magnetized inertial fusion context. It was 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. The experiment was performed at the Caltech spheromak experiment