Topic: "The Physics of Laboratory Magnetosphere" (Video)
Abstract: During the past decade, we have developed the laboratory magnetosphere as a research tool for the study of high-temperature and high-beta plasma confined in near steady-state conditions. Laboratory magnetospheres exhibit fascinating and highly complex collective dynamics, and they provide outstanding access for detailed measurement of interchange mixing, turbulent fluctuations, and convective transport. While space physics has motivated our investigations, the devices we study are not intended to be scaled magnetospheres. The large scale circulation and the global dynamics found in planetary magnetospheres are driven by the solar wind and magnetic reconnection events. In the laboratory, by comparison, we control the properties of the plasma and turbulent mixing by adjusting internal microwave heating sources and gas fueling levels. Th geometric characteristics of the dipole field have important consequences: (i) plasma can be stable with local beta exceeding unity, (ii) fluctuations can drive either heat or particles inward to create stationary profiles that are strongly peaked, and (iii) the absence of magnetic shear can decouple particle and energy confinement. Past experiments and modeling efforts with laboratory magnetospheres have lead to new understanding of interchange, centrifugal and entropy modes, nonlinear gyrokinetics, and plasma transport. Two devices, the LDX experiment at MIT and the RT-1 experiment at the University of Tokyo, operate with levitated superconducting dipole magnets. With a levitated dipole, not only is very high-beta plasma confined in steady state but, also, levitation produces high-temperature at low input power and demonstrates that toroidal magnetic confinement of plasma does not require a toroidal field. Modeling has explained many of the processes operative in these experiments, including the observation of a strong inward particle pinch. Our most recent work includes: observation of the dynamical structures generated in turbulence, measurement of the self-consistent response of the turbulent pinch due to changing power and fueling, and describing plasma self-organization from electrostatic turbulence.