Advance Knowledge and Understanding of Multi-Scale Phenomena in a Real Plasma

California Institute Of Technology, Pasadena CA

Investigators

Abstract

This award enables continuation of an experimental exploration of eruptive plasma behavior in a laboratory under conditions similar to those on the sun and in other astrophysical objects. While laboratory plasmas have a much shorter lifetime than the solar and astrophysical plasmas, namely microseconds compared to anywhere from hours to millions of years for astrophysical plasmas, they can model many of the same phenomena in a reproducible and controllable fashion allowing for detailed studies. The present effort will focus on the study of the observed X-ray generation in a magnetized relatively cold plasma, under conditions when such high energy emission is not generally expected. This study has relevance to solar flares which similarly produce X-rays and very energetic particles that can damage spacecraft, and, in extreme cases, are associated with electric power grids disruptions. The project will also continue to engage a local high school with a vast majority of students from under-represented minority groups, motivating interest in science and encouraging them to pursue careers in plasma physics or other science and engineering fields. The ongoing research program is focused on determining how a seemingly benign, cold, collisional plasma can suddenly erupt and generate a burst of energetic particles, extreme ultra-violet radiation, hard X-rays, and high-frequency waves. In doing so, it contributes to the goals of NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" program. The knowledge and understanding being gained apply to many astrophysical and laboratory plasmas, such as solar flares, astrophysical gamma ray bursts, X-ray bursts from terrestrial lightning, and dense plasma foci devices. The program employs a well-diagnosed laboratory device in which reproducible arched magnetized plasma structures in the shape of coronal loops are formed and then exhibit kink and Rayleigh-Taylor magnetohydrodynamic (MHD) instabilities. A sequence of these instabilities pushes the plasma to a regime where the MHD approximation fails and non-MHD phenomena develop. This failure occurs when the electron velocity distribution becomes sufficiently non-thermal, with a significant population of highly energetic electrons leading to the generation of X-ray bursts. The continued investigation of these phenomena will employ high-speed visible and X-ray movie cameras, polarimetry to measure magnetic fields, and direct detection of energetic electrons. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.