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Physics

 

Spring 2006 Physics Seminar Series

Seminars are held on Fridays at 3:00 pm in McCook Auditorium; Refreshments start at 2:45


Self-organization in Magnetized Plasmas

M. Brown
Dept. of Physics and Astronomy Swarthmore College

hydra cluster
image source:  plasma.physics.swarthmore.edu

It is a common process in the universe for plasma and magnetic fields to evolve together in a turbulent way but then rapidly relax to simple, self-organized structures. Solar flares erupt from the photosphere tangled and chaotic, but via a process called magnetic reconnection, they relax and straighten. This process releases energy in the form of superheated plasma and rapidly flowing jets. On a much larger scale (millions of light years), galactic disks collapse, rapidly shedding angular momentum and in the process generate extended, magnetized jets along their axes. On human scales, laboratory experiments are underway seeking self-organized magnetic structures that would be suitable "bottles’’ for a fusion reactor. We present recent experimental results from the merger of two rings of hot, magnetized plasma in the Swarthmore Spheromak Experiment (SSX). During the merging process, the plasma self-organizes to generate a single, large scale (ρ = 0.2 m, L = 0.6 m), three-dimensional magnetic structure called a field-reversed configuration (FRC). The rate at which the merging proceeds is governed locally by magnetic reconnection in which magnetic fi elds associated with each ring become shared. The magnetic reconnection rate is fast and fully three-dimensional. Magnetic reconnection converts magnetic energy to heat (up to Te 106 K), energetic particles (Ei > 100 eV), and fl ow (up to 100 km/s).

Fri. March 10th, McCook Auditorium, 3:00 pm, Refreshments 2:45 pm

 
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