TAPIR Seminar
Paul Bellan, Professor of Applied Physics at Caltech, has worked on many aspects of experimental and theoretical plasma physics. Recent experimental work includes lab scale versions of astrophysical jets, of solar coronal loops, and dusty plasmas where the dust is water ice. Theoretical work has included various types of plasma waves, MHD jets, and particle orbits in the presence of complex fields.
Ions and neutrals in the weakly ionized plasma of an accretion disk are tightly bound because of the high ion-neutral collision frequency. A cluster of a statistically large number of ions and neutrals behaves as a fluid element having the charge of the ions and the mass of the neutrals. This fluid element is effectively a metaparticle having such an extremely small charge to mass ratio that its cyclotron frequency can be of the order of the Kepler angular frequency. In this case, metaparticles with a critical charge to mass ratio can have zero canonical angular momentum. Zero canonical angular momentum metaparticles experience no centrifugal force and spiral inward towards the central body. Accumulation of these inward spiraling metaparticles near the central body produces radially and axially outward electric fields. The axial outward electric field drives an out-of-plane poloidal electric current along arched poloidal flux surfaces in the highly ionized volume outside the disk. This out-of-plane current and its associated magnetic field produce forces that drive bidirectional astrophysical jets flowing normal to and away from the disk. The poloidal electric current circuit removes angular momentum from the accreting mass and deposits this removed angular momentum at near infinite radius in the disk plane. The disk region is an electric power source (E⋅J<0) while the jet region is an electric power sink (E⋅J>0).