Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B


Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

Blake Stauffer
Physics Dept./GI UAF



Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability.   In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016).  We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter’s inner and middle magnetosphere.  A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions.  Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity).  We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998).  Prescribed perpendicular wave modes are seeded with an initial velocity perturbation.  We then extend the model to three dimensions, introducing a stabilizing parallel wave vector.  Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc’s resonant cavity.  We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength.  Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.


Friday, 15 September 2017

Globe Room, Elvey Building

3:45 PM