"Firehose and Mirror Instabilities in a Collisionless Shearing Plasma," by Matthew Kunz (Princeton University)

Tuesday, May 6, 2014 - 11:30am to 12:30pm
Plasma Seminars

Plasma Seminar

Tuesday, May 6
11:30 AM
Physics & Astronomy Building (PAB) Room 4-330

Guest Speaker: Matthew Kunz (Princeton University)

Talk Title: "Firehose and Mirror Instabilities in a Collisionless Shearing Plasma"


Describing the large-scale behavior of weakly collisional magnetized plasmas, such as the solar wind, black-hole accretion flows, or the intracluster medium of galaxy clusters, necessitates a detailed understanding of the kinetic-scale physics governing the dynamics of magnetic fields and the transport of momentum and heat. This physics is complicated by the fact that such plasmas are expected to exhibit particle distribution functions with unequal thermal pressures in the directions parallel and perpendicular to the local magnetic field. This pressure anisotropy can trigger fast microscale instabilities -- namely, firehose and mirror -- which solar-wind observations suggest to be effective at regulating the pressure anisotropy to marginally stable levels. In this talk, I will use the results of weakly nonlinear theory and of new hybrid-kinetic particle-in-cell simulations to address how marginal stability is achieved and maintained in a plasma whose pressure anisotropy is continuously driven by a shearing magnetic field. These results, coupled with ongoing studies of collisionless magnetorotational and kinetic-Alfven-wave turbulence, will be placed within the larger context of formulating a pragmatic framework for modeling multiscale dynamics in space and astrophysical plasmas.