University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Tuesday, November 5th 2019
1:25 pm:
Space Physics Seminar in Tate 201-20
Speaker: Aaron West
Subject: "Numerical Studies of Kinetic Field Line Resonances"

Field Line Resonances (FLRs) form as eigenmodes of Alfvén waves between conductive ionospheric boundaries along geomagnetic field lines. When kinetic Alfvén waves develop along FLRs, electron inertial effects can limit the width of the structure, leading to dispersive wave trains, stronger parallel electric fields, and particle acceleration. Kinetic field line resonances (KFLRs) have been detected by the Van Allen Probes in conjunction with steep density gradients, but their evolution and dynamics have been insufficiently modeled.
A numerical 3D time-domain model explores the structure of FLRs in an idealized two-fluid dipole scheme. A finite conductivity current sheet ionospheric boundary condition allows for Hall coupling between the shear Alfvén and fast mode waves. This coupling can mode convert fast waves driven by dipolarization flows into Alfvén waves, feeding FLR wave amplitudes. Gradients in Alfven speed can induce phase mixing between shear Alfven and slow mode waves, reducing the coherent perpendicular FLR wavelengths. Once wavelengths become comparable to electron inertial length scales, FLRs begin to exhibit kinetic effects, and require Debye scale resolution. The model provides the framework for future investigations of kinetic plasma wave evolution dynamics.

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