Field line resonances — that is, Alfvén waves bouncing between the northern and southern foot points of a geomagnetic ﬁeld line — serve to energize magnetospheric particles through drift-resonant interactions, carry energy from high to low altitude, induce currents in the magnetosphere, and accelerate particles into the atmosphere. Wave structure and polarization signiﬁcantly impact the execution these roles. The present work showcases a new two and a half dimensional code, Tuna, ideally suited to model FLRs, with the ability to consider large-but-ﬁnite azimuthal modenumbers, coupling between the poloidal, toroidal, and compressional modes, and arbitrary harmonic structure. Using Tuna, the interplay between Joule dissipation and poloidal-to-toroidal rotation is considered for both dayside and nightside conditions. An attempt is also made to demystify giant pulsations, a class of FLR knows for its distinctive ground signatures. Numerical results are supplemented by a survey of ∼700 FLRs using data from the Van Allen Probes, the ﬁrst such survey to characterize each event by both polarization and harmonic. The combination of numerical and observational results suggests an explanation for the disparate distributions observed in poloidal and toroidal FLR events.
University of Minnesota Ph.D. dissertation. April 2016. Major: Physics. Advisor: Robert Lysak. 1 computer file (PDF); vii, 124 pages.
Modeling Pc4 Pulsations in Two and a Half Dimensions with Comparisons to Van Allen Probes Observations.
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