Browsing by Subject "Alfven Waves"

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    Modeling Pc4 Pulsations in Two and a Half Dimensions with Comparisons to Van Allen Probes Observations
    (2016-04) McEachern, Charles
    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.
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    Numerical Model for the propagation of Alfven Waves produced by Jupiter's moon Io
    (2022-11-28) Lysak, Robert L; lysak001@umn.edu; Lysak, Robert L; Minnesota Institute for Astrophysics Space Physics Group
    We present first results from a new numerical model to describe the propagation of these Alfvén waves in the Io-Jupiter system. The model is cast in magnetic dipole coordinates and includes a dense plasma torus that is centered around the centrifugal equator. Results are presented for two density models, showing the dependence of the interaction on the magnetospheric density. The effect of the conductance of Jupiter’s ionosphere is considered. A model for the development of parallel electric fields is introduced, indicating that the main auroral footprints of Io can generated parallel potentials of up to 100 kV.