American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 1561155 bytes)

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. A9, 1225, doi:10.1029/2001JA000135, 2002

Ultralow-frequency magnetohydrodynamics in boundary-constrained geomagnetic flux coordinates

Jeffrey A. Proehl

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA


William Lotko

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA


Igor Kouznetsov

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA


Shireen D. Geimer

Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA


Abstract

A new method is described for constructing geomagnetic flux coordinates, constrained by magnetospheric and ionospheric boundary surfaces. The technique is especially useful for computing boundary value solutions in a geometry defined by a realistic, three-dimensional geomagnetic field with boundary conditions specified on surfaces oriented arbitrarily relative to the background magnetic field. An adaptable algorithm for calculating the metric tensor for a general class of geomagnetic flux coordinate systems is presented. Application to ultralow-frequency wave propagation in the magnetosphere is illustrated by solving the equations of linear, one-fluid magnetohydrodynamics for the driven field line resonance in a dipolar geomagnetic field bounded by a spherical ionosphere. A novel diagnostic for energy flow in the driven resonance problem shows that MHD wave power flows “radially” inward as a compressional wave from the boundary driver to the resonant flux surface, is diverted azimuthally at the resonant surface, and becomes field-aligned in the resonant surface by coupling to the magnetically guided Alfvén wave at locations where the shear mode is in azimuthal phase quadrature with the compressional driver.

Published 5 September 2002.

Index Terms: 2752 Magnetospheric Physics: MHD waves and instabilities; 2753 Magnetospheric Physics: Numerical modeling; 7843 Space Plasma Physics: Numerical simulation studies; 7859 Space Plasma Physics: Transport processes.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 1561155 bytes)

Citation: Proehl, J. A., W. Lotko, I. Kouznetsov, and S. D. Geimer (2002), Ultralow-frequency magnetohydrodynamics in boundary-constrained geomagnetic flux coordinates, J. Geophys. Res., 107(A9), 1225, doi:10.1029/2001JA000135.