Abstract
AbstractA novel simulation grid is devised that is optimized for studying magnetohydrodynamic (MHD) wave coupling and phase mixing in a dipole‐like magnetic field. The model also includes flaring on the dawn and dusk flanks. The location of the magnetopause is quite general. In particular, it does not have to coincide with a coordinate surface. Simulations indicate the central role of global fast waveguide modes. These switch from being azimuthally standing in nature at noon, to propagating antisunward on the flanks. The field line resonances (FLRs) seen in the simulation results are three dimensional and not strictly azimuthally polarized. When a plume is present, the FLRs cross a range of 2 in shell, and have a polarization that is midway between toroidal and poloidal.
Highlights
Simulating coupled magnetohydrodynamic (MHD) waves in a realistic magnetic geometry is fraught with difficulties, and every simulation code to date has various advantages and disadvantages
The drawback with these codes is normally the use of a Cartesian simulation grid, which is not optimal for studying phase-mixed Alfvén waves: consider an field line resonances (FLRs) that has a width of 1 RE in the equatorial plane at L = 8, which is resolved by a uniform Cartesian grid of resolution 0.1 RE
The amplitude of the FFT peaks does depend upon the driver: it is necessary for the FFT of the driver to have significant power at the waveguide mode frequencies if they are to be excited significantly
Summary
Simulating coupled magnetohydrodynamic (MHD) waves in a realistic magnetic geometry is fraught with difficulties, and every simulation code to date has various advantages and disadvantages. Global simulations have the advantage of driving the magnetosphere with a self-consistent magnetosheath The drawback with these codes is normally the use of a Cartesian simulation grid, which is not optimal for studying phase-mixed Alfvén waves: consider an FLR that has a width of 1 RE in the equatorial plane at L = 8, which is resolved by a uniform Cartesian grid of resolution 0.1 RE. In this paper we adopt an equatorial profile for the magnetopause based upon the model given by Shue et al (1997) Whilst this can capture the flaring nature of the magnetospheric flanks realistically, it comes at the cost of not coinciding with an orthogonal coordinate surface. The paper is structured as follows: Section 2 describes the simulation grid; section 3 describes the simulation details and boundary conditions; section 4 presents simulation results, and section 5 gives some concluding remarks
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