Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density

Degeling, A. W.; Rae, I. J.; Watt, Clare E. J.; Shi, Quanqi; Rankin, R.; Zong, Qiugang

doi:10.1002/2017ja024874

Cited by 50 publications

(92 citation statements)

References 65 publications

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“…It is evident that the FLRs in Figure cannot be interpreted with the usual 2‐D toroidal FLR theory. The 3‐D nature of the equilibrium requires a theoretical description that is somewhat different to 2‐D (Degeling et al, ; Wright & Elsden, ). Recall that Elsden and Wright () showed that the frequency of Alfvén waves on a given ridge is the same everywhere along the ridge.…”

Section: Simulation Resultsmentioning

confidence: 99%

Simulations of MHD Wave Propagation and Coupling in a 3‐D Magnetosphere

Wright

Elsden

2020

JGR Space Physics

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A 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 L shell, and have a polarization that is midway between toroidal and poloidal.

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Section: Simulation Resultsmentioning

confidence: 99%

Simulations of MHD Wave Propagation and Coupling in a 3‐D Magnetosphere

Wright

Elsden

2020

JGR Space Physics

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“…These equations, along with equation for b 1 μ , form a closed set (along with appropriate boundary conditions) and have been analyzed and modeled by many authors over the last four decades (Allan & Knox, ; Allan & Poulter, ; Degeling & Rankin, ; Degeling et al, , ; Hasegawa & Chen, ; Lee, ; Lee & Lysak, ; Lysak et al, ; Rankin et al, ; Walker, ). The formalism for the wave model presented here is an extension of the approach taken by Rankin and coauthors in a number of previous works (Frycz et al, ; Rankin et al, , ; Wang et al, ).…”

Section: Analytic Model Formulationmentioning

confidence: 99%

Alteration of Particle Drift Resonance Dynamics Near Poloidal Mode Field Line Resonance Structures

et al. 2019

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We examine the effect on drift‐resonant particle dynamics of a strongly peaked internally driven poloidal mode field line resonance (FLR; with specified frequency ω in the Pc5 range and azimuthal mode number m≫1). Using an analytic magneto‐hydrodynamic model in a dipole field to describe the ultra low frequency wave mode, we use the bounce‐averaged formalism of Northrop (1963) to obtain equations of motion for charged particles in the wave frame and find an analytic solution for the case of a temporally constant ultra low frequency wave amplitude profile. Focusing on equatorially mirroring electrons in this study, we demonstrate that, for sufficiently peaked radial profiles, multiple drift resonances appear that are associated with the FLR peak. These are in addition to the well‐known zeroth‐order drift resonance location, occurring when the unperturbed drift speed trueϕ̇0 satisfies the resonance condition ( mtrueϕ̇−ω=0). The additional resonances arise because the strongly peaked FLR wave field components provide sufficiently strong perturbations to the azimuthal drift speed to cause multiple zero crossings in the resonance condition. These additional resonances have trapping periods much lower than that of the zeroth‐order resonance and considerably complicate the electron dynamics. Further properties of these resonances and their measurable effect on electron dynamics are discussed. For example, their effect on observations of energetic electron flux on board satellites in the vicinity of an FLR is calculated and shown to significantly distort the typical signature associated with drift resonance (modulations in electron flux at the wave frequency with a 180° phase change across the resonant energy).

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“…Understanding the structure of the fast mode which develops in an asymmetric equilibrium about noon has been used recently to explain the dawn‐dusk asymmetry of Pc5 wave observations (Wright et al, ). Further, the inclusion of azimuthal magnetic and density asymmetries has also been used to consider the effect of a plasmaspheric plume on ULF wave propagation (Degeling et al, ). A key aspect of the current work is considering the excitation of FLRs in 3‐D (Elsden & Wright, , ; Wright & Elsden, ), where resonances can exist at any given polarization angle between toroidal and poloidal.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Fast Normal Mode Structure and Magnetopause Forcing on FLRs in a 3‐D Waveguide

Elsden

Wright

2019

JGR Space Physics

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This paper investigates the excitation of waveguide modes in a nonuniform dipole equilibrium and, further, their coupling to field line resonances (FLRs). Waveguide modes are fast compressional ultralow frequency (ULF) waves, whose structure depends upon the magnetospheric equilibrium and the solar wind driving conditions. Using magnetohydrodynamic simulations, we consider how the structure of the excited waveguide mode is affected by various forms of magnetopause driving. We find that the waveguide supports a set of normal modes that are determined by the equilibrium. However, the particular normal modes that are excited are determined by the structure of the magnetopause driver. A full understanding of the spatial structure of the normal modes is required in order to predict where coupling to FLRs will occur. We show that symmetric pressure driving about the noon meridian can excite normal modes which remain around to drive resonances for longer than antisymmetric driving. Further, the critical quantity in terms of efficient coupling is the magnetic pressure gradient aligned with the resonance.

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Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density

Cited by 50 publications

References 65 publications

Simulations of MHD Wave Propagation and Coupling in a 3‐D Magnetosphere

Simulations of MHD Wave Propagation and Coupling in a 3‐D Magnetosphere

Alteration of Particle Drift Resonance Dynamics Near Poloidal Mode Field Line Resonance Structures

The Effect of Fast Normal Mode Structure and Magnetopause Forcing on FLRs in a 3‐D Waveguide

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