Quasilinear theories have been shown to well describe a range of transport phenomena in magnetospheric, space, astrophysical and laboratory plasma “weak turbulence” scenarios. It is known that the resonant diffusion quasilinear theory for case uniform background field may formally particle dynamics when electromagnetic wave amplitude growth rates are sufficiently “small”, bandwidth “large”. However, it important note given spectrum would be expected give rise transport, indeed apply...

We derive weak turbulence and quasilinear models for relativistic charged particle dynamics in pitch-angle energy space, due to interactions with electromagnetic waves propagating (anti-)parallel a uniform background magnetic field. use Markovian approach that starts from the consideration of single motion prescribed This has number benefits, including: 1) evident self-consistent relationship between more general theory standard resonant diffusion (as is commonly used e.g. radiation belt...

Sharp boundaries are a key feature of space plasma environments universally, with their wave-like motion (driven by pressure variations or flow shears) playing role in mass, momentum, and energy transfer. This review summarises magnetohydrodynamic surface wave theory particular reference to Earth’s magnetopause, due its mediation the solar-terrestrial interaction. Basic analytic propagating standing waves within simple models presented, highlighting many typically-used assumptions. We raise...

Abstract We present numerical simulations of the excitation resonant poloidal Alfvén waves. The resulting waves could be loosely described as “high‐” ( is azimuthal wave number) in much scale less than direction normal to ‐shells. Such are generally excited by wave‐particle interactions. In this article we show how can a fast mode (of large scale) cold plasma. key property that enables three‐dimensional equilibrium, which facilitates process phasemixing direction. classification high‐ and...

Abstract Ultra‐Low Frequency (ULF) waves are critical drivers of particle acceleration and loss in the Earth's magnetosphere. While statistical models ULF‐induced radial transport have traditionally assumed that uniformly distributed across magnetic local time (MLT), decades observational evidence show significant MLT localization ULF This study presents, for first time, a quasi‐linear diffusion coefficient accounting localized waves. Our results reveal when cover more than 30% MLT,...

Abstract A novel simulation grid is devised that optimized for studying magnetohydrodynamic (MHD) wave coupling and phase mixing in a dipole‐like magnetic field. The model also includes flaring on the dawn dusk flanks. location of magnetopause quite general. In particular, it does not have to coincide with coordinate surface. Simulations indicate central role global fast waveguide modes. These switch from being azimuthally standing nature at noon, propagating antisunward field line...

ABSTRACT We consider the resonant coupling of fast and Alfvén magnetohydrodynamic (MHD) waves in a 3D equilibrium. Numerical solutions to normal modes ( <?CDATA $\propto \exp (-i\omega t)$?> ) are presented, along with theoretical framework interpret them. The we find fundamentally different from those 1D 2D. In there exists an infinite number possible within “Resonant Zone,” show how boundary conditions locally 2D regions can favor particular solutions. A unique feature resonance is...

Abstract The effects of a solar wind pressure pulse on the terrestrial magnetosphere have been observed in detail across multiple datasets. communication these into is known as positive geomagnetic sudden impulse (+SI), and are latitudes different phenomena to characterize propagation +SI through magnetosphere. A superposition Alfvén compressional modes magnetometer signatures, with dominance signatures varying latitude. For first time, collocated lobe reconnection convection vortices region...

Abstract This paper considers the resonant coupling of fast and Alfvén magnetohydrodynamic (MHD) waves. We perform numerical simulations time‐dependent excitation resonances in a dipole magnetic field, with nonuniform density providing 3‐D equilibrium. Wright Elsden (2016) showed that such system where poloidal toroidal eigenfrequencies are different, resonance can have an intermediate polarization, between toroidal. extend this work by driving broadband rather than monochromatic source....

Abstract Resonance Maps depict the possible locations and polarizations of resonant Alfvén waves (Field Line Resonances – FLRs) for a given equilibrium driving frequency. Previously use has been developed gaining insight into behavior in basic potential magnetic fields that allow an orthogonal field aligned coordinate system. In more general these coordinates do not exist. this paper we explore application to such equilibria. A number simulations are presented interpreted using Maps. We find...

Abstract We present results from a 3‐D numerical simulation which investigates the coupling of fast and Alfvén magnetohydrodynamic (MHD) waves in nonuniform dipole equilibrium. This represents time‐dependent extension normal mode ( ) analysis Wright Elsden (2016) provides theoretical basis for understanding resonances. show that these are fundamentally different to resonances 1‐D 2‐D. demonstrate temporal behavior resonance, is formed within “Resonant Zone”; channel domain where family...

Abstract Ultra low frequency (ULF) waves play a crucial role in transporting and coupling energy within the magnetosphere. During geomagnetic storms, dayside magnetospheric ULF wave power is highly variable with strong enhancements that are dominated by elevated solar wind driving. However, radial distribution of complex ‐ controlled interdependently external driving internal structuring. We conducted statistical analysis observed storm‐time from Van Allen Probes spacecraft 2012–2016....

Abstract Recent work has shown that field line resonances (FLRs) can form with intermediate magnetic polarizations, is, between toroidal (azimuthal) and poloidal (radial). In this case, they are referred to as “3‐D”, given the equilibrium therefore associated wave solutions vary in all three dimensions. Such 3‐D variations medium be expected magnetosphere particular during presence of a plasmaspheric drainage plume dusk flank. strong field‐aligned currents driven by FLRs along contours...

Abstract We investigate how initially high‐ m , poloidal Alfvén waves evolve using a numerical model solving the ideal, cold, linear magnetohydrodynamic (MHD) equations in 2‐D dipole coordinate system. The curved magnetic geometry provides key difference between and toroidal frequencies of any one field line. A polarization rotation from toward predicted Cartesian box theory still occurs but now with following contours frequency, which moves wave across lines. structure these depends on...

Abstract Field line resonances (FLRs) are observed to occur preferentially and have larger amplitudes at dawn compared dusk. We present simulations of FLR excitation in a magnetospheric waveguide that can reproduce this behavior. Crucially, our equilibrium is asymmetric about noon. Even when system driven symmetric fashion noon, the fast waves established magnetosphere develop asymmetries—as do FLRs they excite. Fast mode ray trajectories employed show asymmetry evolves due refraction....

Abstract This paper investigates the excitation of waveguide modes in a nonuniform dipole equilibrium and, further, their coupling to field line resonances (FLRs). Waveguide are fast compressional ultralow frequency (ULF) waves, whose structure depends upon magnetospheric and solar wind driving conditions. Using magnetohydrodynamic simulations, we consider how excited mode is affected by various forms magnetopause driving. We find that supports set normal determined equilibrium. However,...

Abstract Field Line Resonances (FLRs) are a critical component in Earth's magnetospheric dynamics, associated with the transfer of energy between Ultra Low Frequency waves and local plasma populations. In this study we investigate how polarisation FLRs impacted by cold density distributions during geomagnetic storms. We present an analysis Van Allen Probe A observations, where spacecraft traversed storm time plasmaspheric plume. show that FLR is significantly altered at sharp azimuthal...

Abstract We numerically model ultralow frequency (ULF) waves in the magnetosphere assuming an ideal, low‐ β , inhomogeneous plasma waveguide. The waveguide is based on hydromagnetic box model. develop a novel boundary condition that drives magnetospheric by pressure perturbations, order to simulate solar wind dynamic fluctuations disturbing magnetopause. applied observations from Cluster and Time History of Events Macroscale Interactions during Substorms. Our able reproduce similar wave...

The resonant excitation of Alfvén waves using the fast magnetosonic mode is important in space plasmas. In this paper, we consider a simple model three-dimensional (3D) coronal arcade. A numerical approach used to produce driven normal mode. We find that coupling can occur 3D, but there are new features absent 2D. particular, polarisation vary with position throughout Resonant Zone. Moreover, an infinite number possible paths exist on.

Abstract Many previous studies have reported that magnetospheric ultralow frequency waves excited by interplanetary shocks exhibit a strong toroidal component, corresponding to azimuthal displacement of magnetic field lines. However, the oscillations an shock on 27 February 2014 and observed dayside multiple spacecraft were accompanied poloidal component (radial line displacement). The changed with radial distance as expected for standing Alfvén waves. We run 3D linear numerical simulation...

Abstract We present an analytical method for determining incident and reflection coefficients flank ULF compressional waveguide modes in Earth's magnetosphere. In the magnetosphere, waves propagate azimuthally but exhibit a mixed standing/propagating nature radially. Understanding this radial dependence will yield information on energy absorption transport of these waves. provide step by that can be applied to observations waves, which separates fluctuations into reflected parts. As means...

Abstract Previous observational studies have shown that the natural Alfvén frequencies of geomagnetic field lines vary significantly over course a storm, decreasing by up to 50% from their quiet time values outside plasmasphere. This was recently demonstrated statistically using ground magnetometer observations across 132 storm events (Wharton et al., 2020). then brings into question where line resonances (FLRs) will form in storm‐time conditions relative times. With radiation belt dynamics...