Coupling Between Alfvén Wave and Kelvin–Helmholtz Waves in the Low Latitude Boundary Layer

Kim, Eun Hwa; Nykyri, K.

doi:10.3389/fspas.2021.785413

Cited by 5 publications

(3 citation statements)

References 49 publications

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“…In the present study, the length scales of the flow and Alfvén velocity gradients are equal, which limits the development of RFI. For further discussions on RFI, the reader is referred to the recent article by Kim et al [73] and references therein.…”

Section: Discussionmentioning

confidence: 99%

The inviscid incompressible limit of Kelvin–Helmholtz instability for plasmas

Briard,

Ripoll,

Michael

et al. 2024

Front. Phys.

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Introduction: The Kelvin–Helmholtz Instability (KHI) is an interface instability that develops between two fluids or plasmas flowing with a common shear layer. KHI occurs in astrophysical jets, solar atmosphere, solar flows, cometary tails, planetary magnetospheres. Two applications of interest, encompassing both space and fusion applications, drive this study: KHI formation at the outer flanks of the Earth’s magnetosphere and KHI growth from non-uniform laser heating in magnetized direct-drive implosion experiments. Here, we study 2D KHI with or without a magnetic field parallel to the flow. We use both the GAMERA code, which solves the compressible Euler equations, and the STRATOSPEC code, which solves the Navier-Stokes equations under the Boussinesq approximation, coupled with the magnetic field dynamics. GAMERA is a global three-dimensional MHD code with high-order reconstruction in arbitrary nonorthogonal curvilinear coordinates, which is developed for a large range of astrophysical applications. STRATOSPEC is a three-dimensional pseudo-spectral code with an accuracy of infinite order (no numerical diffusion). Magnetized KHI is a canonical case for benchmarking hydrocode simulations with extended MHD options.Methods: An objective is to assess whether or not, and under which conditions, the incompressibility hypothesis allows to describe a dynamic compressible system. For comparing both codes, we reach the inviscid incompressible regime, by decreasing the Mach number in GAMERA, and viscosity and diffusion in STRATOSPEC. Here, we specifically investigate both single-mode and multi-mode initial perturbations, either with or without magnetic field parallel to the flow. The method relies on comparisons of the density fields, 1D profiles of physical quantities averaged along the flow direction, and scale-by-scale spectral densities. We also address the triggering, formation and damping of filamentary structures under varying Mach number or Atwood number, with or without a parallel magnetic field.Results: Comparisons show very satisfactory results between the two codes. The vortices dynamics is well reproduced, along with the breaking or damping of small-scale structures. We end with the extraction of growth rates of magnetized KHI from the compressible regime to the incompressible limit in the linear regime assessing the effects of compressibility under increasing magnetic field.Discussion: The observed differences between the two codes are explained either from diffusion or non-Boussinesq effects.

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Section: Discussionmentioning

confidence: 99%

The inviscid incompressible limit of Kelvin–Helmholtz instability for plasmas

Briard,

Ripoll,

Michael

et al. 2024

Front. Phys.

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“…Characterization of dayside properties is again more difficult for electrons, in that they typically occur at higher‐latitudes than proton IBs, mapping them closer to the magnetopause. These regions are host to several processes such as magnetic reconnection (Trattner et al., 2021) and the Kelvin‐Helmholtz instability (Kim et al., 2022), which can give rise to similar dispersive isotropic particle scattering onto Earth‐connected field lines. Observations of protons falling into these categories have long been made; the latter of which are often grouped into the umbrella of “magnetopause scattering” (e.g., Lyons et al., 1987).…”

Section: Introductionmentioning

confidence: 99%

Statistical Characteristics of the Electron Isotropy Boundary

Wilkins,

Angelopoulos,

Runov

et al. 2023

JGR Space Physics

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Utilizing observations from the ELFIN satellites, we present a statistical study of ∼2000 events in 2019‐2020 characterizing the occurrence in magnetic local time (MLT) and latitude of ≥50 keV electron isotropy boundaries (IBs) and associated electron precipitation. The isotropy boundary of an electron of a given energy is the magnetic latitude poleward of which persistent isotropized pitch‐angle distributions (Jprec/Jperp ∼ 1) are first observed to occur, interpreted as resulting from magnetic field‐line curvature scattering (FLCS) in the equatorial magnetosphere. We find that energetic electron IBs can be well‐recognized on the nightside from dusk until dawn, under all geomagnetic activity conditions, with a peak occurrence rate of almost 90% near ∼22 hours in MLT, remaining above 80% from 21 to 01 MLT. The observed IBs span IGRF magnetic latitudes of 60°‐74° with a maximum occurrence between 66°‐71° (L of 6‐8), trending toward lower latitudes and pre‐midnight local times with activity. The precipitating energy flux of ≥50 keV electrons averaged over the IB‐associated latitudes varies over four orders of magnitude, up to 1 erg/cm2‐s, and often includes wide‐energy electron spectra exceeding 1 MeV. The IB‐associated energies and precipitating fluxes also exhibit peak values near midnight for low activity, shifting toward pre‐midnight for elevated activity. The average total precipitating power deposited over the high‐latitude nightside atmosphere (55° to 80°; IGRF L ≥3) attributed to IBs is 10‐20%, or 10 MW, but at times can approach 100% of the total ≥50 keV electron energy deposition over the entire sub‐auroral and auroral zone region, exceeding 1 GW.

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“…Chen et al., 2015; Izutsu et al., 2012; Yao et al., 2011). Indeed, the magnetosheath is filled by a wide range of ion‐kinetic scale waves (Anderson & Fuselier, 1993; Rakhmanova et al., 2021; Sahraoui et al., 2003; Song et al., 1994; Zimbardo et al., 2010) generated either by local instabilities of anisotropic ion populations (Anderson et al., 1994; Gary & Lee, 1994; Schwartz et al., 1996) or by mode conversion from large‐scale magnetohydrodynamic (MHD) waves to ion‐kinetic scale waves (C. C. Chaston et al., 2007; Cheng et al., 2020; Johnson et al., 2001; Kim et al., 2022; Lin et al., 2012; Shi et al., 2013).…”

Section: Introductionmentioning

confidence: 99%

On the Role of Kinetic Alfven Waves in the Magnetosheath Ion Thermalization Around the Night‐Side Magnetopause

et al. 2023

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The solar wind ion transport across the magnetopause is one of the main sources of plasma for the Earth's magnetotail. Such a transport is supported by various dynamic processes at the flank magnetopause, where wave‐particle interactions play a crucial role in ion flow thermalization and diffusion across magnetic field surfaces of the magnetopause tangential discontinuity. In this paper we numerically model such ion thermalization by the most intense electromagnetic waves observed in the magnetosheath, kinetic Alfven waves. We aim to develop an approach for long‐term simulations of ion scattering by waves and ion dynamics around realistic magnetopause magnetic fields. This approach is based on a combination of test particle simulations and stochastic differential equations modeling ion diffusion in velocity space. We demonstrate that for realistic magnetopause configuration and wave characteristics, the magnetosheath ion flow can be substantially thermalized around the magnetopause. This result explains observations of ion energy conservation across the flank magnetopause: kinetic and thermal energies of flowing magnetosheath ions approximately equal to the thermal energy of stagnant magnetospheric ions.

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Coupling Between Alfvén Wave and Kelvin–Helmholtz Waves in the Low Latitude Boundary Layer

Cited by 5 publications

References 49 publications

The inviscid incompressible limit of Kelvin–Helmholtz instability for plasmas

The inviscid incompressible limit of Kelvin–Helmholtz instability for plasmas

Statistical Characteristics of the Electron Isotropy Boundary

On the Role of Kinetic Alfven Waves in the Magnetosheath Ion Thermalization Around the Night‐Side Magnetopause

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