Observations of turbulence in a Kelvin‐Helmholtz event on 8 September 2015 by the Magnetospheric Multiscale mission

Stawarz, J. E.; Eriksson, S.; Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Pouquet, A.; Burch, J. L.; Giles, B. L.; Khotyaintsev, Yuri V.; Contel, O. Le; Lindqvist, Per‐Arne; Magnes, W.; Pollock, C. J.; Russell, C. T.; Strangeway, R. J.; Torbert, R. B.; Avanov, L. A.; Dorelli, J.; Eastwood, J. P.; Gershman, D. J.; Goodrich, K.; Malaspina, D.; Marklund, Göran; Mirioni, Laurent; Sturner, A. P.

doi:10.1002/2016ja023458

Cited by 97 publications

(109 citation statements)

References 90 publications

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“…The E spectral index dramatically steepens at frequencies above ~3 f lh (~20 Hz). These observations are consistent with previously reported turbulence spectra in the magnetosphere with the exception that B has a shallower spectral index between f ci and f lh (Ergun et al, ; Stawarz et al, ).…”

Section: Observationssupporting

confidence: 93%

“…Plasma turbulence is active in many astrophysical settings (e.g., the interstellar medium Falceta‐Gonçalves et al, ). It is central to the solar corona (e.g., Cranmer et al, ), the solar wind (e.g., Matthaeus et al, ), and active regions of the Earth's magnetosphere (Borovsky et al, ; Borovsky & Funsten, ; Chasapis et al, ; Stawarz et al, ; Stawarz, Ergun, & Goodrich, ; Vörös et al, ; Weygand et al, ; Zimbardo et al, ). In particular, plasma sheet turbulence is well established (ibid).…”

Section: Introductionmentioning

confidence: 99%

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Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail

Ergun

Goodrich

Wilder

et al. 2018

Geophysical Research Letters

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We report observations of turbulent dissipation and particle acceleration from large‐amplitude electric fields (E) associated with strong magnetic field (B) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti‐earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally >100 keV, and strong variation. There are numerous occurrences of |E| >100 mV/m including occurrences of large potentials (>1 kV) parallel to B and occurrences with extraordinarily large J · E (J is current density). In this event, we find that the perpendicular contribution of J · E with frequencies near or below the ion cyclotron frequency (fci) provide the majority net positive J · E. Large‐amplitude parallel E events with frequencies above fci to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration.

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Section: Observationssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail

Ergun

Goodrich

Wilder

et al. 2018

Geophysical Research Letters

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“…The latter decouples from the magnetic field and typically shows a steeper and much more variable power law (e.g., Šafránková et al 2016). On the contrary, the electric field spectrum flattens (Bale et al 2005;Sahraoui et al 2009;Salem et al 2012), dominating over the magnetic field's, with a typical spectral index of about −0.8 (e.g., Stawarz et al 2016;Matteini et al 2017), as predicted from the generalized Ohm's law (Franci et al 2015a). Moreover, an increase in the magnetic compressibility Kiyani et al 2013) and a reduced variance anisotropy (Podesta & TenBarge 2012) are also observed.…”

Section: Introductionmentioning

confidence: 94%

Solar Wind Turbulent Cascade from MHD to Sub-ion Scales: Large-size 3D Hybrid Particle-in-cell Simulations

Franci

Landi

Verdini

et al. 2018

ApJ

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Properties of the turbulent cascade from fluid to kinetic scales in collisionless plasmas are investigated by means of large-size 3D hybrid (fluid electrons, kinetic protons) particle-in-cell simulations. Initially isotropic Alfvénic fluctuations rapidly develop a strongly anisotropic turbulent cascade, mainly in the direction perpendicular to the ambient magnetic field. The omnidirectional magnetic field spectrum shows a double power-law behavior over almost two decades in wavenumber, with a Kolmogorov-like index at large scales, a spectral break around ion scales, and a steepening at sub-ion scales. Power laws are also observed in the spectra of the ion bulk velocity, density, and electric field, at both magnetohydrodynamic (MHD) and kinetic scales. Despite the complex structure, the omnidirectional spectra of all fields at ion and sub-ion scales are in remarkable quantitative agreement with those of a 2D simulation with similar physical parameters. This provides a partial, a posteriori validation of the 2D approximation at kinetic scales. Conversely, at MHD scales, the spectra of the density and of the velocity (and, consequently, of the electric field) exhibit differences between the 2D and 3D cases. Although they can be partly ascribed to the lower spatial resolution, the main reason is likely the larger importance of compressible effects in the full 3D geometry. Our findings are also in remarkable quantitative agreement with solar wind observations.

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“…The Kelvin‐Helmholtz (KH) instability driven by a large sheared flow (Chandrasekhar, ) is often considered as one of the major mechanisms of the “viscous‐like” interaction (Axford, ) between the solar wind and the Earth's magnetosphere during northward interplanetary magnetic field (IMF) conditions (Johnson et al, ). Nonlinear KH waves are ubiquitously observed by different spacecrafts (Chen & Kivelson, ; Eriksson et al, ; Fairfield et al, ; Hasegawa et al, , ; Li et al, ; Nakamura et al, ; Nykyri et al, ; Stawarz et al, ; Vernisse et al, ) at low latitudes under both northward and southward IMF conditions (Hwang et al, ; Kavosi & Raeder, ; Walsh et al, ; Yan et al, ), as well as at high latitudes for dawnward and duskward IMF conditions (Hwang et al, ; Ma, Otto, Delamere, et al, ), which are consistent with global magnetohydrodynamics (MHD) simulations (Guo et al, ; Hwang et al, ; Li et al, ; Merkin et al, ). Therefore, it is of importance to identify and quantify how efficiently the nonlinear KH instability transports magnetic flux, mass, flux tube entropy, and momentum.…”

Section: Introductionmentioning

confidence: 99%

Plasma Transport Driven by the Three‐Dimensional Kelvin‐Helmholtz Instability

et al. 2017

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It has been well demonstrated that the nonlinear Kelvin‐Helmholtz (KH) instability plays a critical role for the solar wind interaction with the Earth's magnetosphere. Although the two‐dimensional KH instability has been fully explored during the past decades, more and more studies show the fundamental difference between the two‐ and three‐dimensional KH instability. For northward interplanetary magnetic field (IMF) conditions, the nonlinear KH wave that is localized in the vicinity of the equatorial plane can dramatically bend the magnetic field line, generating strong antiparallel magnetic field components at high latitudes in both North and South Hemispheres, which satisfy the onset condition for magnetic reconnection. This high‐latitude double reconnection process can exchange the portion of magnetosheath and magnetospheric flux tubes between those two reconnection sites. This study used a high‐resolution 3‐D magnetohydrodynamic simulation to demonstrate that nonlinear KH waves can generate a large amount of double‐reconnected flux during the northward IMF condition, which can efficiently transport the plasma with a high diffusion coefficient of 1 × 1010 m2 s−1 for typical magnetopause conditions at the Earth. The presence of the magnetic field component along the shear flow direction not only decreases the KH growth rate but also causes north‐south asymmetry, which generates more open flux and reduces the efficiency of the plasma transport process.

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Observations of turbulence in a Kelvin‐Helmholtz event on 8 September 2015 by the Magnetospheric Multiscale mission

Cited by 97 publications

References 90 publications

Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail

Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail

Solar Wind Turbulent Cascade from MHD to Sub-ion Scales: Large-size 3D Hybrid Particle-in-cell Simulations

Plasma Transport Driven by the Three‐Dimensional Kelvin‐Helmholtz Instability

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