Electron-scale Magnetic Peaks Upstream of Mercury’s Bow Shock: MESSENGER Observations

Chen, Yuanqiang; Wang, G. Q.; Wu, Mingyu; Xiao, Shulong; Zhang, T. L.

doi:10.3847/1538-4357/ac80c0

Cited by 2 publications

(2 citation statements)

References 55 publications

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“…The earliest observations of MHs date back to the work of Turner et al (1977), where these structures were identified for the first time in the solar wind (SW). Since then, satellite measurements have revealed that MHs are abundant not only in the SW (Winterhalter et al 1995(Winterhalter et al , 2000Chisham et al 2000;Russell et al 2008;Zhang et al 2008;Wang et al 2020a;Xiao et al 2014;Wang et al 2021b,c), but also in the Earth's magnetotail (Ge et al 2011;Sun et al 2012;Balikhin et al 2012;Huang et al 2019;Shustov et al 2019;Liu et al 2021), planetary magnetosheaths (Johnson & Cheng 1997;Soucek et al 2008;Volwerk et al 2008;Yao et al 2017;Huang et al 2017a;Zhong et al 2019;Yao et al 2020;Karlsson et al 2021;Huang et al 2021;Goodrich et al 2021), planetary bow shocks (Cattaneo et al 1998;Wang et al 2021a;Chen et al 2022;Huang et al 2022) and around comets (Russell et al 1987;Volwerk et al 2008). Magnetic holes come in many different sizes, covering a very broad range of scales.…”

Section: Introductionmentioning

confidence: 99%

Generation of sub-ion scale magnetic holes from electron shear flow instabilities in plasma turbulence

Arrò

Pucci

Califano

et al. 2023

Preprint

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<p>Magnetic holes are coherent structures associated with a strong depression in the magnetic field amplitude. Such structures are ubiquitous in space plasmas and are observed in the solar wind, in planetary bow shocks and magnetosheaths, in the Earth's magnetotail and around comets. Magnetic holes may have very different sizes and properties. The largest ones have a size of hundreds of ion gyroradii while the smallest ones are sub-ion scale structures of the order of a few electron gyroradii. The drop in magnetic field amplitude associated with magnetic holes is often sustained by an increase in plasma density and enhanced ion and electron temperature anisotropies, with temperatures that are typically higher in the plane perpendicular to the local magnetic field. These properties seem to suggest that the generation of magnetic holes may result from the nonlinear evolution of mirror modes whose growth is fed by perpendicular temperature anisotropies and that are characterized by anticorrelated magnetic field and density perturbations. Some observational and numerical studies seem to support the idea of a scenario in which magnetic holes are generated by the mirror instability but in many cases this picture is not consistent with observations, especially in the case of sub-ion scale magnetic holes for which a number of possible generation mechanisms have been considered. Hence, the origin of magnetic holes is still controversial and under debate.&#160;</p> <p>Plasma turbulence is also known as a driver for the generation of coherent structures and may play a key role in the formation of magnetic holes, especially in the solar wind and in the Earth's magnetosheath that are in a turbulent state. Indeed, numerical simulations of plasma turbulence show that sub-ion scale magnetic holes can develop self-consistently out of small scale magnetic fluctuations that locally reduce the magnetic field amplitude and trap hot electrons. However, it is still unclear how such small scale fluctuations can emerge in a turbulent plasma where energy is typically injected at large scales. In this work, we study the formation of sub-ion scale magnetic holes by means of fully kinetic particle-in-cell simulations of plasma turbulence. We show that by injecting energy at scales relatively large with respect to ion scales, the turbulence naturally tends to generate sub-ion scale electron velocity shear layers associated with elongated magnetic field grooves. These elongated magnetic dips then become unstable and break up into sub-ion scale magnetic holes characterized by an intense azimuthal electron current and a strong perpendicular electron temperature anisotropy. We show that the properties of magnetic holes generated by this mechanism are consistent with satellite observations. Our results may provide a possible explanation of how magnetic holes develop in a realistic turbulent environment.</p>

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Section: Introductionmentioning

confidence: 99%

Generation of sub-ion scale magnetic holes from electron shear flow instabilities in plasma turbulence

Arrò

Pucci

Califano

et al. 2023

Preprint

View full text Add to dashboard Cite

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“…The earliest observations of MHs date back to the work of Turner et al (1977), where these structures were identified for the first time in the solar wind (SW). Since then, satellite measurements have revealed that MHs are abundant not only in the SW (Winterhalter et al 1995;Chisham et al 2000;Winterhalter et al 2000;Russell et al 2008;Zhang et al 2008;Xiao et al 2014;Wang et al 2020aWang et al , 2021bWang et al , 2021c but also in the Earth's magnetotail (Ge et al 2011;Balikhin et al 2012;Sun et al 2012;Huang et al 2019;Shustov et al 2019;Liu et al 2021;Wang et al 2022), in planetary magnetosheaths (Johnson & Cheng 1997;Soucek et al 2008;Volwerk et al 2008;Huang et al 2017a;Yao et al 2017;Zhong et al 2019;Yao et al 2020;Goodrich et al 2021;Huang et al 2021;Karlsson et al 2021;Wu et al 2021;Chen et al 2022b), in planetary bow shocks (Cattaneo et al 1998;Wang et al 2021a;Chen et al 2022a;Huang et al 2022), and around comets (Russell et al 1987;Volwerk et al 2008). MHs come in many different sizes, covering a very broad range of scales.…”

Section: Introductionmentioning

confidence: 99%

Generation of Subion Scale Magnetic Holes from Electron Shear Flow Instabilities in Plasma Turbulence

Arrò,

Pucci,

Califano

et al. 2023

ApJ

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Magnetic holes (MHs) are coherent structures associated with strong magnetic field depressions in magnetized plasmas. They are observed in many astrophysical environments at a wide range of scales, but their origin is still under debate. In this work, we investigate the formation of subion scale MHs using a fully kinetic 2D simulation of plasma turbulence initialized with parameters typical of the Earth’s magnetosheath. Our analysis shows that the turbulence is capable of generating subion scale MHs from large scale fluctuations via the following mechanism: first, the nonlinear large scale dynamics spontaneously leads to the development of thin and elongated electron velocity shears; these structures then become unstable to the electron Kelvin–Helmholtz instability and break up into small scale electron vortices; the electric current carried by these vortices locally reduces the magnetic field, inducing the formation of subion scale MHs. The MHs thus produced exhibit features consistent with satellite observations and with previous numerical studies. We finally discuss the kinetic properties of the observed subion scale MHs, showing that they are characterized by complex non-Maxwellian electron velocity distributions exhibiting anisotropic and agyrotropic features.

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Electron-scale Magnetic Peaks Upstream of Mercury’s Bow Shock: MESSENGER Observations

Cited by 2 publications

References 55 publications

Generation of sub-ion scale magnetic holes from electron shear flow instabilities in plasma turbulence

Generation of sub-ion scale magnetic holes from electron shear flow instabilities in plasma turbulence

Generation of Subion Scale Magnetic Holes from Electron Shear Flow Instabilities in Plasma Turbulence

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