Proton Temperature Anisotropy and Magnetic Reconnection in the Solar Wind: Effects of Kinetic Instabilities on Current Sheet Stability

Matteini, Lorenzo; Landi, Simone; Velli, Marco; Matthaeus, W. H.

doi:10.1088/0004-637x/763/2/142

Cited by 25 publications

(28 citation statements)

References 40 publications

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“…Besides of that, all the phenomena related with bifurcation happens close to the center of the CS, especially the reduction in the temperature anisotropy, where this kind of parallel propagating instabilities should not play a role. However, it is important to remark that, under the right conditions, the firehose instability can also be triggered in a current sheet, producing kinking of the magnetic field lines, scattering particles and reducing the temperature anisotropy 84 , in a similar way to the phenomena observed in our case.…”

Section: Ref 82 and References Therein)supporting

confidence: 73%

Instabilities of collisionless current sheets revisited: The role of anisotropic heating

2014

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In this work, we investigate the influence of the anisotropic heating on the spontaneous instability and evolution of thin Harris-type collisionless current sheets, embedded in antiparallel magnetic fields. In particular, we explore the influence of the macroparticle shape-function using a 2D version of the PIC code ACRONYM. We also investigate the role of the numerical collisionality due to the finite number of macroparticles in PIC codes. It is shown that it is appropriate to choose higher order shape functions of the macroparticles compared to a larger number of macroparticles per cell. This allows to estimate better the anisotropic electron heating due to the collisions of macroparticles in a PIC code. Temperature anisotropies can stabilize the tearing mode instability and trigger additional current sheet instabilities. We found a good agreement between the analytically derived threshold for the stabilization of the anisotropic tearing mode and other instabilities, either spontaneously developing or initially triggered ones. Numerical effects causing anisotropic heating at electron time scales, become especially important for higher mass ratios (above m i /m e = 180). If numerical effects are carefully taken into account, one can recover the theoretical estimated linear growth rates of the tearing instability of thin isotropic collisionless current sheets, also for higher mass ratios.

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Section: Ref 82 and References Therein)supporting

confidence: 73%

Instabilities of collisionless current sheets revisited: The role of anisotropic heating

2014

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“…It is known that temperature anisotropy is expected to modify the growth rate of the tearing instability [ Chen and Palmadesso , ], thus influencing the stability of current sheets and the associated magnetic reconnection activity. Preliminary numerical simulations of the coupling between microscale processes driven by temperature anisotropy and the intermediate solar wind magnetic structures [ Matteini et al ., ] suggest that fluctuations generated by kinetic instabilities (like those at work in the solar wind) play a role in regulating the stability and evolution of current sheets in anisotropic nonhomogenous plasmas. This aspect should also be addressed in more detail in the future.…”

Section: Resultsmentioning

confidence: 99%

Signatures of kinetic instabilities in the solar wind

et al. 2013

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[1] An analysis of ion non-thermal properties in the fast solar wind based on Ulysses data is reported. The radial evolution of the main proton moments (density, temperature, and drift velocities) and their empirical correlations with other plasma parameters are investigated in detail and compared with theoretical expectations. The stability of the plasma is studied against different ion kinetic instabilities driven by ion temperature anisotropies and differential velocities, focusing on the identification of possible signatures of relevant instabilities in the observed core-beam structure of proton distributions. The temperature anisotropy of the total proton distribution appears to be constrained by fire hose instabilities, in agreement with previous studies, while if considered separately, beam and core populations exhibit opposite anisotropies, with core protons characterized by perpendicular temperatures larger than the parallel ones, possibly (marginally) unstable for ion-cyclotron instability. The evolution with distance of the drift velocity between the secondary population and the main core is found to be nonadiabatic, leading to the identification of a marginal stability path of a magnetosonic ion-beam instability. As a conclusion, we find that a large fraction of the proton distributions observed by Ulysses display signatures of either a beam or a fire hose instability, suggesting that such kinetic processes play an important role in regulating the solar wind thermal energetics during the plasma expansion.

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“…The solar wind ion distribution has been assumed to be an isotropic Maxwellian. The inclusion of a temperature anisotropy would affect the reconnection rate in the current sheets, for example, due to the role of ion cyclotron or firehose instabilities, depending on whether T ⊥ > T or T ⊥ < T , respectively (Matteini et al 2013;Gingell et al 2015). The effect of using a kappa solar wind distribution on the evolution of the current sheets remains a topic for future work.…”

Section: Discussionmentioning

confidence: 99%

Multiple Current Sheet Systems in the Outer Heliosphere: Energy Release and Turbulence

Burgess

Gingell

Matteini

2016

ApJ

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In the outer heliosphere, beyond the solar wind termination shock, it is expected that the warped heliospheric current sheet forms a region of closelypacked, multiple, thin current sheets. Such a system may be subject to the ion-kinetic tearing instability, and hence generate magnetic islands and hot populations of ions associated with magnetic reconnection. Reconnection processes in this environment have important implications for local particle transport, and for particle acceleration at reconnection sites and in turbulence. We study this complex environment by means of three-dimensional hybrid simulations over long time scales, in order to capture the evolution from linear growth of the tearing instability to a fully developed turbulent state at late times. The final state develops from the highly ordered initial state via both forward and inverse cascades.Component and spectral anisotropy in the magnetic fluctuations is present when a guide field is included. The inclusion of a population of new-born interstellar pickup protons does not strongly affect these results. Finally, we conclude that reconnection between multiple current sheets can act as an important source of turbulence in the outer heliosphere, with implications for energetic particle acceleration and propagation.

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Proton Temperature Anisotropy and Magnetic Reconnection in the Solar Wind: Effects of Kinetic Instabilities on Current Sheet Stability

Cited by 25 publications

References 40 publications

Instabilities of collisionless current sheets revisited: The role of anisotropic heating

Instabilities of collisionless current sheets revisited: The role of anisotropic heating

Signatures of kinetic instabilities in the solar wind

Multiple Current Sheet Systems in the Outer Heliosphere: Energy Release and Turbulence

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