Majority of Solar Wind Intervals Support Ion-Driven Instabilities

Klein, K. G.; Alterman, B. L.; Stevens, M. L.; Vech, Daniel; Kasper, J. C.

doi:10.1103/physrevlett.120.205102

Cited by 69 publications

(77 citation statements)

References 38 publications

(45 reference statements)

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“…Despite these limitations, our numerical results show that fire hose instabilities coexist with plasma turbulence and generate temperature-anisotropy reducing modes that lie in the spectral space outside the region dominated by the turbulent cascade. We expect a similar behavior for other ion kinetic instabilities driven by particle temperature anisotropies and/or differential streaming in the solar wind (as indicated by in situ observations of Klein et al 2018), except possibly for the mirror instability that drives strongly oblique modes; 2-D numerical simulations show that the mirror instability coexists with plasma turbulence ). However, the present simulation results show that these 2-D results are too limited and need to be revisited.…”

Section: Discussionsupporting

confidence: 62%

“…There are indications that such instabilities are active in the solar wind. Apparent bounds on ion parameters are observed that are relatively in agreement with theoretical kinetic linear predictions (Gary et al 2001;Hellinger et al 2006;Maruca et al 2012;Matteini et al 2013;Klein et al 2018). Furthermore, wave activity driven by the kinetic instabilities associated with the ion temperature anisotropies and/or differential velocity is often observed (Jian et al 2009;Gary et al 2016;Wicks et al 2016).…”

Section: Introductionsupporting

confidence: 73%

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Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Hellinger

Matteini

Landi

et al. 2019

ApJ

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The relationship between a decaying plasma turbulence and proton fire hose instabilities in a slowly expanding plasma is investigated using three-dimensional (3-D) hybrid expanding box simulations. We impose an initial ambient magnetic field along the radial direction, and we start with an isotropic spectrum of large-scale, linearly-polarized, random-phase Alfvénic fluctuations with zero cross-helicity. A turbulent cascade rapidly develops and leads to a weak proton heating that is not sufficient to overcome the expansion-driven perpendicular cooling. The plasma system eventually drives the parallel and oblique fire hose instabilities that generate quasi-monochromatic wave packets that reduce the proton temperature anisotropy. The fire hose wave activity has a low amplitude with wave vectors quasi-parallel/oblique with respect to the ambient magnetic field outside of the region dominated by the turbulent cascade and is discernible in one-dimensional power spectra taken only in the direction quasi-parallel/oblique with respect to the ambient magnetic field; at quasi-perpendicular angles the wave activity is hidden by the turbulent background. These waves are partly reabsorbed by protons and partly couple to and participate in the turbulent cascade. Their presence reduces kurtosis, a measure of intermittency, and the Shannon entropy but increases the Jensen-Shannon complexity of magnetic fluctuations; these changes are weak and anisotropic with respect to the ambient magnetic field and it's not clear if they can be used to indirectly discern the presence of instability-driven waves. arXiv:1908.07760v1 [physics.space-ph]

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Section: Discussionsupporting

confidence: 62%

Section: Introductionsupporting

confidence: 73%

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Hellinger

Matteini

Landi

et al. 2019

ApJ

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“…The various waves analysed here also depend on other plasma parameters such as β j of all species, the number of species, relative drifts among them, and their temperature anisotropies (Marsch et al 1982b,a;Kasper et al 2002;Bale et al 2009;Maruca et al 2012;Verscharen et al 2013;Yoon 2017;Klein et al 2018). It would be useful to repeat our investigation in individual cases when using plasma models with parameters different from the representative values used in this study (Riquelme et al 2015(Riquelme et al , 2016(Riquelme et al , 2018.…”

Section: Discussionmentioning

confidence: 90%

Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio

Verscharen

Parashar

Gary

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The magnetization |Ω e |/ω e is an important parameter in plasma astrophysics, where Ω e and ω e are the electron gyro-frequency and electron plasma frequency, respectively. It only depends on the mass ratio m i /m e and the light-to-Alfvén speed ratio c/v Ai , where m i (m e ) is the ion (electron) mass, c is the speed of light, and v Ai is the ion Alfvén speed. Nonlinear numerical plasma models such as particle-in-cell simulations must often assume unrealistic values for m i /m e and for c/v Ai . Because linear theory yields exact results for parametric scalings of wave properties at small amplitudes, we use linear theory to investigate the dispersion relations of Alfvén/ion-cyclotron and fast-magnetosonic/whistler waves as prime examples for collective plasma behaviour depending on m i /m e and c/v Ai . We analyse their dependence on m i /m e and c/v Ai in quasi-parallel and quasi-perpendicular directions of propagation with respect to the background magnetic field for a plasma with β j ∼ 1, where β j is the ratio of the thermal to magnetic pressure for species j. Although their dispersion relations are largely independent of c/v Ai for c/v Ai 10, the mass ratio m i /m e has a strong effect at scales smaller than the ion inertial length. Moreover, we study the impact of relativistic electron effects on the dispersion relations. Based on our results, we recommend aiming for a more realistic value of m i /m e than for a more realistic value of c/v Ai in nonrelativistic plasma simulations if such a choice is necessary, although relativistic and sub-Debye-length effects may require an additional adjustment of c/v Ai .

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“…While this numerical method has previously been applied to hundreds of intervals from the Wind spacecraft at 1 au (Klein et al 2018), a statistical assessment of linear stability as a function of solar wind and plasma parameters requires analysis of a larger set of data. Additionally, using measurements closer to the Sun than 1 au assists the study of radial variations in inferred stability.…”

Section: Datamentioning

confidence: 99%

“…In this work, we evaluate the stability of 45,147 solar wind observations made by the Helios spacecraft, a subset of observations with a bi-Maxwellian fit for the helium (α) component described in Stansby et al (2019), using a numerical implementation of the Nyquist criterion applied to the hot plasma dispersion relation for an arbitrary number of relatively drifting bi-Maxwellian components (Klein et al 2017b). The Nyquist criterion has been previously applied to hundreds of solar wind measurements made by the Wind spacecraft at 1 au (Klein et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Kasper¹,

Bale²,

Belcher³

et al. 2019

Nature

389

299

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Wave-particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of linear stability over a large subset of Helios I and II observations of the fast solar wind using a numerical evaluation of the Nyquist stability criterion, accounting for multiple sources of free energy associated with protons and helium including temperature anisotropies and relative drifts. We find that 88% of the surveyed intervals are linearly unstable. The median growth rate of the unstable modes is within an order of magnitude of the turbulent transfer rate, fast enough to potentially impact the turbulent scale-to-scale energy transfer. This rate does not significantly change with radial distance, though the nature of the unstable modes, and which ion components are responsible for driving the instabilities, does vary. The effect of ion-ion collisions on stability is found to be significant; collisionally young wind is much more unstable than collisionally old wind, with very different kinds of instabilities present in the two kinds of wind.

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Majority of Solar Wind Intervals Support Ion-Driven Instabilities

Cited by 69 publications

References 38 publications

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Turbulence versus Fire-hose Instabilities: 3D Hybrid Expanding Box Simulations

Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

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