Ion‐scale spectral break of solar wind turbulence at high and low beta

Chen, C. H. K.; Leung, L. Stan; Boldyrev, Stanislav; Maruca, B. A.; Bale, S. D.

doi:10.1002/2014gl062009

Cited by 163 publications

(220 citation statements)

References 68 publications

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“…Howes et al 2011;Franci et al 2015a). Note however that recent observational (Chen et al 2014) and numerical (Cerri et al 2016;Franci et al 2016) investigations suggest that the quantitative agreement with KAW predictions is fulfilled better at high ( 1) than low beta; this aspect will be the subject of a forthcoming study.…”

Section: T H E O R E T I C a L P R E D I C T I O Nmentioning

confidence: 82%

Electric and magnetic spectra from MHD to electron scales in the magnetosheath

Matteini

Alexandrova

Chen

et al. 2016

Mon. Not. R. Astron. Soc.

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We investigate the transition of the turbulence from large to kinetic scales using Cluster observations. Simultaneous spectra of magnetic and electric fields in the Earth's magnetosheath from magnetohydrodynamic (MHD) to electron scales are presented for the first time. While the two spectra have approximatively similar behaviour in the fluid-MHD regime, they show different trends in the kinetic range. As the magnetic field spectrum steepens at ion scales, the electric field spectrum is characterized by a shallower power law continuing down to electron scales. Such an evolution is consistent with theoretical expectations, assuming that the turbulence is dominated by highly oblique k-vectors and that between ion and electron scales the electric field is governed by the non-ideal terms in the generalized Ohm's law. This leads to an expected linear increase of the electric-to-magnetic ratio of fluctuations, consistent with observations presented here. The influence of local whistler wave activity on electron-scale spectra is also discussed.

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Section: T H E O R E T I C a L P R E D I C T I O Nmentioning

confidence: 82%

Electric and magnetic spectra from MHD to electron scales in the magnetosheath

Matteini

Alexandrova

Chen

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Finally, the measured ion-scale spectral break can be compared to the expected dispersive scale for the transition from Alfvénic to kinetic Alfvén turbulence. Chen et al (2014a) examined periods of extreme β i so that the various ion scales could be distinguished, and found that for β i 1 the break occurs close to the ion gyroscale (kρ i ∼ 1), which is indeed the dispersive scale for Alfvénic turbulence, but at β i 1 it occurs at the ion inertial length (kd i ∼ 1). This latter result remains to be explained, but one possibility is the presence of a significant k component in low-β i turbulence (Boldyrev et al 2015).…”

Section: Phenomenological Models Of Kinetic Range Turbulencementioning

confidence: 99%

Recent progress in astrophysical plasma turbulence from solar wind observations

2016

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This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvénic, measurements of critical balance, residual energy and three-dimensional structure are discussed, along with comparison to recent models of strong Alfvénic turbulence. At these scales, a few per cent of the energy is also in compressive fluctuations, and their nature, anisotropy and relation to the Alfvénic component is described. In the small-scale kinetic range, below the ion gyroscale, the turbulence becomes predominantly kinetic Alfvén in nature, and measurements of the spectra, anisotropy and intermittency of this turbulence are discussed with respect to recent cascade models. One of the major remaining questions is how the turbulent energy is dissipated, and some recent work on this question, in addition to future space missions which will help to answer it, are briefly discussed.

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“…Šafránková et al (2015) have shown that a transition between MHD and kinetic ranges (break 2) scales with the ion thermal gyroradius R g . On the other hand, Chen et al (2014a) argued that the characteristic length depends on the plasma β being proportional to R g in a high-beta plasma, whereas the inertial length determines the break frequency in the low-beta solar wind. Since a majority of our events occurred in the moderateor high-beta solar wind, we followed the suggestion of Šafránková et al (2015) and used the proton thermal gyroradius, R g ,computed from the propagated Wind magnetic field and the ion thermal speed, V th ,for a determination of the gyrostructure frequency, f g :…”

Section: Scaling Of Psds In Thedownstream Regionmentioning

confidence: 99%

“…A spectral break around k 1 i  » (where i  is the ion thermal gyroradius) or kd i ≈1 (where d i is the ion inertial length) marks the end of the inertial range and suggests a possible initiation of kinetic dissipation processes at ion scales, while turbulent cascade continues to operate toward smaller scales up to electron gyroradius(e.g., Alexandrova et al 2009Alexandrova et al , 2012Chen et al 2014a).…”

Section: Introductionmentioning

confidence: 99%

Density Fluctuations Upstream and Downstream of Interplanetary Shocks

Pitňa

Šafránková

Němeček

et al. 2016

ApJ

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Interplanetary (IP) shocks as typical large-scale disturbances arising fromprocesses such asstream-stream interactions or Interplanetary Coronal Mass Ejection (ICME) launching play a significant role in the energy redistribution, dissipation, particle heating, acceleration, etc. They can change the properties of the turbulent cascade on shorter scales. We focus on changes of the level and spectral properties of ion flux fluctuations upstream and downstream of fastforward oblique shocks. Although the fluctuation level increases by an order of magnitude across the shock, the spectral slope in the magnetohydrodynamic range is conserved. The frequency spectra upstream of IP shocks are the same as those in the solar wind (if not spoiled by foreshock waves). The spectral slopes downstream are roughly proportional to the corresponding slopes upstream, suggesting that the properties of the turbulent cascade are conserved across the shock;thus, the shock does not destroy the shape of the spectrum as turbulence passes through it. Frequency spectra downstream of IP shocks often exhibit "an exponential decay" in the ion kinetic range that was earlier reported at electron scales in the solar wind or at ion scales in the interstellar medium. We suggest that the exponential shape of ion flux spectra in this range is caused by stronger damping of the fluctuations in the downstream region.

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Ion‐scale spectral break of solar wind turbulence at high and low beta

Cited by 163 publications

References 68 publications

Electric and magnetic spectra from MHD to electron scales in the magnetosheath

Electric and magnetic spectra from MHD to electron scales in the magnetosheath

Recent progress in astrophysical plasma turbulence from solar wind observations

Density Fluctuations Upstream and Downstream of Interplanetary Shocks

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