Statistical Analysis of the High‐Frequency Spectral Break of the Solar Wind Turbulence at 1 AU

Markovskii, S. A.; Vasquez, Bernard J.; Smith, Charles W.

doi:10.1086/527431

Cited by 101 publications

(75 citation statements)

References 78 publications

(107 reference statements)

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“…This scaling offers an explanation for the observed spectral kink wavenumbers, which were found to be inversely proportional to the fluctuation amplitudes at the spectral kink positions (Markovskii et al, 2008).…”

Section: Summary and Discussionmentioning

confidence: 75%

“…The spectral break f b is often associated with one of the proton kinetic scales, the proton gyroradius ρ p or the proton inertial length δ p = V A / p , such that the observed frequency of the break is 2πf b V SW /ρ p or V SW /δ p Bale et al, 2005;Alexandrova et al, 2010;Sahraoui et al, 2010). Perri et al (2010) show, however, that the break position is not sensitive to the radial dependence of the ion scales, whereas Markovskii et al (2008) argue that the break position depends upon a combination of the scale and the turbulent amplitudes at that scale.…”

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confidence: 99%

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Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Voitenko

Keyser

2011

Nonlin. Processes Geophys.

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Abstract.A weakly dispersive range (WDR) of kinetic Alfvén turbulence is identified and investigated for the first time in the context of the MHD/kinetic turbulence transition. We find perpendicular wavenumber spectra ∝ k −3 ⊥ and ∝ k −4 ⊥ formed in WDR by strong and weak turbulence of kinetic Alfvén waves (KAWs), respectively. These steep WDR spectra connect shallower spectra in the MHD and strongly dispersive KAW ranges, which results in a specific doublekink (2-k) pattern often seen in observed turbulent spectra. The first kink occurs where MHD turbulence transforms into weakly dispersive KAW turbulence; the second one is between weakly and strongly dispersive KAW ranges. Our analysis suggests that partial turbulence dissipation due to amplitude-dependent non-adiabatic ion heating may occur in the vicinity of the first spectral kink. The threshold-like nature of this process results in a conditional selective dissipation that affects only the largest over-threshold amplitudes and that decreases the intermittency in the range below the first spectral kink. Several recent counter-intuitive observational findings can be explained by the coupling between such a selective dissipation and the nonlinear interaction among weakly dispersive KAWs.

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Section: Summary and Discussionmentioning

confidence: 75%

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confidence: 99%

Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Voitenko

Keyser

2011

Nonlin. Processes Geophys.

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“…8(a). A larger statistical sample of 960 spectra shows the dependence between f b , and f λ i B δB b , where δB b /B is the relative amplitude of the fluctuations at the break scale (Markovskii et al 2008). This result is still not explained.…”

Section: Turbulence At Kinetic Scalesmentioning

confidence: 96%

Solar Wind Turbulence and the Role of Ion Instabilities

et al. 2013

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Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling k −5/3 ⊥ for the perpendicular cascade and k −2 for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a −3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to −2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by ∼ k −α ⊥ exp(−k ⊥ d ), with α 8/3 and the dissipation scale d close to the electron Larmor radius d ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.

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“…The value of the exponent of this second power-law is also variable and changes depending on plasma conditions such as magnetic energy, anisotropy of the magnetic field fluctuations with respect to the mean magnetic field and bulk plasma velocity, etc. [18][19][20]. The physics of these scales, in this sub-ion range, is still unknown and is hotly debated.…”

Section: Motivationmentioning

confidence: 99%

Dissipation and heating in solar wind turbulence: from the macro to the micro and back again

Kiyani

Osman

Chapman

2015

Phil. Trans. R. Soc. A.

178

143

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The past decade has seen a flurry of research activity focused on discerning the physics of kinetic scale turbulence in high-speed astrophysical plasma flows. By ‘kinetic’ we mean spatial scales on the order of or, in particular, smaller than the ion inertial length or the ion gyro-radius—the spatial scales at which the ion and electron bulk velocities decouple and considerable change can be seen in the ion distribution functions. The motivation behind most of these studies is to find the ultimate fate of the energy cascade of plasma turbulence, and thereby the channels by which the energy in the system is dissipated. This brief Introduction motivates the case for a themed issue on this topic and introduces the topic of turbulent dissipation and heating in the solar wind. The theme issue covers the full breadth of studies: from theory and models, massive simulations of these models and observational studies from the highly rich and vast amount of data collected from scores of heliospheric space missions since the dawn of the space age. A synopsis of the theme issue is provided, where a brief description of all the contributions is discussed and how they fit together to provide an over-arching picture on the highly topical subject of dissipation and heating in turbulent collisionless plasmas in general and in the solar wind in particular.

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Statistical Analysis of the High‐Frequency Spectral Break of the Solar Wind Turbulence at 1 AU

Cited by 101 publications

References 78 publications

Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence

Solar Wind Turbulence and the Role of Ion Instabilities

Dissipation and heating in solar wind turbulence: from the macro to the micro and back again

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