Small-Scale Energy Cascade of the Solar Wind Turbulence

By O. Alexandrova, V. Carbone, P. Veltri, L. Sorriso-Valvo. 2007

262 citations recorded by the source corpus.

Magnetic fluctuations in the solar wind are distributed according to Kolmogorov’s power law f−5/3 below the ion cyclotron frequency fci. Above this frequency, the observed steeper power law is usually interpreted in two different ways, as a dissipative range of the solar wind turbulence, or another turbulent cascade, the nature of which is still an open question. Using the Cluster magnetic data we show that after the spectral break the intermittency increases toward higher frequencies, indicating the presence of nonlinear interactions inherent to a new inertial range and not to the dissipative range. At the same time the level of compressible fluctuations rises. We show that the energy transfer rate and intermittency are sensitive to the level of compressibility of the magnetic fluctuations within the small-scale inertial range. We conjecture that the time needed to establish this inertial range is shorter than the eddy-turnover time, and is related to dispersive effects. A simple phenomenological model, based on the compressible Hall MHD, predicts the magnetic spectrum ~k−7/3 + 2α, which depends on the degree of plasma compression α.

Subfields: Astronomy and Astrophysics, Computational Mechanics

View Paper: https://www.semanticscholar.org/paper/6b361b21dc80c20b4b11808a5e8421eac86a8f99

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Citations in the corpus

A Model of Turbulence in Magnetized Plasmas: Implications for the Dissipation Range in the Solar Wind (2007, background): “One recent paper [ Alexandrova et al., 2008 ] shows search coil measurements of magnetic field spectra up to 10 Hz, a factor of 20 in frequency above the breakpoint; for the 57-min interval of the fast solar wind studied, the dissipation range spectrum shows neither an exponential roll-off nor evide”
ASTROPHYSICAL GYROKINETICS: KINETIC AND FLUID TURBULENT CASCADES IN MAGNETIZED WEAKLY COLLISIONAL PLASMAS (2007, methodology): “In the magnetosheath, where the dissipation-range scales are easier tom asure than in the solar wind, recent analysis by Sahraoui et al. (2006); Alexandrova et al. (2008b) does show evidence of strong anisotropy.”
Solar Wind Turbulence and the Role of Ion Instabilities (2013, background): “One of the important properties of the transition range is that the turbulent fluctuations become more compressible here (Leamon et al. 1998; Alexandrova et al. 2008; Hamilton et al. 2008; Turner et al. 2011; Salem et al. 2012; Kiyani et al. 2013).”
ENHANCED MAGNETIC COMPRESSIBILITY AND ISOTROPIC SCALE INVARIANCE AT SUB-ION LARMOR SCALES IN SOLAR WIND TURBULENCE (2010, methodology): “This result showing an enhanced level of magnetic compressibility was repeated with a large set of ACE spacecraft data intervals (Hamilton et al. 2008) and also in much higher cadence data from the Cluster spacecraft (Alexandrova et al. 2008).”
Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind (2010, background): “The fluctuations (with respect to the large-scale mean field) of the parallel and perpendicular components of the magnetic field scale differently from large (Nicol et al. 2009) to small scales (Alexandrova et al. 2008; Sahraoui et al. 2009).”