A Model of Turbulence in Magnetized Plasmas: Implications for the Dissipation Range in the Solar Wind

By Gregory G. Howes, S. Cowley, William Dorland, Gregory W. Hammett, E. Quataert, A. Schekochihin. 2007

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This paper studies the turbulent cascade of magnetic energy in weakly col- lisional magnetized plasmas. A cascade model is presented, based on the assumptions of local nonlinear energy transfer in wavenumber space, critical balance between linear propagation and nonlinear interaction times, and the applicability of linear dissipation rates for the nonlinearly turbulent plasma. The model follows the nonlinear cascade of energy from the driving scale in the MHD regime, through the transition at the ion Lar- mor radius into the kinetic Alfven wave regime, in which the turbulence is dissipated by kinetic processes. The turbulent fluctuations remain at frequencies below the ion cy- clotron frequency due to the strong anisotropy of the turbulent fluctuations, kk ≪ k⊥ (implied by critical balance). In this limit, the turbulence is optimally described by gy- rokinetics; it is shown that the gyrokinetic approximation is well satisfied for typical slow solar wind parameters. Wave phase velocity measurements are consistent with a kinetic Alfven wave cascade and not the onset of ion cyclotron damping. The conditions under which the gyrokinetic cascade reaches the ion cyclotron frequency are established. Cas- cade model solutions imply that collisionless damping provides a natural explanation for the observed range of spectral indices in the dissipation range of the solar wind. The dis- sipation range spectrum is predicted to be an exponential fall off; the power-law behav- ior apparent in observations may be an artifact of limited instrumental sensitivity. The cascade model is motivated by a programme of gyrokinetic simulations of turbulence and particle heating in the solar wind.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/009636137148198eee39937e218cd0ca9609caaa

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Citations in the corpus

Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath (2016, background): “These features can be interpreted as a cascade of kinetic Alfvén turbulence from ion to electron scales (Howes et al. 2008; Schekochihin et al. 2009; Chen et al. 2010b; Boldyrev & Perez 2012).”
DEPENDENCE OF SOLAR-WIND POWER SPECTRA ON THE DIRECTION OF THE LOCAL MEAN MAGNETIC FIELD (2009, background): “…fluctuations makes a transition from an Alfvén wave cascade to a kinetic Alfvén wave (KAW) cascade at the perpendicular wavenumber k⊥ρi 1 (Quataert 1998; Quataert & Gruzinov 1999; Leamon et al. 1999; Cranmer & van Ballegooijen 2003; Howes 2008; Howes et al. 2008; Schekochihin et al. 2008, 2007).”
Recent progress in astrophysical plasma turbulence from solar wind observations (2016, background): “It was proposed (e.g., Leamon et al. 1998; Howes et al. 2008; Schekochihin et al. 2009; Boldyrev & Perez 2012), however, that Alfvénic turbulence at large scales transitions to kinetic Alfv́en turbulence at sub-ion scales, rather than whistler/EMHD turbulence, reflecting the fact that the kinetic Al”