Generation of anisotropic turbulence in drifting proton-alpha plasmas Yana Maneva, S. Poedts CmPA, KU Leuven In collaboration with: A. Viñas and L. NASA/CUA

Obs.: Bruno+ 1985, 2013, Leamon+ 1999, Podesta 2007, Alexandrova+ 2012, Sahraoui+ 2010, Salem+ 2012, Kiyani+ 2015, Lyon+ 2016; Jian+ 2009, 2014; He+ 2012,… Interstellar magnetic field at 1 AU: multiple spectral breaks in the B field power density slope Turbulent cascade in w/k with decreasing spectral index Cluster Simulations: Howes et al. 2013; Hunana et al. 2013, 2016; Meriyand 2015,2016; Vallentini et al. 2015; Servidio et al. 2015; Franci 2015; Califano 2014; Verdini 2015; Pucci 2015, … Wind

Alexandrova et al., Sp. Sci. Rev Possible fitting of the observed magnetic field power spectra with exponential decay instead of separate slopes

Wicks et al. 2010; Alexandrova et al., 2013 Evolution of the parallel and perpendicular magnetic power spectra

Reconstruction of the initial magnetic field spectra for parallel propagating fluctuations Viñas et al., ApJ 2014 Conserved div B = 0, magnetic helicity and energy Parseval’s theorem

Generation of obliquely propagating magnetic fluctuations by rotation of the parallel spectra in Fourier space Maneva et al., ApJ 2015

Initial conditions for the simulations – modeled magnetic field spectra and plasma parameters based on Wind data Maneva et al. 2015a Maneva et al. 2015b

V αp = 0V A Vαp = 0.2VA Vαp = 0.5VA Vαp = 0VA Vαp = 0.2VA Vαp = 0.5VA Velocity and Magnetic field fluctuations typical for Alfvén waves proton s V αp = 0V A Vαp = 0.2VA Vαp = 0.5VA Vαp = 0VA Vαp = 0.2VA Vαp = 0.5VA Velocity and Magnetic field fluctuations typical for Alfvén waves proton s V αp = 0V A Vαp = 0.2VA Vαp = 0.5VA Vαp = 0VA Vαp = 0.2VA Vαp = 0.5VA Velocity and Magnetic field fluctuations typical for Alfvén waves proton s alphas Maneva et al. 2015a

V αp = 0V A V αp = 0.2V A Generation of oblique waves and transfer of magnetic energy depending on the relative drift speed

Vαp=0V A Vαp=0.2V A Maneva et al., A&A 2015

Magnetic field power spectrum in Fourier space Generation of oblique waves with perpendicular wave numbers, k y, from the initial parallel spectrum within the preset range of k x

Evolution of the initial magnetic field energy spectra with steepening of the spectral slope 0 deg. initial 0 deg. late K parallel 30 deg. K parallel 30 deg. late

Evolution of the magnetic power in perpendicular direction for wave propagation at 30 degrees

60 deg. perp. initial 60 deg. perp. late 60 deg. parallel initial 60 deg. parallel late

30 degrees Temporal evolution of the parallel magnetic power spectra

Temporal evolution of the perpendicular magnetic power spectra 30 degrees

Evolved 2D B Field Fluctuations starting with parallel wave spectra (at 0°) – generation of || B field, associated with oblique waves

Conclusions:  We studied the kinetic dissipation and anisotropic evolution of turbulent spectra of parallel and oblique Alfvén-cyclotron waves  The energy cascade in parallel and perpendicular direction depend strongly on the plasma parameters and the initial wave spectral slopes – relative drifts facilitate transport in parallel direction and suppress energy transport in perpendicular direction Within our case studies the parallel component of the magnetic field spectra obtains a steeper slope and decays faster than the perpendicular one, as observed in SW  Further studies are needed to study the nature of the anisotropic cascade and its dependence on the fluctuation scales and plasma properties, such as temperature, temperature anisotropies, etc.

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