Evolution of anisotropic turbulence in the fast and slow solar wind: Theory and Solar Orbiter measurements

ORAL

Abstract

Solar Orbiter (SolO) was launched on February 9, 2020, allowing us to study the nature of turbulence in the inner heliopshere. We investigate the evolution of anisotropic turbulence in the fast and slow solar wind in the inner heliosphere using the nearly incompressible magnetohydrodynamic (NI MHD) turbulence model and SolO measurements. We calculated the two dimensional (2D) and the slab variances of the energy in forward and backward propagating modes, the fluctuating magnetic energy, the fluctuating kinetic energy, the normalized residual energy, and the normalized cross-helicity as a function of the angle between the mean solar wind speed and the mean magnetic field θ_UB, and as a function of the heliocentric distance using SolO measurements. We compared the observed results and the theoretical results of the NI MHD turbulence model as a function of the heliocentric distance. The results show that the ratio of 2D energy and slab energy of forward and backward propagating modes, magnetic field fluctuations, and kinetic energy fluctuations increases as the angle between the mean solar wind flow and the mean magnetic field increases from θ_UB=0 deg to approximately θ_UB=90 deg and then decreases as θ_UB -> 180 deg. We find that solar wind turbulence is a superposition of the dominant 2D component and a minority slab component as a function of the heliocentric distance. We find excellent agreement between the theoretical results and observed results as a function of the heliocentric distance.

*We acknowledge the partial support of a Parker Solar Probe contract SV4-84017, an NSF EPSCoR RII-Track-1 cooperative agreement OIA-1655280, and a NASA award 80NSSC20K1783.

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Presenters

  • Laxman Adhikari

    • The University of Alabama in Huntsville
    • University of Alabama in Huntsville
    • The university of Alabama in Huntsville
    • Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899, USA
    • Center for Space Plasma and Aeronomic Research (CSPAR) University of Alabama in Huntsville Huntsville, AL 35805, USA

Authors

  • Laxman Adhikari

    • The University of Alabama in Huntsville
    • University of Alabama in Huntsville
    • The university of Alabama in Huntsville
    • Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899, USA
    • Center for Space Plasma and Aeronomic Research (CSPAR) University of Alabama in Huntsville Huntsville, AL 35805, USA

  • Gary P Zank

    • University of Alabama in Huntsville
    • Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899, USA
    • University of Alabama-Huntsville

  • Lingling Zhao

    • University of Alabama in Huntsville
    • The University of Alabama in Huntsville
    • Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899, USA
    • Center for Space Plasma and Aeronomic Research (CSPAR) University of Alabama in Huntsville Huntsville, AL 35805, USA

  • Danielle Telloni

    • INAF Astrophysical Observatory of Torino
    • National Institute for Astrophysics—Astrophysical Observatory of Torino Via Osservatorio 20, I-10025 Pino Torinese, Italy

  • Tim Horbury

    • Imperial College London
    • Department of Physics, The Blackett Laboratory, Imperial College London, London, UK

  • Helen O’Brien

    • Department of Physics, The Blackett Laboratory, Imperial College London, London, UK

  • Vincent Evans

    • Department of Physics, The Blackett Laboratory, Imperial College London, London, UK

  • Chris J Owen

    • Mullard Space Science Laboratory, University College London, Holmbury St. Mary, UK

  • Philippe Louarn

    • Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse Université de Toulouse, CNRS 5 UMR5277, France

  • Andrei Fedorov

    • Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse Université de Toulouse, CNRS 5 UMR5277, France