The transport of low-frequency turbulence in astrophysical flows. II. Solutions for the super-Alfvénic solar wind

Journal Article · Wed May 20 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/805/1/63· OSTI ID:22883179

Adhikari, L.; Zank, G. P.; Hu, Q. ^[1]; Bruno, R. ^[2]; Telloni, D. ^[3]; Hunana, P.; Dosch, A. ^[4]; Marino, R. ^[5]

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1. Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
2. INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy)
3. INAF—Astrophysical Observatory of Torino, Via Osservatorio 20, I-10025 Pino Torinese (Italy)
4. Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
5. National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

Zank et al. developed a turbulence transport model for low-frequency incompressible magnetohydrodynamic (MHD) turbulence in inhomogeneous flows in terms of the energy corresponding to forward and backward propagating modes, the residual energy, the correlation lengths corresponding to forward and backward propagating modes, and the correlation length of the residual energy. We apply the Zank et al. model to the super-Alfvénic solar wind i.e., |U|≫|V{sub A}| and solve the coupled equations for two cases, the first being the heliosphere from 0.29 to 5 AU with and without the Alfvén velocity, and the second being the “entire” heliosphere from 0.29 to 100 AU in the absence of the Alfvén velocity. The model shows that (1) shear driving is responsible for the in situ generation of backward propagating modes, (2) the inclusion of the background magnetic field modifies the transport of turbulence in the inner heliosphere, (3) the correlation lengths of forward and backward propagating modes are almost equal beyond ∼30 AU, and (4) the fluctuating magnetic and kinetic energies in MHD turbulence are in approximate equipartition beyond ∼30 AU. A comparison of the model results with observations for the two cases shows that the model reproduces the observations quite well from 0.29 to 5 AU. The outer heliosphere (>1 AU) observations are well described by the model. The temporal and latitudinal dependence of the observations makes a detailed comparison difficult but the overall trends are well captured by the models. We conclude that the results are a reasonable validation of the Zank et al. model for the super-Alfvénic solar wind.

• OSTI ID: 22883179
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 805; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
COMPARATIVE EVALUATIONS
CORRELATIONS
HELIOSPHERE
INCLUSIONS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MATHEMATICAL SOLUTIONS
SOLAR WIND
TRANSPORT THEORY
TURBULENCE