Alfvénic turbulence beyond the ambipolar diffusion scale

Journal Article · Mon Jun 01 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/805/2/118· OSTI ID:22883155

Burkhart, Blakesley ^[1]; Lazarian, A. ^[2]; Balsara, D.; Meyer, C. ^[3]; Cho, J. ^[4]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 0213 (United States)
2. Astronomy Department, University of Wisconsin, Madison, 475 N. Charter St., WI 53711 (United States)
3. Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
4. Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)

We investigate the nature of the Alfvénic turbulence cascade in two-fluid magnetohydrodynamic (MHD) simulations in order to determine if turbulence is damped once the ion and neutral species become decoupled at a critical scale called the ambipolar diffusion scale (L{sub AD}). Using mode decomposition to separate the three classical MHD modes, we study the second-order structure functions of the Alfvén mode velocity field of both neutrals and ions in the reference frame of the local magnetic field. On scales greater than L{sub AD} we confirm that two-fluid turbulence strongly resembles single-fluid MHD turbulence. Our simulations show that the behavior of two-fluid turbulence becomes more complex on scales less than L{sub AD}. We find that Alfvénic turbulence can exist past L{sub AD} when the turbulence is globally super-Alfvénic, with the ions and neutrals forming separate cascades once decoupling has taken place. When turbulence is globally sub-Alfvénic and hence strongly anisotropic, with a large separation between the parallel and perpendicular decoupling scales, turbulence is damped at L{sub AD}. We also find that the power spectrum of the kinetic energy in the damped regime is consistent with a k{sup −4} scaling (in agreement with the predictions of Lazarian et al.).

• OSTI ID: 22883155
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 805; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALFVEN WAVES
AMBIPOLAR DIFFUSION
ANISOTROPY
COMPUTERIZED SIMULATION
DECOUPLING
FORECASTING
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
SPECTRA
STRUCTURE FUNCTIONS
TURBULENCE
VELOCITY