THE TURBULENT HEATING RATE IN STRONG MAGNETOHYDRODYNAMIC TURBULENCE WITH NONZERO CROSS HELICITY
- Space Science Center and Department of Physics, University of New Hampshire, NH (United States)
- Department of Astronomy, University of California, Berkeley, CA (United States)
- Department of Physics and Astronomy, University of Iowa, IA (United States)
- Department of Physics, University of Maryland, MD (United States)
Different results for the cascade power {epsilon} in strong, incompressible magnetohydrodynamic turbulence with nonzero cross helicity appear in the literature. In this paper, we discuss the conditions under which these different results are valid. Our conclusions can be expressed in terms of the density {rho}, the rms amplitudes z{sup +} and z{sup -} of Alfvenic fluctuations propagating parallel and antiparallel to the background magnetic field B {sub 0}, and the correlation length (outer scale) measured perpendicular to B {sub 0}, denoted L{sub perpendicular}. We argue that if z{sup +} >> z{sup -} and if the z{sup -} fluctuations are sustained by the reflection of z {sup +} fluctuations in a strong background magnetic field, then {epsilon} {approx} {rho}(z{sup +}){sup 2} z{sup -}/L{sub perpendicular} as in previous studies by Hossain, Matthaeus, Dmitruk, Lithwick, Goldreich, Sridhar, and others. On the other hand, if the minority wave type (z{sup -}) is sustained by some form of forcing that is uncorrelated with or only weakly correlated with the z{sup +} fluctuations, then {epsilon} can be much less than {rho}(z{sup +}){sup 2} z{sup -}/L{sub perpendicular}, as in previous studies by Dobrowolny, Lazarian, Chandran, and others. The mechanism for generating the minority wave type strongly affects the cascade power because it controls the coherence time for interactions between oppositely directed wave packets at the outer scale.
- OSTI ID:
- 21313640
- Journal Information:
- Astrophysical Journal, Vol. 701, Issue 1; Other Information: DOI: 10.1088/0004-637X/701/1/652; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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