Magnetohydrodynamic turbulence in the solar wind
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Author/Creator
Author/Creator ORCID
Date
1999-11-01
Type of Work
Department
Program
Citation of Original Publication
Melvyn L. Goldstein, D. Aaron Roberts; Magnetohydrodynamic turbulence in the solar wind. Phys. Plasmas 1 November 1999; 6 (11): 4154–4160. https://doi.org/10.1063/1.873680
Rights
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0
Public Domain Mark 1.0
Subjects
Abstract
Low frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations may be thought of as originating near the Sun as nearly perfect Alfvén waves. Power spectra of these fluctuations from 10⁻⁷ Hz
to several Hz to suggest that the medium is turbulent. Near 1 AU, fluctuations below 10−⁻⁵Hz
have a relatively flat slope (∼−1)
and contain most of the energy in the fluctuating fields. From 10⁻⁵ Hz
to ∼0.1 Hz,
the spectra exhibit a power law inertial range similar to that seen in ordinary fluid turbulence. At the highest frequencies, the rapid fall-off of the power suggests that strong dissipation is occurring. From in situ measurements, it is clear that the fluctuations emanate from the solar corona. The turbulent cascade appears to evolve most rapidly in the vicinity of velocity shears and current sheets. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics in both Cartesian and spherical geometry corroborate this interpretation. There are conflicting interpretations of observations suggesting that much of the power in magnetic field fluctuations resides in quasi-two-dimensional structures and simulations have helped to elucidate some of these issues.