Weakly Compressible Magnetohydrodynamic Turbulence in the Solar Wind and the Interstellar Medium

Bhattacharjee, A.; Ng, C. S.; Spangler, S. R.

doi:10.1086/305184

Cited by 92 publications

(75 citation statements)

References 29 publications

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“…For such magnetic pressure-driven density fluctuations, our parameter would be a poor estimator of the amplitude of magnetic and velocity fluctuations. However, Bhattacharjee et al (1998) found that if the background plasma contained even relatively small spatial inhomogeneity, the pressure fluctuations were more significant and proportional to the amplitude of the magnetic fluctuations (see Fig. 6 of that paper).…”

Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 91%

“…Theoretically, Bhattacharjee, Ng, & Spangler (1998) considered the nature of pressure and density fluctuations in compressible MHD, utilizing a theoretical framework termed the '' four-field equations.'' In this theory, density fluctuations are linearly proportional to the pressure fluctuations.…”

Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 99%

“…The second argument is observational and served as the inspiration for the theoretical work of Bhattacharjee et al (1998). A number of investigations have utilized the Helios spacecraft data set to study the dependence of pressure or density fluctuations on velocity and magnetic field fluctuations (Tu & Marsch 1994;Klein et al 1993).…”

Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 99%

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The Amplitude of Magnetohydrodynamic Turbulence in the Inner Solar Wind

Spangler

2002

ApJ

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Recent radio wave interplanetary scintillation observations have improved our knowledge of the level of turbulent fluctuations of plasma density in the inner solar wind at heliocentric distances of 16-26 R and less accurately outside this range. This information relates to fluctuations in the inertial subrange of the turbulence. Of particular concern in this paper is the heliocentric distance dependence of the power-law normalization parameter C 2 N . This measurement of C 2 N , when combined with independent measurements of the mean plasma density in the inner solar wind, indicates that the dimensionless amplitude of the turbulence n =n n is low, of the order of 6%-15%, where n is the standard deviation of the density fluctuations and n n is the mean value. The deduced value for depends on an assumed value for the outer scale of the turbulence, l o . I adopt a fiducial value of l o ¼ 1 R . A comparison is made with independent estimates of , from both radio remote sensing in the same part of space and in situ measurements at greater distances. Satisfactory agreement occurs. I discuss the possibility that this dimensionless density amplitude might be a proxy for the corresponding amplitude of the magnetic field fluctuations. This is a controversial assertion. However, if it is the case, the measurements suggest that the turbulence in the inner solar wind is weak, in the sense of being dynamically and thermodynamically important.

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Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 91%

Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 99%

Section: Theoretical Results On Evolution Of the Outer Scalementioning

confidence: 99%

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The Amplitude of Magnetohydrodynamic Turbulence in the Inner Solar Wind

Spangler

2002

ApJ

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“…Furthermore, we have calculated energy spectra, not density fluctuation spectra. It is often assumed that density fluctuations are enslaved to energy fluctuations, but this is not necessarily so [46,49]. In future work, we will attempt to remedy some of these limitations.…”

Section: Resultsmentioning

confidence: 99%

“…Then the nonlinear MHD equations can be reduced rigorously to the so-called reduced MHD (RMHD) [44][45][46] Recent work has demonstrated conclusively that weak MHD turbulence in the presence of a uniform magnetic field is dominated by three-wave interactions that mediate the collisions of shear-Alfvén wave packets [31][32][33]. Using the ideal RMHD equations, Ng and Bhattacharjee (NB) calculate in closed form the three-wave and four-wave interaction terms, and show the former to be asymptotically dominant if the wave packets have non-zero || 0 k = components.…”

Section: Random Three-wave Interactions and The Anisotropic Spectrummentioning

confidence: 99%

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind

Bhattacharjee¹,

2003

AIP Conference Proceedings

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Abstract.A theoretical model is given of anisotropic magnetohydrodynamic turbulence in the interstellar medium and the solar wind. The model is motivated by observations that show significant deviations from the Kolmogorov powerlaw. Dimensional and heuristic arguments are given and critically assessed. On the basis of the weak turbulence approximation in which three-wave interactions dominate, analytical and numerical results are obtained for the anisotropic energy spectrum produced by the random scattering of shear Alfvén waves propagating parallel to a largescale magnetic field. The energy spectrum is shown to be proportional to 2 k − ⊥ , qualitatively consistent with some observations and wave kinetic theory.

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A conservative pressure‐correction method for the Euler and ideal MHD equations at all speeds

Heul

Vuik

Wesseling

2002

Numerical Methods in Fluids

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SUMMARYTo e ciently compute weakly compressible magnetohydrodynamic ows in astrophysical applications, approximate low Mach number reduced forms of the compressible MHD equations are frequently used. This is because standard characteristic-based schemes for the full compressible MHD equations are ine cient and inaccurate for computing low Mach number magnetohydrodynamic ow, as a result of the increasing sti ness and weakening pressure=density coupling of the equations when M ↓ 0. Furthermore, these schemes are colocated, so that additional and artiÿcial measures have to be taken to ensure solenoidality of the magnetic ÿeld. We present a new method with a staggered spatial discretization and a pressure-correction solution algorithm that is more suitable for computing weakly compressible MHD ow, because of its Mach-uniformity and e cient and accurate handling of the solenoidality constraint on the magnetic ÿeld.

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Weakly Compressible Magnetohydrodynamic Turbulence in the Solar Wind and the Interstellar Medium

Cited by 92 publications

References 29 publications

The Amplitude of Magnetohydrodynamic Turbulence in the Inner Solar Wind

The Amplitude of Magnetohydrodynamic Turbulence in the Inner Solar Wind

Anisotropic MHD Turbulence in the Interstellar Medium and Solar Wind

A conservative pressure‐correction method for the Euler and ideal MHD equations at all speeds

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