OBSERVATIONS OF ANISOTROPIC SCALING OF SOLAR WIND TURBULENCE

Journal Article · Sat May 01 04:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/714/1/L138· OSTI ID:21448958

Luo, Q Y

Using high-speed solar wind data recorded by the Ulysses spacecraft, we investigate and estimate the anisotropic inertial range scaling of the interplanetary magnetic field. We apply the method of the magnetic structure function (MSF), S{sup n} ({tau}) = (|b(t + {tau}) - b(t)| {sup n}) {proportional_to} {tau}{sup {zeta}(n)}, to analyze the scaling of solar wind turbulence over the range from 1 s to 10{sup 4} s. By sorting the fluctuations according to the direction of the local mean magnetic field, we obtain a second-order structure function in (r, {Theta}) coordinates that reveals the scale-dependent anisotropy of the power spectrum. The scale-dependent anisotropy of the MSF indicates that the fluctuation energy tends to cascade toward the direction perpendicular to the local field. The dependence of the MSF scaling index {zeta} on the direction of the local field is found to be similar to that reported in Horbury et al. and Podesta, with {zeta}{sub perpendicular} = 0.53 {+-} 0.18 and {zeta}{sub ||} = 1.00 {+-} 0.14. Furthermore, we estimate and find the scaling law between the perpendicular and parallel scales r {sub ||} {proportional_to} r {sup 0.614} {sub perpendicular}, which implies the elongation along the parallel direction as the turbulence eddy evolves toward the small lengthscales. These results are in agreement with the predictions of magnetohydrodynamic turbulence theory.

• OSTI ID: 21448958
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 714; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
FLUID MECHANICS
FUNCTIONS
HYDRODYNAMICS
INTERPLANETARY MAGNETIC FIELDS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
SCALING LAWS
SOLAR ACTIVITY
SOLAR WIND
STELLAR ACTIVITY
STELLAR WINDS
STRUCTURE FUNCTIONS
TURBULENCE