Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind

Wicks, Robert T.; Horbury, T. S.; Chen, C. H. K.; Schekochihin, A. A.

doi:10.1111/j.1745-3933.2010.00898.x

Cited by 175 publications

(230 citation statements)

References 38 publications

Supporting

Mentioning

196

Contrasting

Order By: Relevance

“…In the inertial range one observes a bifurcation of the two spectra: the perpendicular spectrum follows the Kolmogorov's slope, E(k ⊥ ) ∼ k −5/3 ⊥ , while the parallel spectrum is steeper, E(k ) ∼ k −2 . This result, initially seen in fast wind measured by Ulysses (Horbury et al 2008) has been confirmed by several other studies (Podesta 2009;Luo and Wu 2010;Wicks et al 2010Chen et al 2011a). These magnetic field spectral scaling observations provide an intriguing, if not unequivocal, connection to the Goldreich-Sridhar theory (Higdon 1984;Goldreich and Sridhar 1995).…”

Section: Magnetic Fluctuationssupporting

confidence: 77%

“…Courtesy of R. Wicks. The same figure as a function of kρ i can be found in Wicks et al (2010) AU from the Sun). As the spacecraft only measures wave vectors k parallel to V sw , for small flow-to-field angles θ BV ∈ [0, 10] • , P (nT 2 /Hz) represents an E(k ) spectrum, and for quasi-perpendicular angles θ BV ∈ [80, 90] • , P ⊥ (nT 2 /Hz), is the proxy of E(k ⊥ ).…”

Section: Magnetic Fluctuationssupporting

confidence: 58%

“…However, this interpretation requires substantial turbulent energy at k ρ i ≈ 1, that is in apparent contradiction to the Goldreich-Sridhar model and to the solar wind measurements described in the following section (Horbury et al 2008;Podesta 2009;Luo and Wu 2010;Wicks et al 2010;2011;Chen et al 2011a). This is another puzzle that has important ramifications for the coronal heating problem.…”

Section: The Mhd Scale Cascadementioning

confidence: 73%

“…The method proposed by Horbury et al (2008), and used by Wicks et al (2010) in Fig. 1, is equivalent in some sense to the one used in Milano et al (2001) for numerical simulations, but can appear contradictory with the requirement of the ergodic theorem (equivalence between space and time averaging).…”

Section: Magnetic Fluctuationsmentioning

confidence: 99%

“…Precisely, in Fig. 1, Wicks et al (2010) used many hundreds of observations in each direction, so the ergodicity is met, but in a non-conventional way.…”

Section: Magnetic Fluctuationsmentioning

confidence: 99%

See 4 more Smart Citations

Solar Wind Turbulence and the Role of Ion Instabilities

et al. 2013

Self Cite

View full text Add to dashboard Cite

Solar wind is probably the best laboratory to study turbulence in astrophysical plasmas. In addition to the presence of magnetic field, the differences with neutral fluid isotropic turbulence are: (i) weakness of collisional dissipation and (ii) presence of several characteristic space and time scales. In this paper we discuss observational properties of solar wind turbulence in a large range from the MHD to the electron scales. At MHD scales, within the inertial range, turbulence cascade of magnetic fluctuations develops mostly in the plane perpendicular to the mean field, with the Kolmogorov scaling k −5/3 ⊥ for the perpendicular cascade and k −2 for the parallel one. Solar wind turbulence is compressible in nature: density fluctuations at MHD scales have the Kolmogorov spectrum. Velocity fluctuations do not follow magnetic field ones: their spectrum is a power-law with a −3/2 spectral index. Probability distribution functions of different plasma parameters are not Gaussian, indicating presence of intermittency. At the moment there is no global model taking into account all these observed properties of the inertial range. At ion scales, turbulent spectra have a break, compressibility increases and the density fluctuation spectrum has a local flattening. Around ion scales, magnetic spectra are variable and ion instabilities occur as a function of the local plasma parameters. Between ion and electron scales, a small scale turbulent cascade seems to be established. It is characterized by a well defined power-law spectrum in magnetic and density fluctuations with a spectral index close to −2.8. Approaching electron scales, the fluctuations are no more self-similar: an exponential cut-off is usually observed (for time intervals without quasi-parallel whistlers) indicating an onset of dissipation. The small scale inertial range between ion and electron scales and the electron dissipation range can be together described by ∼ k −α ⊥ exp(−k ⊥ d ), with α 8/3 and the dissipation scale d close to the electron Larmor radius d ρ e . The nature of this small scale cascade and a possible dissipation mechanism are still under debate.

show abstract

Section: Magnetic Fluctuationssupporting

confidence: 77%

Section: Magnetic Fluctuationssupporting

confidence: 58%

Section: The Mhd Scale Cascadementioning

confidence: 73%

Section: Magnetic Fluctuationsmentioning

confidence: 99%

“…Precisely, in Fig. 1, Wicks et al (2010) used many hundreds of observations in each direction, so the ergodicity is met, but in a non-conventional way.…”

Section: Magnetic Fluctuationsmentioning

confidence: 99%

See 3 more Smart Citations

Solar Wind Turbulence and the Role of Ion Instabilities

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

Dependence of solar wind speed on the local magnetic field orientation: Role of Alfvénic fluctuations

Matteini

Horbury

Neugebauer

et al. 2014

Geophysical Research Letters

117

104

View full text Add to dashboard Cite

We report an analysis of correlations between magnetic field and velocity fluctuations in the fast solar wind beyond 1 AU at high latitudes. We have found that on scales shorter than the microstream structures, there exists a well‐defined dependence of the flow speed on the angle between the magnetic field vector and the radial direction. Solar wind is found to be slightly faster when the measured magnetic field vector is transverse to the velocity, while it is always slower when the magnetic field is parallel, or antiparallel, to the radial direction. We show that this correlation is a direct consequence of the high Alfvénicity of fast wind fluctuations and that it can be reasonably described by a simple model taking into account the main properties of the low‐frequency antisunward Alfvén fluctuations as observed in the solar wind plasma. We also discuss how switchbacks, short periods of magnetic field reversals, naturally fit in this new observed correlation.

show abstract

Influence of intermittency on the anisotropy of magnetic structure functions of solar wind turbulence

Pei

Wang

et al. 2016

JGR Space Physics

View full text Add to dashboard Cite

Intermittency appears to be connected with the spectral anisotropy of solar wind turbulence. We use the Local Intermittency Measure to identify and remove intermittency from the magnetic field data measured by the Ulysses spacecraft in fast solar wind. Structure functions are calculated based on the time sequences as obtained before and after removing intermittency and arranged by time scale (τ) and ΘRB (the angle between local mean magnetic field B0 and radial direction R). Thus, the scaling exponent (ξ(p, ΘRB)) of every structure function of order (p) is obtained for different angles. Before removing intermittency, ξ(p, ΘRB) shows a distinctive dependence on ΘRB: from monofractal scaling law at ΘRB ~0° to multifractal scaling law at ΘRB ~90°. In contrast after eliminating the intermittency, ξ(p, ΘRB) is found to be more monofractal for all ΘRB. The extended structure‐function model is applied to ξ(p, ΘRB), revealing differences of its fitting parameters α (a proxy of the power spectral index) and P1 (fragmentation fraction) for the cases with and without intermittency. Parameter α shows an evident angular trend falling from 1.9 to 1.6 for the case with intermittency but has a relatively flat profile around 1.8 for the case without intermittency. Parameter P1 rises from around 0.5 to above 0.8 with increasing ΘRB for the intermittency case and is located between 0.5 and 0.8 for the case lacking intermittency. Therefore, we may infer that it is the anisotropy of intermittency that causes the scaling anisotropy of energy spectra and the unequal fragmentation of energy cascading.

show abstract

Power and spectral index anisotropy of the entire inertial range of turbulence in the fast solar wind

Abstract: 12.12.13 KB. Ok to add the published version to spiral. RAS/ OUP policy

Cited by 175 publications

References 38 publications

Solar Wind Turbulence and the Role of Ion Instabilities

Solar Wind Turbulence and the Role of Ion Instabilities

Dependence of solar wind speed on the local magnetic field orientation: Role of Alfvénic fluctuations

Influence of intermittency on the anisotropy of magnetic structure functions of solar wind turbulence

Contact Info

Product

Resources

About