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

Pei, Zhongtian; He, Jiansen; Wang, Xin; Tu, Chuanyi; Marsch, E.; Wang, Linghua; Yan, Limei

doi:10.1002/2015ja021057

Cited by 19 publications

(17 citation statements)

References 55 publications

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“…In fact, they recovered spectral indices of 1.63 and 1.56 for magnetic field and velocity, respectively. A similar analysis by Pei et al (), based on the use of LIM technique (see above), confirmed the effect of intermittency on turbulence spectral anisotropy.…”

Section: On the Nature Of Intermittency Eventssupporting

confidence: 77%

Intermittency in Solar Wind Turbulence From Fluid to Kinetic Scales

Bruno

2019

Earth and Space Science

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Solar wind is a highly turbulent medium exhibiting fluctuations ranging from the solar sidereal rotation period to proton and electron gyroperiods. Their amplitudes show remarkable scalings with frequency across more than seven decades, suggesting a self‐similar nature for these fluctuations. However, these fluctuations are not globally scale invariant and require a multifractal approach. Multifractality is closely related to intermittency, a phenomenon that has been studied in the solar wind for more than three decades. We now have a rather complete picture of the nature of the most intermittent events and the radial/latitudinal dependence of this phenomenon in the heliosphere. Parallel shocks, slow mode shocks or tangential discontinuities/current sheets identified as the border between adjacent flux tubes are the most intermittent structures within the low‐frequency turbulence. It is more complicated and fascinating to understand the nature of intermittent events at kinetic scales since they are directly related to dissipative phenomena and might be the key to understanding the dissipation mechanisms in the collisionless solar wind plasma. Unfortunately, we still do not have adequate plasma observations at kinetic scales to work on, but several studies, mostly numeric, have addressed this topic suggesting that discontinuities, small‐scale current sheets, and sites which are candidates for reconnection events might be regions where dissipative phenomena are at work with consequent plasma heating and acceleration. This review is intended to provide the reader with a quick overview on the past and most recent understanding of intermittency phenomenon in the solar wind from fluid to kinetic scales.

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Section: On the Nature Of Intermittency Eventssupporting

confidence: 77%

Intermittency in Solar Wind Turbulence From Fluid to Kinetic Scales

Bruno

2019

Earth and Space Science

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“…3.3). The results are given for the total structure function obtained by summing together the structure functions of the three components of the magnetic field as, for example, in Pei et al (2016).…”

Section: Structure Function Analysismentioning

confidence: 99%

Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind

et al. 2020

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Abstract. In this work, we investigate magnetic field fluctuations in three coronal mass ejection (CME)-driven sheath regions at 1 AU, with their speeds ranging from slow to fast. The data set we use consists primarily of high-resolution (0.092 s) magnetic field measurements from the Wind spacecraft. We analyse magnetic field fluctuation amplitudes, compressibility, and spectral properties of fluctuations. We also analyse intermittency using various approaches; we apply the partial variance of increments (PVIs) method, investigate probability distribution functions of fluctuations, including their skewness and kurtosis, and perform a structure function analysis. Our analysis is conducted separately for three different subregions within the sheath and one in the solar wind ahead of it, each 1 h in duration. We find that, for all cases, the transition from the solar wind ahead to the sheath generates new fluctuations, and the intermittency and compressibility increase, while the region closest to the ejecta leading edge resembled the solar wind ahead. The spectral indices exhibit large variability in different parts of the sheath but are typically steeper than Kolmogorov's in the inertial range. The structure function analysis produced generally the best fit with the extended p model, suggesting that turbulence is not fully developed in CME sheaths near Earth's orbit. Both Kraichnan–Iroshinikov and Kolmogorov's forms yielded high intermittency but different spectral slopes, thus questioning how well these models can describe turbulence in sheaths. At the smallest timescales investigated, the spectral indices indicate shallower than expected slopes in the dissipation range (between −2 and −2.5), suggesting that, in CME-driven sheaths at 1 AU, the energy cascade from larger to smaller scales could still be ongoing through the ion scale. Many turbulent properties of sheaths (e.g. spectral indices and compressibility) resemble those of the slow wind rather than the fast. They are also partly similar to properties reported in the terrestrial magnetosheath, in particular regarding their intermittency, compressibility, and absence of Kolmogorov's type turbulence. Our study also reveals that turbulent properties can vary considerably within the sheath. This was particularly the case for the fast sheath behind the strong and quasi-parallel shock, including a small, coherent structure embedded close to its midpoint. Our results support the view of the complex formation of the sheath and different physical mechanisms playing a role in generating fluctuations in them.

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“…A cascade of energy could produce a power law spectrum of SAFPs. Critical balance cascade (Goldreich & Sridhar 1995;Schekochihin et al, 2009, Tessein et al, 2009 or intermittent structures (Luo et al, 2011;Pei et al, 2016;Wang et al, 2014Wang et al, , 2016 may generate the observed spectral anisotropy. However, the source region of SAFPs has not been identified.…”

Section: Discussionmentioning

confidence: 99%

“…This spectral index anisotropy of magnetic turbulence in the fast solar wind is found to last throughout the inner heliosphere from 0.3 AU to 1 AU (He et al, 2013). It is often considered as a signature of a cascade according to the critical balance theory (Goldreich & Sridhar, 1995;Schekochihin et al, 2009;Tessein et al, 2009) and may also be explained by the influence of intermittent structures on the solar wind turbulence (Luo et al, 2011;Pei et al, 2016;Wang et al, 2014Wang et al, , 2016. However, for the SAFPs found by Wang et al (2015) the power and spectral index anisotropy were not investigated.…”

Section: 1002/2017ja024422mentioning

confidence: 99%

A Study on Sunward Propagating Alfvénic Fluctuations With a Power Law Spectrum Observed by the Wind Spacecraft

Wang

et al. 2017

JGR Space Physics

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Sunward propagating Alfvénic fluctuations with a power law spectrum (SAFP) have been recently observed in the upstream region of the Earth's bow shock. However, some physical properties of these fluctuations such as anisotropy remain unclear. Here we develop a new method for identifying SAFPs, and present for the first time the anisotropy of SAFPs power and spectral index. In this method, the propagation direction determination of SAFPs does not rely on a radial magnetic geometry but the pitch angle distribution of strahl electron outflow. Therefore, the SAFPs with any value of θRB (angle between the global mean magnetic field and the Sun‐to‐Earth radial direction) can be identified, so that enables the study of the spectral anisotropy. We find 508 SAFPs using the Wind spacecraft measurements from 1995 to 2014. We show that the SAFP has an averaged spectral index of −1.77 ± 0.28 and the index changes continuously from −2.18 ± 0.21 when θRB=0°–10° to −1.71 ± 0.03 when θRB=80°–90°. These SAFPs are observed more frequently in the slow solar wind especially at solar minimum. We also select antisunward propagating Alfvénic fluctuations with a power law spectrum using the same method for comparison. The results indicate that the power spectrum of SAFP is steeper, and the spectral intensity as well as the power anisotropy of SAFP is weaker. These new findings may provide information on the generation of turbulence in the upstream region.

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

Cited by 19 publications

References 55 publications

Intermittency in Solar Wind Turbulence From Fluid to Kinetic Scales

Intermittency in Solar Wind Turbulence From Fluid to Kinetic Scales

Magnetic field fluctuation properties of coronal mass ejection-driven sheath regions in the near-Earth solar wind

A Study on Sunward Propagating Alfvénic Fluctuations With a Power Law Spectrum Observed by the Wind Spacecraft

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