Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Good, Simon; Ala‐Lahti, Matti; Palmerio, Erika; Kilpua, Emilia; Osmane, Adnane

doi:10.3847/1538-4357/ab7fa2

Cited by 30 publications

(64 citation statements)

References 44 publications

(64 reference statements)

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“…This is in contrast with the sheath analysed by Good et al (2020), who found clear differences between the solar wind ahead and in the sheath at the orbit of Mercury, but not near the orbit of Earth. However, they investigated fluctuations throughout the sheath collectively, while we have investigated three sub-regions separately.…”

Section: Discussioncontrasting

confidence: 98%

“…. In all instances, it can be seen that compressibility generally decreases from the smallest scales until about 100 s. This is a well known trend from previous solar wind studies (e.g., Chen et al, 2015;Matteini et al, 2018;Good et al, 2020). We note that the increase for the few highest timescales could be related to statistical errors in the data as discussed above.…”

Section: Compressibilitysupporting

confidence: 80%

“…As is to be expected considering the field compression at the shock, δB are considerably higher in the Near-Shock region than in the preceding solar wind for all events and timescales. The δB/B are also higher in the Near-Shock and Mid-Sheath regions than in the solar wind ahead, also reported in Good et al (2020). This suggests that the transition from the solar wind to the sheath generates new and/or enhances pre-existing magnetic field fluctuations at all timescales.…”

Section: Distributions and Averages Of Magnetic Field Fluctuationssupporting

confidence: 61%

“…This is consistent with sheaths being heliospheric structures that gather over long periods of time (up to several days near Earth's orbit) from inhomogeneous solar wind plasma that gets compressed and processed at the CME shock and then piles up at the ejecta leading edge. Good et al (2020) also found an increase in intermittency for their slow CME sheath from Mercury's to Earth's orbit. The authors suggested that it likely is due to the development of intermittent structures, e.g.…”

Section: Discussionmentioning

confidence: 81%

“…Detailed studies of magnetic field fluctuations in sheaths are also expected to yield new insight into outstanding problems in turbulence research, such as how intermittency in turbulence is related to the formation of coherent structures and discontinuities (e.g., current sheets) in plasmas. Good et al (2020) investigated the radial evolution of magnetic field fluctuations for a CME-driven sheath using almost radially aligned observations made by MESSENGER at ∼0.5 AU and STEREO-B at ∼1 AU. At ∼0.5 AU, where the leadingedge shock was quasi-parallel, the downstream sheath plasma developed a range of large-angle field rotations, discontinuities and complex structure that were absent in the upstream wind, with a corresponding steepening of the inertial-range spectral slope and increase in mean fluctuation compressibility in the sheath.…”

Section: Introductionmentioning

confidence: 99%

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

Kilpua¹,

Fontaine²,

Good³

et al. 2020

Preprint

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Abstract. In this work, we investigate the 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 and fluctuation amplitudes normalised to the mean magnetic field, compressibility, and spectral properties of fluctuations. We also analyse intermittency using various approaches: we apply the partial variance of increments (PVI) 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 in the sheath and in the solar wind ahead of it, each 1 hr 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 much better fit with the extended p-model (Kraichnan's form) than with the standard version, implying that turbulence is not fully developed in CME sheaths near Earth's orbit. The p-values obtained (p~0.8–0.9) also suggest relatively high intermittency. At the smallest timescales investigated, the spectral indices indicate relatively shallow slopes (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. Regarding many properties (e.g., spectral indices and compressibility) turbulent properties in sheaths, regardless their speed, resemble that of the slow wind, rather fast wind. They are also partly similar to properties reported in 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 in particular 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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Section: Discussioncontrasting

confidence: 98%

Section: Compressibilitysupporting

confidence: 80%

Section: Distributions and Averages Of Magnetic Field Fluctuationssupporting

confidence: 61%

Section: Discussionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Kilpua¹,

Fontaine²,

Good³

et al. 2020

Preprint

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Nonlinear dynamics in space plasma turbulence: temporal stochastic chaos

Chian

Borotto

Hada

et al. 2022

Rev. Mod. Plasma Phys.

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Intermittent turbulence is key for understanding the stochastic nonlinear dynamics of space, astrophysical, and laboratory plasmas. We review the theory of deterministic and stochastic temporal chaos in plasmas and discuss its link to intermittent turbulence observed in space plasmas. First, we discuss the theory of chaos, intermittency, and complexity for nonlinear Alfvén waves, and parametric decay and modulational wave–wave interactions, in the absence/presence of noise. The transition from order to chaos is studied using the bifurcation diagram. The following two types of deterministic intermittent chaos in plasmas are considered: type-I Pomeau–Manneville intermittency and crisis-induced intermittency. The role of structures known as chaotic saddles in deterministic and stochastic chaos in plasmas is investigated. Alfvén complexity associated with noise-induced intermittency, in the presence of multistability, is studied. Next, we present evidence of magnetic reconnection and intermittent magnetic turbulence in coronal mass ejections in the solar corona and solar wind via remote and in situ observations. The signatures of turbulent magnetic reconnection, i.e., bifurcated current sheet, reconnecting jet, parallel/anti-parallel Alfvénic waves, and spiky dynamical pressure pulse, as well as fully developed turbulence, are detected at the leading edge of an interplanetary coronal mass ejection and the interface region of two merging interplanetary magnetic flux ropes. Methods for quantifying the degree of coherence, amplitude–phase synchronization, and multifractality of nonlinear multiscale fluctuations are discussed. The stochastic chaotic nature of Alfvénic intermittent structures driven by magnetic reconnection is determined by a complexity–entropy analysis. Finally, we discuss the relation of nonlinear dynamics and intermittent turbulence in space plasmas to similar phenomena observed in astrophysical and laboratory plasmas, e.g., coronal mass ejections and flares in the stellar-exoplanetary environment and Galactic Center, as well as chaos, magnetic reconnection, and intermittent turbulence in laser-plasma and nuclear fusion experiments.

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Spatial Coherence of Interplanetary Coronal Mass Ejection Sheaths at 1 AU

et al. 2020

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The longitudinal spatial coherence near 1 AU of the magnetic field in sheath regions driven by interplanetary coronal mass ejection (ICME) is studied by investigating ACE and Wind spacecraft measurements of 29 sheaths. During 2000-2002 Wind performed prograde orbits, and the non-radial spacecraft separation varied from 0.001 to 0.012 AU between the studied events. We compare the measurements by computing the Pearson correlation coefficients for the magnetic field magnitude and components and estimate the magnetic field coherence by evaluating the scale lengths that give the extrapolated distance of zero correlation between the measurements. The correlation is also separately examined for low-and high-pass filtered data. We discover magnetic fields in ICME sheaths have scale lengths that are larger than those reported in the solar wind but that, in general, are smaller than the ones of the ICME ejecta. Our results imply that magnetic fields in the sheath are more coherently structured and well correlated compared to the solar wind. The largest sheath coherence is reported in the GSE y-direction that has the scale length of 0.149 AU while the lengths for B x , B z , and |B| vary between 0.024 and 0.035 AU. The same sheath magnitude ordering of scale lengths also apply for the low-pass filtered magnetic field data. We discuss field line draping and the alignment of preexisting discontinuities by the shock passage giving reasoning for the observed results.

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Radial Evolution of Magnetic Field Fluctuations in an Interplanetary Coronal Mass Ejection Sheath

Cited by 30 publications

References 44 publications

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

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

Nonlinear dynamics in space plasma turbulence: temporal stochastic chaos

Spatial Coherence of Interplanetary Coronal Mass Ejection Sheaths at 1 AU

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