Solar Wind Current Sheets: MVA Inaccuracy and Recommended Single‐Spacecraft Methodology

Wang, R.; Vasko, I. Y.; Phan, T. D.; Mozer, F. S.

doi:10.1029/2023ja032215

Cited by 4 publications

(9 citation statements)

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“…The early studies missed a substantial fraction of CSs present at 1 AU, because the selection procedures were based on magnetic field measurements of low temporal resolution and biased to CSs with larger thickness. The recent analyses have also revealed scaledependent properties of solar wind CSs (Vasko et al, 2022;Wang et al, 2024), which along with other arguments (Greco et al, 2008(Greco et al, , 2009Zhdankin et al, 2012) indicate that most of these structures are produced by turbulence. Solar wind CSs can provide substantial contribution into magnetic field turbulence spectra and affect the break scale between inertial and sub-ion turbulence ranges (Borovsky & Burkholder, 2020;Borovsky & Podesta, 2015).…”

Section: Introductionmentioning

confidence: 73%

“…Multi-spacecraft observations at 1 AU showed that CSs in the solar wind can be considered locally planar structures frozen into local plasma flow (Burlaga & Ness, 1969;Horbury et al, 2001;Knetter et al, 2004;Wang et al, 2024). These analyses demonstrated that the magnetic field component along the normal to a CS is typically much smaller than local magnetic field magnitude, hardly measurable even using multiple spacecraft.…”

Section: Methodsmentioning

confidence: 99%

“…These analyses demonstrated that the magnetic field component along the normal to a CS is typically much smaller than local magnetic field magnitude, hardly measurable even using multiple spacecraft. The most accurate single-spacecraft estimate of the normal is therefore delivered by the cross-product of magnetic fields at the CS boundaries (Knetter et al, 2004;Wang et al, 2024). The single-spacecraft methodology based on the cross-product normal and frozen-in assumption used previously for the analysis of magnetic reconnection and CSs at 0.2 and 1 AU (Eriksson et al, 2022;Lotekar et al, 2022;Mistry et al, 2017;Phan et al, 2010Phan et al, , 2020Vasko et al, 2021) has been recently shown to actually deliver accurate estimates of the CS thickness and current density (Wang et al, 2024).…”

Section: Methodsmentioning

confidence: 99%

“…The early studies were heavily focused on classifying CSs in terms of tangential and rotational discontinuities based on the magnetic field component along the normal computed by Minimum Variance Analysis (MVA). Multispacecraft observations showed however that MVA is typically not reliable in estimating the normal to solar wind CSs and showed that the normal magnetic field component is often within the methodology uncertainty and much smaller than local magnetic field magnitude (Horbury et al, 2001;Knetter et al, 2004;Wang et al, 2024). The latter implies that the normal is often almost perpendicular to local background magnetic field in accordance with early theoretical reasoning (Bieber et al, 1996;Leamon et al, 1998Leamon et al, , 2000Matthaeus et al, 1990).…”

Section: Introductionmentioning

confidence: 92%

“…Substantial progress has been achieved by the analysis of CSs at 1 AU using magnetic field measurements with the temporal resolution of 1/3-1/22 s (Borovsky & Burkholder, 2020;Borovsky & Podesta, 2015;Perri et al, 2012;Perrone et al, 2017;Podesta, 2017;Vasko et al, 2021Vasko et al, , 2022Vasquez et al, 2007;Wang et al, 2024). It has been shown that solar wind CSs are much more abundant than reported in the early studies, their average occurrence rate is about 10 per hour, while the half-thickness is typically about 100 km or one proton inertial length (Vasko et al, 2021(Vasko et al, , 2022Vasquez et al, 2007;Wang et al, 2024). The early studies missed a substantial fraction of CSs present at 1 AU, because the selection procedures were based on magnetic field measurements of low temporal resolution and biased to CSs with larger thickness.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

Vasko,

Alimov,

Phan

et al. 2024

JGR Space Physics

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We present statistical analysis of 16,903 current sheets (CSs) observed over 641 days aboard Ulysses spacecraft at 5 AU. We show that the magnetic field rotates across CSs through some shear angle, while only weakly varies in magnitude. The CSs are typically asymmetric with statistically different, though only by a few percent, magnetic field magnitudes at the CS boundaries. The data set is classified into about 90.6% non‐bifurcated and 9.4% bifurcated CSs. Most of the CSs are proton kinetic‐scale structures with the half‐thickness of non‐bifurcated and bifurcated CSs within respectively 200–2,000 km and 500–5,000 km or 0.5–5λp and 0.7–15λp in units of local proton inertial length. The amplitude of the current density, mostly parallel to magnetic field, is typically within 0.05–0.5 nA/m2 or 0.04–0.4JA in units of local Alfvén current density. The CSs demonstrate approximate scale‐invariance with the shear angle and current density amplitude scaling with the half‐thickness, and . The matching of the magnetic field rotation and compressibility observed within the CSs against those in ambient solar wind indicate that the CSs are produced by turbulence, inheriting its scale‐invariance and compressibility. The estimated asymmetry in plasma beta between the CS boundaries is shown to be insufficient to suppress magnetic reconnection through the diamagnetic drift of X‐line. The presented results will be of value for future comparative analysis of CSs observed at different distances from the Sun.

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Section: Introductionmentioning

confidence: 73%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

Vasko,

Alimov,

Phan

et al. 2024

JGR Space Physics

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Directional discontinuities in the inner heliosphere from Parker Solar Probe and Solar Orbiter observations

Madar,

Opitz,

Erdos

et al. 2024

A&A

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Context. Directional discontinuities (DDs) are common structures in the solar wind plasma and are among the most important discontinuities besides shock waves. The Parker Solar Probe and Solar Orbiter spacecraft currently provide whole new insight into the inner heliosphere in spatial coverage and timescales. Aims. We search for DDs and classify them into subgroups of tangential (TD) and rotational (RD) discontinuities. The analysis of the DD thicknesses allows us to test different theories about their origin and evolution. Methods. We applied an automatic algorithm to select discontinuities between heliocentric distances of 0.06–1.01 AU. The method uses the spatial rotation of the magnetic field to identify the DDs and minimum variance analysis to determine the normal vector of the discontinuity surface. A classification into TDs and RDs was carried out using the magnetic field data and the Walén test in both the spacecraft and the deHoffmann–Teller frame. Results. With strict conditions, we found more than 140 000 DDs in the time intervals. We find that the spatial density of DDs decreases with increasing radial distance from the Sun in the innermost heliosphere. The comprehensive analysis revealed that most of the DD, for which the normal component of the magnetic field is small are in fact TDs, regardless of the jump in field magnitude. After the classification, we were able to determine the radial thickness evolution for the TDs and RDs separately. We found that the thickness of RDs decreases from 0.06 to 0.30 AU, and beyond this (0.30–1.01 AU) it increases with the local ion inertial length. This characteristic scaling is present for TDs throughout between 0.06 and 1.01 AU. Conclusions. Our results give us a simple classification tool for future studies of DDs, that is based only on magnetic field measurements. After we analyzed the DD thickness, we observationally confirmed that RDs are produced by Alfvén-wave steepening, while the TDs are most likely the boundaries of flux tubes.

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Embedded Coherent Structures from Magnetohydrodynamics to Sub-ion Scales in Turbulent Solar Wind at 0.17 au

Vinogradov,

Alexandrova,

Démoulin

et al. 2024

ApJ

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We study intermittent coherent structures in solar wind turbulence from MHD to kinetic plasma scales using Parker Solar Probe data during its first perihelion (at 0.17 au) in the highly Alfvénic slow solar wind. We detect coherent structures using Morlet wavelets. For the first time, we apply a multiscale analysis in physical space. At MHD scales within the inertial range, times scales τ ∈ (1, 102) s, we find (i) current sheets including switchback boundaries and (ii) Alfvén vortices. Within these events are embedded structures at smaller scales: typically Alfvén vortices at ion scales, τ ∈ (0.08, 1) s, and compressible vortices at sub-ion scales, τ ∈ 8(10−3, 10−2) s. The number of coherent structures grows toward smaller scales: we observe ∼200 events during a 5 hr time interval at MHD scales, ∼103 at ion scales, and ∼104 at sub-ion scales. In general, there are multiple structures of ion and sub-ion scales embedded within one MHD structure. There are also examples of ion and sub-ion scale structures outside MHD structures. To quantify the relative importance of different types of structures, we do a statistical comparison of the observed structures with the expectations of models of the current sheets and vortices. The results show the dominance of Alfvén vortices at all scales in contrast to the widespread view of the dominance of current sheets. This means that Alfvén vortices are important building blocks of Alfvénic solar wind turbulence.

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Solar Wind Current Sheets: MVA Inaccuracy and Recommended Single‐Spacecraft Methodology

Cited by 4 publications

References 123 publications

Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

Directional discontinuities in the inner heliosphere from Parker Solar Probe and Solar Orbiter observations

Embedded Coherent Structures from Magnetohydrodynamics to Sub-ion Scales in Turbulent Solar Wind at 0.17 au

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