Large Amplitude Switchback Turbulence: Possible Magnetic Velocity Alignment Structures

Wu, Hongjie; Tu, Chuanyi; Wang, Xin; Yang, Liping

doi:10.3847/1538-4357/abec6c

Cited by 13 publications

(7 citation statements)

References 31 publications

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“…The analysis also shows that the turbulence is found to be less imbalanced with higher residual energy in switchback intervals. Wu et al (2021) has investigated the turbulent quantities such as the normalized cross helicity and the residual energy in switchbacks using the first four Encs. of PSP data.…”

Section: Turbulence Characteristics Within Switchbacksmentioning

confidence: 99%

Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

et al. 2023

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Launched on 12 Aug. 2018, NASA’s Parker Solar Probe had completed 13 of its scheduled 24 orbits around the Sun by Nov. 2022. The mission’s primary science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Parker Solar Probe returned a treasure trove of science data that far exceeded quality, significance, and quantity expectations, leading to a significant number of discoveries reported in nearly 700 peer-reviewed publications. The first four years of the 7-year primary mission duration have been mostly during solar minimum conditions with few major solar events. Starting with orbit 8 (i.e., 28 Apr. 2021), Parker flew through the magnetically dominated corona, i.e., sub-Alfvénic solar wind, which is one of the mission’s primary objectives. In this paper, we present an overview of the scientific advances made mainly during the first four years of the Parker Solar Probe mission, which go well beyond the three science objectives that are: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles.

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Section: Turbulence Characteristics Within Switchbacksmentioning

confidence: 99%

Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

et al. 2023

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“…Indeed, switchbacks are usually identified as a deflection from a background magnetic field, and it is obvious that the choice of this background field directly affects the results one would obtain regarding their orientation. In the literature, various background definitions have been used to identify switchbacks in statistical studies, for instance: the radial direction (Woolley et al 2020;Wu et al 2021;Bourouaine et al 2020;Mozer et al 2020), a 6h median field (Dudok de Wit et al 2020), a 6h mean field (Bandyopadhyay et al 2021), a 1h mode field (Bale et al 2019), and a modeled Parker spiral field (Horbury et al 2020;Laker et al 2021;Fargette et al 2021). Various threshold were used, from 30 to 90 • , as well as additional selection criteria such as duration, field magnitude, Alfvénicity, and density, which are not discussed here.…”

Section: Switchback Definitionmentioning

confidence: 99%

The preferential orientation of magnetic switchbacks and its implications for solar magnetic flux transport

Fargette

Lavraud

Rouillard

et al. 2022

A&A

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Context. Magnetic switchbacks in the solar wind are large deflections of the magnetic field vector, which often reverse their radial component, and are associated with a velocity spike consistent with their Alfvénic nature. The Parker Solar Probe (PSP) mission revealed them to be a dominant feature of the near-Sun solar wind. Where and how they are formed remains unclear and subject to discussion. Aims. We investigate the orientation of the magnetic field deflections in switchbacks to determine if they are characterized by a possible preferential orientation. Methods. We compute the deflection angles, ψ = [ϕ, θ]T, of the magnetic field relative to the theoretical Parker spiral direction for encounters 1 to 9 of the PSP mission. We first characterize the distribution of these deflection angles for quiet solar wind intervals and assess the precision of the Parker model as a function of distance from the Sun. We then assume that the solar wind is composed of two populations, the background quiet solar wind and the population of switchbacks, the latter of which is characterized by larger fluctuations. We model the total distribution of deflection angles we observe in the solar wind as a weighed sum of two distinct normal distributions, each corresponding to one of the populations. We fit the observed data with our model using a Monte Carlo Markov chain algorithm and retrieve the most probable mean vector and covariance matrix coefficients of the two Gaussian functions, as well as the population proportion. This method allows us to quantify the properties of both the quiet solar wind and the switchback populations without setting an arbitrary threshold on the magnetic field deflection angles. Results. We first confirm that the Parker spiral is a valid model for quiet solar wind intervals at PSP distances. We observe that the accuracy of the spiral direction in the ecliptic is a function of radial distance, in a manner that is consistent with PSP being near the solar wind acceleration region. We then find that the fitted switchback population presents a systematic bias in its deflections, with a mean vector consistently shifted toward lower values of ϕ (−5.52° on average) and θ (−2.15° on average) compared to the quiet solar wind population. This results holds for all encounters but encounter 6, and regardless of the magnetic field main polarity. This implies a marked preferential orientation of switchbacks in the clockwise direction in the ecliptic plane, and we discuss this result and its implications in the context of the existing switchback formation theories. Finally, we report the observation of a 12-hour patch of switchbacks that systematically deflect in the same direction, such that the magnetic field vector tip within the patch deflects and returns to the Parker spiral within a given plane.

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“…Moreover, turbulence may also work to generate switchbacks as suggested by several works (e.g., Bourouaine et al 2020;Shoda et al 2021;Wu et al 2021;Pecora et al 2022), but it may not be the primary formation mechanism based on our results. PVI values also measure the intermittency in turbulence, thus large PVI values indicate strong intermittency in the turbulence.…”

Section: The Origins Of Switchbacksmentioning

confidence: 56%

The Structure and Origin of Switchbacks: Parker Solar Probe Observations

Huang

Kasper

Fisk

et al. 2023

ApJ

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Switchbacks are rapid magnetic field reversals that last from seconds to hours. Current Parker Solar Probe (PSP) observations pose many open questions in regard to the nature of switchbacks. For example, are they stable as they propagate through the inner heliosphere, and how are they formed? In this work, we aim to investigate the structure and origin of switchbacks. In order to study the stability of switchbacks, we suppose the small-scale current sheets therein are generated by magnetic braiding, and they should work to stabilize the switchbacks. With more than 1000 switchbacks identified with PSP observations in seven encounters, we find many more current sheets inside than outside switchbacks, indicating that these microstructures should work to stabilize the S-shape structures of switchbacks. Additionally, we study the helium variations to trace the switchbacks to their origins. We find both helium-rich and helium-poor populations in switchbacks, implying that the switchbacks could originate from both closed and open magnetic field regions in the Sun. Moreover, we observe that the alpha-proton differential speeds also show complex variations as compared to the local Alfvén speed. The joint distributions of both parameters show that low helium abundance together with low differential speed is the dominant state in switchbacks. The presence of small-scale current sheets in switchbacks along with the helium features are in line with the hypothesis that switchbacks could originate from the Sun via interchange reconnection process. However, other formation mechanisms are not excluded.

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Large Amplitude Switchback Turbulence: Possible Magnetic Velocity Alignment Structures

Cited by 13 publications

References 31 publications

Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

Parker Solar Probe: Four Years of Discoveries at Solar Cycle Minimum

The preferential orientation of magnetic switchbacks and its implications for solar magnetic flux transport

The Structure and Origin of Switchbacks: Parker Solar Probe Observations

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