Multiscale Solar Wind Turbulence Properties inside and near Switchbacks Measured by the Parker Solar Probe

Martinović, M.; Klein, K. G.; Huang, Jia; Chandran, Benjamin D. G.; Kasper, J. C.; Lichko, Emily; Bowen, T. A.; Chen, Christopher H. K.; Matteini, Lorenzo; Stevens, Michael L.; Case, A. W.; Bale, S. D.

doi:10.3847/1538-4357/abebe5

Cited by 30 publications

(48 citation statements)

References 114 publications

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“…Entropy also increases and has less variability with distance, indicating heating and turbulent processing (Roberts et al, 2005). The so-called switchbacks observed by Parker Solar Probe exhibit different break scales between inertial and dissipation scales and increased level of intermittency than the surrounding wind, perhaps contributing to the turbulent heating in the inner heliosphere (Martinović et al, 2021).…”

Section: Turbulent Structuring In the Solar Windmentioning

confidence: 98%

“…Switchbacks are another example of mesoscale structures that could be remnants of reconnection at the Sun, or shear flows from structure at the Sun, or turbulence. (Martinović et al, 2021) presented evidence of their formation via turbulence, while (Larosa et al, 2021) argue for the firehose instability to play a role, since only 73% of switchbacks are Alfvénic. (Drake et al, 2021) argue that switchbacks are the result of flux ropes created through interchange reconnection in the corona, and (Tenerani et al, 2020) modeled switchbacks and showed that they persist for up to hundreds of Alfvén crossing times, and thus could be formed in the corona.…”

Section: Differentiating Injected/imposed Vs Turbulent Structurementioning

confidence: 99%

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Mesoscale Structure in the Solar Wind

Viall

DeForest

Kepko

2021

Front. Astron. Space Sci.

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Structures in the solar wind result from two basic mechanisms: structures injected or imposed directly by the Sun, and structures formed through processing en route as the solar wind advects outward and fills the heliosphere. On the largest scales, solar structures directly impose heliospheric structures, such as coronal holes imposing high speed streams of solar wind. Transient solar processes can inject large-scale structure directly into the heliosphere as well, such as coronal mass ejections. At the smallest, kinetic scales, the solar wind plasma continually evolves, converting energy into heat, and all structure at these scales is formed en route. “Mesoscale” structures, with scales at 1 AU in the approximate spatial range of 5–10,000 Mm and temporal range of 10 s–7 h, lie in the orders of magnitude gap between the two size-scale extremes. Structures of this size regime are created through both mechanisms. Competition between the imposed and injected structures with turbulent and other evolution leads to complex structuring and dynamics. The goal is to understand this interplay and to determine which type of mesoscale structures dominate the solar wind under which conditions. However, the mesoscale regime is also the region of observation space that is grossly under-sampled. The sparse in situ measurements that currently exist are only able to measure individual instances of discrete structures, and are not capable of following their evolution or spatial extent. Remote imaging has captured global and large scale features and their evolution, but does not yet have the sensitivity to measure most mesoscale structures and their evolution. Similarly, simulations cannot model the global system while simultaneously resolving kinetic effects. It is important to understand the source and evolution of solar wind mesoscale structures because they contain information on how the Sun forms the solar wind, and constrains the physics of turbulent processes. Mesoscale structures also comprise the ground state of space weather, continually buffeting planetary magnetospheres. In this paper we describe the current understanding of the formation and evolution mechanisms of mesoscale structures in the solar wind, their characteristics, implications, and future steps for research progress on this topic.

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Section: Turbulent Structuring In the Solar Windmentioning

confidence: 98%

Section: Differentiating Injected/imposed Vs Turbulent Structurementioning

confidence: 99%

Mesoscale Structure in the Solar Wind

Viall

DeForest

Kepko

2021

Front. Astron. Space Sci.

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“…More recent studies (Liang et al 2021;Martinović et al 2021;Dudok de Wit et al 2020) also report surveys, and vary rather significantly in both methodology and criteria for selecting events. To date, the origin of switchbacks remains a matter of debate.…”

Section: Radial Occurrence Of Switchbacksmentioning

confidence: 99%

Magnetic Switchback Occurrence Rates in the Inner Heliosphere: Parker Solar Probe and 1 au

Pecora,

Matthaeus,

Primavera

et al. 2022

Preprint

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The subject of switchbacks, defined either as large angular deflections or polarity reversals of the magnetic field, has generated substantial interest in the space physics community since the launch of Parker Solar Probe (PSP) in 2018. Previous studies have characterized switchbacks in several different ways, and have been restricted to data available from the first few orbits. Here, we analyze the frequency of occurrence of switchbacks per unit distance for the first full eight orbits of PSP. In this work, are considered switchback only the events that reverse the sign of magnetic field relative to a regional average. A significant finding is that the rate of occurrence falls off sharply approaching the sun near 0.2 au (40 R ), and rises gently from 0.2 au outward. The analysis is varied for different magnetic field cadences and for different local averages of the ambient field, confirming the robustness of the results. We discuss implications for the mechanisms of switchback generation. A publicly available database has been created with the identified reversals.

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“…-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) -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 o , as well as additional selection criteria such as duration, field magnitude, Alfvénicity, density, etc., that are not listed here. Visual selections of switchbacks were also performed often based on radial magnetic field reversals and their duration (Larosa et al 2021;Martinović et al 2021;Akhavan-Tafti et al 2021). Two kinds of approaches are typically used.…”

Section: Switchback Definitionmentioning

confidence: 99%

The preferential orientation of magnetic switchbacks, implications for solar magnetic flux transport

Fargette,

Lavraud,

Rouillard

et al. 2022

Preprint

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Context. Magnetic switchbacks in the solar wind are large deflections of the magnetic field vector, often reversing its radial component, and associated with a velocity spike consistent with their Alfvénic nature. The Parker Solar Probe (PSP) mission revealed that they were 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 characterised 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 calm 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 calm solar wind and the population of switchbacks, 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 population. 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.Results. We first confirm that the Parker spiral is a valid model for calm 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 towards lower values of φ (−5.52• on average) and θ (−2.15• on average) compared to the calm solar wind population. This results holds for all encounters but E6, 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, so that the magnetic field vector tip within the patch deflects and returns to the Parker spiral within a given plane.

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Multiscale Solar Wind Turbulence Properties inside and near Switchbacks Measured by the Parker Solar Probe

Cited by 30 publications

References 114 publications

Mesoscale Structure in the Solar Wind

Mesoscale Structure in the Solar Wind

Magnetic Switchback Occurrence Rates in the Inner Heliosphere: Parker Solar Probe and 1 au

The preferential orientation of magnetic switchbacks, implications for solar magnetic flux transport

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