Evolution of anisotropic turbulence in the fast and slow solar wind: Theory and Solar Orbiter measurements

Adhikari, L.; Zank, G. P.; Zhao, Lingling; Telloni, Daniele; Horbury, T. S.; O’Brien, H.; Evans, V.; Angelini, V.; Owen, C. J.; Fedorov, A.

doi:10.1051/0004-6361/202140672

Cited by 19 publications

(22 citation statements)

References 75 publications

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“…Using Equations (10) and (11) we calculate the transverse magnetic field fluctuations in a plane perpendicular to the mean magnetic field. To calculate the transverse Elsässer energies and fluctuating kinetic energy, the variance matrix S ij is formed by the R, T, and N components of the Elsässer variables and the fluctuating solar wind speed, respectively (Adhikari et al 2021c). Then, we calculate the observed 2D and slab turbulence energies based on two criteria discussed above.…”

Section: Methodsmentioning

confidence: 99%

“…The first, second, and third terms on the right-hand side (rhs) of Equations ( 14) and (15) yield the R, T, and N components of the perpendicular and parallel fluctuating magnetic field and solar wind speed. Using the R, T, and N components of the perpendicular fluctuating fields, we calculate the transverse turbulence energy and correlation length by following the same approach as in our previous papers (Zank et al 1996;Adhikari et al 2014Adhikari et al , 2015Adhikari et al , 2017aShiota et al 2017;Zhao et al 2018;Adhikari et al 2021c). We then calculate the observed 2D and slab turbulence components from the transverse values using the criteria based on θ UB values.…”

Section: Methodsmentioning

confidence: 99%

“…For the slow solar wind of PSP, we use the data sets at times (DOY:HR: MIN): 309:3:18−311:12:44, 313:9:29−314:3:20, 315:16:52 −317:22:59, 324:22:51−325:13:19, and 332:7:52−333:23:57 of the year 2018 (see Adhikari et al 2020a). Similarly, for the slow solar wind of SolO, we use the data sets at times (YY:MN: DD): 2020-07-17, 2020-07-18, 2020-07-22, 2020-07-30, 2020-08-02, 2020-08-03, 2020-08-04, 2020-08-05, 2020-08-07, 2020-08-08, 2020-08-09, 2020-08-11, and 2020-08-13 (see Adhikari et al 2021c). During the period of our study, PSP and SolO stay within a latitude of 5°.…”

Section: Radial Evolution Of 2d and Slab Turbulencementioning

confidence: 99%

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MHD Turbulent Power Anisotropy in the Inner Heliosphere

Adhikari¹,

Zank²,

Zhao³

et al. 2022

ApJ

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We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ UB of either (i) 65° < θ UB < 115° or (ii) 0° < θ UB < 25° (155° < θ UB < 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Radial Evolution Of 2d and Slab Turbulencementioning

confidence: 99%

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MHD Turbulent Power Anisotropy in the Inner Heliosphere

Adhikari¹,

Zank²,

Zhao³

et al. 2022

ApJ

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“…This has been noted (Chhiber et al 2021b;Zank et al 2021) as a likely reason that PSP correlation scales near perihelion are systematically smaller than might be expected based on extrapolation from 1 au observations and general trends from Helios observations. A recent turbulence transport calculation based on a "slab" (parallel) and "2D" (perpendicular) representation of turbulence is able to reproduce the correlation scales found in selected parallel intervals in PSP data near perihelion (Adhikari et al 2021) with appropriate choice of parameters. This model result does not address the underlying question as to what is the physical cause of the smaller parallel correlation lengths nor the values of perpendicular scales (which are not observed).…”

Section: Discussionmentioning

confidence: 99%

Intermittency in the Expanding Solar Wind: Observations from Parker Solar Probe (0.16au), Helios 1 (0.3-1au), and Voyager 1 (1-10au)

Cuesta,

Parashar,

Chhiber

et al. 2022

Preprint

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We examine statistics of magnetic field vector components to explore how intermittency evolves from near Sun plasma to radial distances as large as 10 au. Statistics entering the analysis include auto-correlation, magnetic structure functions of order n (SF n ), and scale dependent kurtosis (SDK), each grouped in ranges of heliocentric distance. The Goddard Space Flight Center Space Physics Data Facility (SPDF) provides magnetic field measurements for resolutions of 6.8 ms for Parker Solar Probe, 6 s for Helios, and 1.92 s for Voyager 1. We compute SF 2 to determine the scales encompassing the inertial range and examine SDK to investigate degree of non-Gaussianity. Auto-correlations are used to resolve correlation scales. Correlation lengths and ion inertial lengths provide an estimate of effective Reynolds number (R e ). Variation in R e allows us to examine for the first time the relationship between SDK and R e in an interplanetary plasma. A conclusion from this observed relationship is that regions with lower R e at a fixed physical scale have on average lower kurtosis, implying less intermittent behavior. Kolmogorov refined similarity hypothesis is applied to magnetic SF n and kurtosis to calculate intermittency parameters and fractal scaling in the inertial range. A refined Voyager 1 magnetic field dataset is generated.

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“…The evolution of the outward wave dominance as well as the evolution of the spectral break point with distance is supported by MHD simulations of turbulence (Roberts et al, 1991). As physicsbased models of turbulence become more complex, they are able to reproduce many of the observed characteristics of the solar wind (Roberts and Ofman, 2019;Adhikari et al, 2021).…”

Section: Turbulent Structuring In the Solar Windmentioning

confidence: 91%

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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Evolution of anisotropic turbulence in the fast and slow solar wind: Theory and Solar Orbiter measurements

Cited by 19 publications

References 75 publications

MHD Turbulent Power Anisotropy in the Inner Heliosphere

MHD Turbulent Power Anisotropy in the Inner Heliosphere

Intermittency in the Expanding Solar Wind: Observations from Parker Solar Probe (0.16au), Helios 1 (0.3-1au), and Voyager 1 (1-10au)

Mesoscale Structure in the Solar Wind

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