A Tractable Estimate for the Dissipation Range Onset Wavenumber Throughout the Heliosphere

Engelbrecht, N. Eugene; Strauss, R. D.

doi:10.3847/1538-4357/aab495

Cited by 22 publications

(24 citation statements)

References 88 publications

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“…It is established that the dissipation of turbulence energy heats the solar wind protons and electrons simultaneously. However, it is not only the turbulence energy but also Coulomb collisions between solar wind protons and electrons, and the electron heat flux that influence the heating profile of the solar wind protons and electrons (Cranmer et al 2009;Breech et al 2009;Engelbrecht & Strauss 2018;Chhiber et al 2019;Adhikari et al 2021…”

Section: Solar Wind Plus Ni Mhd Turbulence Transport Modelmentioning

confidence: 99%

“…However, the electron heat flux and the turbulence heating influence the solar wind electron temperature, and the turbulence heating alone affects the solar wind proton temperature. In this study, we assume that sixty percent of the available turbulent energy heats the solar wind protons, and forty percent the solar wind electrons (Breech et al 2009;Engelbrecht & Strauss 2018;Adhikari et al 2021). In the fast solar wind, the theoretical proton temperature decreases as r −1.26 , which is more rapidly than the radial profile of the slow solar wind temperature.…”

Section: Radial Evolution Of Solar Wind Background Profilementioning

confidence: 99%

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

Adhikari

Zank

Zhao

et al. 2021

A&A

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Aims. Solar Orbiter (SolO) was launched on February 9, 2020, allowing us to study the nature of turbulence in the inner heliopshere. We investigate the evolution of anisotropic turbulence in the fast and slow solar wind in the inner heliosphere using the nearly incompressible magnetohydrodynamic (NI MHD) turbulence model and SolO measurements. Methods. We calculated the two dimensional (2D) and the slab variances of the energy in forward and backward propagating modes, the fluctuating magnetic energy, the fluctuating kinetic energy, the normalized residual energy, and the normalized cross-helicity as a function of the angle between the mean solar wind speed and the mean magnetic field (θ U B ), and as a function of the heliocentric distance using SolO measurements. We compared the observed results and the theoretical results of the NI MHD turbulence model as a function of the heliocentric distance. Results. The results show that the ratio of 2D energy and slab energy of forward and backward propagating modes, magnetic field fluctuations, and kinetic energy fluctuations increases as the angle between the mean solar wind flow and the mean magnetic field increases from θ U B = 0 • to approximately θ U B = 90 • and then decreases as θ U B → 180 • . We find that solar wind turbulence is a superposition of the dominant 2D component and a minority slab component as a function of the heliocentric distance. We find excellent agreement between the theoretical results and observed results as a function of the heliocentric distance.

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Section: Solar Wind Plus Ni Mhd Turbulence Transport Modelmentioning

confidence: 99%

Section: Radial Evolution Of Solar Wind Background Profilementioning

confidence: 99%

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

Adhikari

Zank

Zhao

et al. 2021

A&A

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“…The study by Leamon et al [100] found that about 60% of the turbulent energy heats solar wind protons at 1 au. Using 60% of the turbulence energy to heat solar wind protons and 40% of the turbulence energy to heat solar wind electrons, Breech et al [11] developed a turbulence model that included electrons [11,47,93,[101][102][103]. They found that the solar wind proton and electron temperatures decrease slower than that expected of an adiabatic radial profile, viz.…”

Section: Incompressible Mhd Turbulence Model: Proton and Electron Heatingmentioning

confidence: 99%

“…We assume f p = 0.6 throughout the helioshere [11]. However, a few authors also assumed that f p = f p (r) [102,116,117]. The turbulent heating term S t can be derived from a von Kármán-Taylor phenomenology, and is given by [23,34],…”

Section: Incompressible Mhd Turbulence Model: Proton and Electron Heatingmentioning

confidence: 99%

The Transport and Evolution of MHD Turbulence throughout the Heliosphere: Models and Observations

Adhikari

Zank

Zhao

2021

Fluids

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A detailed study of solar wind turbulence throughout the heliosphere in both the upwind and downwind directions is presented. We use an incompressible magnetohydrodynamic (MHD) turbulence model that includes the effects of electrons, the separation of turbulence energy into proton and electron heating, the electron heat flux, and Coulomb collisions between protons and electrons. We derive expressions for the turbulence cascade rate corresponding to the energy in forward and backward propagating modes, the fluctuating kinetic and magnetic energy, the normalized cross-helicity, and the normalized residual energy, and calculate the turbulence cascade rate from 0.17 to 75 au in the upwind and downwind directions. Finally, we use the turbulence transport models to derive cosmic ray (CR) parallel and perpendicular mean free paths (mfps) in the upwind and downwind heliocentric directions. We find that turbulence in the upwind and downwind directions is different, in part because of the asymmetric distribution of new born pickup ions in the two directions, which results in the CR mfps being different in the two directions. This is important for models that describe the modulation of cosmic rays by the solar wind.

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“…To model k d , the bestfit proton gyrofrequency model from Leamon et al (2000) is employed, following the approach of Engelbrecht & Burger (2010) and Engelbrecht & Burger (2013b). The effects of using the more self-consistent approach to modeling this quantity proposed by Engelbrecht & Strauss (2018) will be the subject of future study. Furthermore, note that R=R L k min , the R L the maximal particle Larmor radius, and that B o and B slab 2 d , respectively, denote the HMF magnitude and slab variance.…”

Section: The Effects Of the 2d Outerscale On Galactic Cr Electron Modmentioning

confidence: 99%

The Implications of Simple Estimates of the 2D Outerscale Based on Measurements of Magnetic Islands for the Modulation of Galactic Cosmic-Ray Electrons

Engelbrecht

2019

ApJ

Self Cite

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The behavior of the 2D turbulence power spectrum at the lowest wavenumbers has a significant effect on the perpendicular diffusion coefficients of charged particles in the heliosphere derived from various scattering theories, and subsequently used to model the transport of cosmic rays (CRs) and solar energetic particles. In this regard, the lengthscale at which the energy-containing range begins, as opposed to that at which the inertial range commences, is of particular interest. This 2D outerscale has, however, never before been directly observed. Recently, direct measurements of magnetic islands in the solar wind have been reported by various authors. Assuming that these may provide an estimate of the 2D ultrascale, the direct calculation of the 2D outerscale becomes possible, should an observationally motivated form for the 2D turbulence power spectrum be employed. This study presents the results of such a calculation and provides comparisons of these with previous estimates of the 2D outerscale. Furthermore, the sensitivity of galactic CR electron intensities, calculated using a 3D ab initio CR modulation model, is demonstrated, and conclusions are drawn therefrom.

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A Tractable Estimate for the Dissipation Range Onset Wavenumber Throughout the Heliosphere

Cited by 22 publications

References 88 publications

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

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

The Transport and Evolution of MHD Turbulence throughout the Heliosphere: Models and Observations

The Implications of Simple Estimates of the 2D Outerscale Based on Measurements of Magnetic Islands for the Modulation of Galactic Cosmic-Ray Electrons

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