On the Power-Law Distribution of Pitch-Angle Scattering Times in Solar Wind Turbulence

Perri, S.; Pucci, Francesco; Malara, F.; Zimbardo, G.

doi:10.1007/s11207-019-1421-y

Cited by 9 publications

(13 citation statements)

References 36 publications

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“…In fluid and plasma physics, the presence of turbulence-with its broad range of scales involved in the eddy size distribution-is one of the main factors causing anomalous transport [11,[15][16][17][18][19][20]. Further, in magnetized plasmas, an intriguing role that is yet to be fully understood is due to the scale-free distribution of pitch-angle scattering times [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

On the Fractional Diffusion-Advection Equation for Fluids and Plasmas

Zimbardo

Perri

2019

Fluids

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The problem of studying anomalous superdiffusive transport by means of fractional transport equations is considered. We concentrate on the case when an advection flow is present (since this corresponds to many actual plasma configurations), as well as on the case when a boundary is also present. We propose that the presence of a boundary can be taken into account by adopting the Caputo fractional derivatives for the side of the boundary (here, the left side), while the Riemann-Liouville derivative is used for the unbounded side (here, the right side). These derivatives are used to write the fractional diffusion–advection equation. We look for solutions in the steady-state case, as such solutions are of practical interest for comparison with observations both in laboratory and astrophysical plasmas. It is shown that the solutions in the completely asymmetric cases have the form of Mittag-Leffler functions in the case of the left fractional contribution, and the form of an exponential decay in the case of the right fractional contribution. Possible applications to space plasmas are discussed.

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Section: Introductionmentioning

confidence: 99%

On the Fractional Diffusion-Advection Equation for Fluids and Plasmas

Zimbardo

Perri

2019

Fluids

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“…The study allows the authors to investigate particle diffusion and acceleration phenomena. Perri et al (2019) study the dependence on the intermittency of the distribution of pitch-angle scattering tracking individual test particles in a turbulence spectrum comparable to that in the solar wind. Verdini, Grappin, and Montagud-Camps (2019) investigate the standard incompressible turbulent heating in the accelerating region, showing that the large-scale phenomenology is inaccurate and overestimates the heating by a factor Katushkina et al (2019) show that the WSA-Enlil model confirms qualitatively the latitudinal distribution of the solar wind found from the SWAN data.…”

Section: Topical Collection: Solar Wind At the Dawn Of The Parker Solmentioning

confidence: 99%

Editorial: Solar Wind at the Dawn of the Parker Solar Probe and Solar Orbiter Era

2020

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“…In other words, once the ratio c /ρ p is fixed, the particle scattering time predicted by the quasi-linear theory (QLT) should depend on the magnetic fluctuation amplitude relative to the background field. However, numerical simulations show that the distribution of the scattering time of energetic particles broadens around the quasi-linear approximation over about five orders of magnitude [33,34], suggesting a scale-free nature of the pitch angle scattering times. Such a broadening is augmented in the presence of δB/B 0 1 and high intermittency.…”

Section: Introductionmentioning

confidence: 97%

“…This problem has been extensively studied, showing that the presence of complex magnetic fields in molecular clouds leads to frequent cosmic rays' magnetic reflections that reduce cosmic ray diffusion within the Galactic disk. Recently, implementing a 3D isotropic model of static magnetic field turbulence [31] with adjustable turbulent spectral extension, fluctuation amplitude, and the degree of scale-dependent non Gaussianity, also called magnetic intermittency [32], the transport of energetic particles in the direction parallel and perpendicular to the mean field has been investigated [33,34]. Asymptotically, particles reach parallel and perpendicular diffusive regime (perpendicular subdiffusion is reached in case of very low magnetic field fluctuations).…”

Section: Introductionmentioning

confidence: 99%

“…This is in full agreement with the cosmic-ray diffusion studied in a test-particle simulation in 3D turbulence by [33] (see their Figure 5). Pucci et al [33] also found that intermittency has no particular influence on the transport of particles at different energies [34]. Although energetic particles perform parallel diffusion for long times, Pucci et al [33] found that the distribution of the particles' scattering times in pitch angle (computed by following the particles' trajectories and picking-up large pitch angle variations) does not peak at a the quasi-linear prediction:…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Magnetic Turbulence on the Energetic Particle Transport Upstream of Shock Waves

et al. 2021

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Energetic particles are ubiquitous in the interplanetary space and their transport properties are strongly influenced by the interaction with magnetic field fluctuations. Numerical experiments have shown that transport in both the parallel and perpendicular directions with respect to the background magnetic field is deeply affected by magnetic turbulence spectral properties. Recently, making use of a numerical model with three dimensional isotropic turbulence, the influence of turbulence intermittency and magnetic fluctuations on the energetic particle transport was investigated in the solar wind context. Stimulated by this previous theoretical work, here we analyze the parallel transport of supra-thermal particles upstream of interplanetary shock waves by using in situ particle flux measurements; the aim was to relate particle transport properties to the degree of intermittency of the magnetic field fluctuations and to their relative amplitude at the energetic particle resonant scale measured in the same regions. We selected five quasi-perpendicular and five quasi-parallel shock crossings by the ACE satellite. The analysis clearly shows a tendency to find parallel superdiffusive transport at quasi-perpendicular shocks, with a significantly higher level of the energetic particle fluxes than those observed in the quasi-parallel shocks. Furthermore, the occurrence of anomalous parallel transport is only weakly related to the presence of magnetic field intermittency.

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On the Power-Law Distribution of Pitch-Angle Scattering Times in Solar Wind Turbulence

Cited by 9 publications

References 36 publications

On the Fractional Diffusion-Advection Equation for Fluids and Plasmas

On the Fractional Diffusion-Advection Equation for Fluids and Plasmas

Editorial: Solar Wind at the Dawn of the Parker Solar Probe and Solar Orbiter Era

The Influence of Magnetic Turbulence on the Energetic Particle Transport Upstream of Shock Waves

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