Simple Analytical Forms of the Perpendicular Diffusion Coefficient for Two-component Turbulence. III. Damping Model of Dynamical Turbulence

Gammon, Michael; Shalchi, A.

doi:10.3847/1538-4357/aa8950

Cited by 12 publications

(4 citation statements)

References 48 publications

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“…Perpendicular mean free path expressions from theory, however, can behave in a manner quite different from what is assumed in this study (see, e.g. Shalchi 2009;Engelbrecht & Burger 2015;Gammon & Shalchi 2017). For a preliminary study, however, the above expression for κ ⊥ should provide a reasonable approximation that meets the requirements for the scientific tasks investigated herein.…”

Section: Calculating Differential Intensitiesmentioning

confidence: 67%

The residence-time of Jovian electrons in the inner heliosphere

Vogt

Engelbrecht

Strauss

et al. 2020

A&A

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Context. Jovian electrons serve an important role in test-particle distribution in the inner heliosphere. They have been used extensively in the past to study the (diffusive) transport of cosmic rays in the inner heliosphere. With new limits on the Jovian source function, that is, the particle intensity just outside the Jovian magnetosphere, and a new set of in-situ observations at 1 AU for cases of both good and poor magnetic connection between the source and observer, we revisit some of these earlier simulations. Aims. We aim to find the optimal numerical set-up that can be used to simulate the propagation of 6 MeV Jovian electrons in the inner heliosphere. Using such a setup, we further aim to study the residence (propagation) times of these particles for different levels of magnetic connection between Jupiter and an observer at Earth (1 AU). Methods. Using an advanced Jovian electron propagation model based on the stochastic differential equation approach, we calculated the Jovian electron intensity for different model parameters. A comparison with observations leads to an optimal numerical setup, which was then used to calculate the so-called residence (propagation) times of these particles. Results. Through a comparison with in-situ observations, we were able to derive transport parameters that are appropriate for the study of the propagation of 6 MeV Jovian electrons in the inner heliosphere. Moreover, using these values, we show that the method of calculating the residence time applied in the existing literature is not suited to being interpreted as the propagation time of physical particles. This is due to an incorrect weighting of the probability distribution. We applied a new method, where the results from each pseudo-particle are weighted by its resulting phase-space density (i.e. the number of physical particles that it represents). We thereby obtained more reliable estimates for the propagation time.

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Section: Calculating Differential Intensitiesmentioning

confidence: 67%

The residence-time of Jovian electrons in the inner heliosphere

Vogt

Engelbrecht

Strauss

et al. 2020

A&A

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show abstract

“…Although the above expressions represent an essentially ad hoc approach to modelling diffusion parameters, the radial dependencyof the parallel diffusion coefficient does reproduce the corresponding behaviour of the quasi-linear theory electron parallel diffusion coefficient employed by Engelbrecht & Burger (2013), between 1 and 5 AU. Perpendicular mean free path expressions from theory, however, can behave in a manner quite different from what is assumed in this study (see, e.g., Shalchi 2009;Engelbrecht & Burger 2015;Gammon & Shalchi 2017). For a preliminary study, however, the above expression for κ ⊥ should provide a reasonable approximation that meets the requirements for the scientific tasks investigated herein.…”

Section: Calculating Differential Intensitiesmentioning

confidence: 67%

Jovian electrons in the inner heliosphere

Vogt

Heber

Kopp

et al. 2018

A&A

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Context. Jovian electrons serve as an important test-particle distribution in the inner heliosphere and have been used extensively in the past to study the (diffusive) transport of cosmic rays in the inner heliosphere. With new limits on the Jovian source function (i.e. the particle intensity just outside the Jovian magnetosphere), and a new set of in-situ observations at 1 AU for both cases of good and poor magnetic connection between the source and observer, we revisit some of these earlier simulations. Aims. We aim to find the optimal numerical set-up that can be used to simulate the propagation of 6 MeV Jovian electrons in the inner heliosphere. Using such a set-up, we further aim to study the residence (propagation) times of these particles for different levels of magnetic connection between Jupiter and an observer at Earth (1 AU). Methods. Using an advanced Jovian electron propagation model based on the stochastic differential equation (SDE) approach, we calculate the Jovian electron intensity for different model parameters. A comparison with observations leads to an optimal numerical set-up, which is then used to calculate the so-called residence (propagation) times of these particles.Results. Comparing to in-situ observations, we are able to derive transport parameters that are appropriate to study the propagation of 6 MeV Jovian electrons in the inner heliosphere. Moreover, using these values, we show that the method of calculating the residence time applied in former literature is not suited to being interpreted as the propagation time of physical particles. This is due to an incorrect weighting of the probability distribution. We propose and apply a new method, where the results from each pseudo-particle are weighted by its resulting phase-space density (i.e. the number of physical particles that it represents). Thereby we obtain more reliable estimates for the propagation time.

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“…with γ as a dynamical decay rate (see Bieber et al 1994;Gammon & Shalchi 2017) and, with the backtracking correction proposed by Ruffolo et al (2012),…”

Section: Perpendicular Diffusionmentioning

confidence: 99%

“…In what follows, the dynamical decay rate is set to zero (the magnetostatic case). This is a reasonable assumption, unless low-energy electrons are considered (for more details, see Engelbrecht & Burger 2013b;Gammon & Shalchi 2017;Strauss & le Roux 2019).…”

Section: Perpendicular Diffusion Coefficients Comparedmentioning

confidence: 99%

On the Pitch-angle-dependent Perpendicular Diffusion Coefficients of Solar Energetic Protons in the Inner Heliosphere

Engelbrecht

2019

ApJ

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Various numerical solar energetic particle (SEP) transport studies have shown that perpendicular diffusion plays a significant role in the propagation of these particles in the heliosphere. In particular, computed SEP intensities and anisotropies have been shown to be sensitive to the pitch-angle dependence of the perpendicular diffusion coefficient as well as its magnitude. This study proposes a novel approach to the calculation of this quantity and compares this to the results of previous theoretical approaches. These various perpendicular diffusion coefficient expressions are demonstrated for turbulence conditions prevalent at Earth and closer to the Sun.

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Simple Analytical Forms of the Perpendicular Diffusion Coefficient for Two-component Turbulence. III. Damping Model of Dynamical Turbulence

Cited by 12 publications

References 48 publications

The residence-time of Jovian electrons in the inner heliosphere

The residence-time of Jovian electrons in the inner heliosphere

Jovian electrons in the inner heliosphere

On the Pitch-angle-dependent Perpendicular Diffusion Coefficients of Solar Energetic Protons in the Inner Heliosphere

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