Average properties of cosmic ray diffusion in solar wind streams

Morfill, G. E.; Richter, A. K.; Scholer, M.

doi:10.1029/ja084ia04p01505

Cited by 37 publications

(24 citation statements)

References 24 publications

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“…(if the assumption of a steady state is not made, the intensity of accelerated particles depends on the diffusion coefficient. Recent calculations based on observed solar wind and magnetic field parameters [Morrill et al, 1979] show that the diffusion coefficient should be longitude independent for the regions of interest here. Thus if the forward and reverse shocks were formed at the same time, again no systematic difference in accelerated particle intensity should be observed, unless either the source population or the shock acceleration strength is different.…”

Section: Asymmetries In Corotating Eventsmentioning

confidence: 84%

On the origin of corotating energetic particle events

Scholer¹,

Morfill²,

Hollebeke³

1980

J. Geophys. Res.

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Energetic corotating particle events could be produced by acceleration at the forward and reverse shock pair, which bounds a corotating interaction region, via the process of successive multiple reflections. In the steady state, which should be the situation applicable to corotating events, the energetic particle intensity at the shock depends only on the acceleration strength of the shock and on the intensity of the source particles. Measurements of energetic particles show systematic variations: intensities at the forward shock are typically smaller than those at the reverse shock and increase with heliocentric distance (between ∼1 and 5 AU), whereas intensities at the reverse shock tend to decrease with heliocentric distance. Since there is no obvious difference between forward and reverse shock strengths, the origin for this behavior could lie in the particle source. Assuming that this source is part of the solar wind plasma and that the solar wind temperature is the best available indicator for the intensity of these particles, it is argued that a correlation between energetic particle intensities and plasma temperature should exist. Detailed analysis of individual events, as well as a statistical analysis, yields such a correlation. This suggests that the solar wind is the original particle population that is accelerated in the stationary shocks up to several MeV.

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Section: Asymmetries In Corotating Eventsmentioning

confidence: 84%

On the origin of corotating energetic particle events

Scholer¹,

Morfill²,

Hollebeke³

1980

J. Geophys. Res.

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“…More recently, a special model of a Forbush decrease based on convective-diffusive transport and a linear sink of particles propagating through the solar wind was suggested by Bland [1976]. Morrill et al [1979] computed the spatial diffusion coefficient expected in a fast and in a slow stream and in the intervening corotating interaction region and derived corotating 27-day variation profiles based on the azimuthal variation of the diffusion coefficient in essential agreement with neutron monitor observations. Gall [1982, 1984] have performed Monte Carlo calculations of particle transport in the enhanced magnetic fields associated with corotating interaction regions and propagating interplanetary shocks.…”

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confidence: 81%

A perturbation approach to cosmic ray transients in interplanetary space

Chih

Lee

1986

J. Geophys. Res.

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A general linear response analysis is presented for investigating cosmic ray transients in interplanetary space. The diffusion equation for energetic particle transport in the solar wind is first linearized about a stationary configuration. The perturbation in the particle omnidirectional distribution function resulting from perturbations to the solar wind velocity, drift velocity, or spatial diffusion tensor corresponding to transient solar wind conditions may then be found by solving an inhomogeneous boundary value problem. As illustrative examples of the general analysis, transient perturbations in the cosmic ray number density due to variations in the spatial diffusion coefficient are computed in a one‐dimensional solar wind based on the convection‐diffusion equation, which disregards cosmic ray energy changes in the solar wind. Two variations are considered, corresponding to (1) a Forbush decrease arising from the passage of an interplanetary traveling disturbance (shock) and (2) the solar cycle variation arising from an 11‐year sinusoidal variation of the spatial diffusion coefficient at the sun which then propagates out through the heliosphere. The predicted solar cycle variation exhibits a hysteresis effect in which high‐energy particles lead low‐energy particles and a time delay which increases with heliocentric distance within the inner heliosphere. The predicted Forbush decrease profiles exhibit precursors, precipitous decreases, and gradual approximately energy‐independent recoveries arising from a decay of the propagating disturbance. The general features of both variations are in accord with observations.

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“…The latter coincided with the moments which are likely to be a kind of a channel for SCR propagation. An analysis of the power density spectra of the IMF fluctuations also indicates the existence of channels in the interplanetary medium that provide for anisotropic "conductivity" for the cosmic ray "current" (e.g., Morfill et al 1979). used numerical solution of the kinetic equation in the drift approximation (Toptygin 1985) for appropriate boundary conditions in order to describe the propagation of SCR in the presence of loops and magnetic mirrors.…”

Section: Particle Motion In the Large-scale Magnetic Structuresmentioning

confidence: 99%

Solar Cosmic Rays

Miroshnichenko

2015

Astrophysics and Space Science Library

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Average properties of cosmic ray diffusion in solar wind streams

Cited by 37 publications

References 24 publications

On the origin of corotating energetic particle events

On the origin of corotating energetic particle events

A perturbation approach to cosmic ray transients in interplanetary space

Solar Cosmic Rays

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