Suppression of Particle Drifts by Turbulence

Minnie, J.; Bieber, J. W.; Matthaeus, W. H.; Burger, R. A.

doi:10.1086/522026

Cited by 98 publications

(105 citation statements)

References 27 publications

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“…In particular, the GG is well detected in CR intensity during the maximum phase of all solar cycles and delayed, with respect to SA, on average of about 6 months. The time lags observed near the sunspot maximum could be due to an efficient diffusion in such periods, when enhanced fluctuations in the magnetic field are expected, while the drift effects should be suppressed (e.g., Minnie et al 2007). The similarity between the CR and SA profiles confirms that the CR variability, at these timescales, is related to the ∼11 yr solar activity cycle (including QBOs), whose representative index is the SA.…”

Section: Solar Modulation Versus Drift Effectsmentioning

confidence: 99%

Drift Effects on the Galactic Cosmic Ray Modulation

Laurenza

Vecchio

Storini

et al. 2014

ApJ

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Cosmic ray (CR) modulation is driven by both solar activity and drift effects in the heliosphere, although their role is only qualitatively understood as it is difficult to connect the CR variations to their sources. In order to address this problem, the Empirical Mode Decomposition technique has been applied to the CR intensity, recorded by three neutron monitors at different rigidities (Climax, Rome, and Huancayo-Haleakala (HH)), the sunspot area, as a proxy for solar activity, the heliospheric magnetic field magnitude, directly related to CR propagation, and the tilt angle (TA) of the heliospheric current sheet (HCS), which characterizes drift effects on CRs. A prominent periodicity at ∼six years is detected in all the analyzed CR data sets and it is found to be highly correlated with changes in the HCS inclination at the same timescale. In addition, this variation is found to be responsible for the main features of the CR modulation during periods of low solar activity, such as the flat (peaked) maximum in even (odd) solar cycles. The contribution of the drift effects to the global Galactic CR modulation has been estimated to be between 30% and 35%, depending on the CR particle energy. Nevertheless, the importance of the drift contribution is generally reduced in periods nearing the sunspot maximum. Finally, threshold values of ∼40 • , ∼45 • , and >55 • have been derived for the TA, critical for the CR modulation at the Climax, Rome, and HH rigidity thresholds, respectively.

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Section: Solar Modulation Versus Drift Effectsmentioning

confidence: 99%

Drift Effects on the Galactic Cosmic Ray Modulation

Laurenza

Vecchio

Storini

et al. 2014

ApJ

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“…The functional form of u D is taken from Burger et al (2000), but assumed to be only 55% effective, based on A&A 522, A35 (2010) the modelling done by Potgieter (1989), Langner et al (2004) and Minnie et al (2007). Neutral sheet drift is due to the heliospheric current sheet (HCS) and as the modulation model is limited to solar minimum conditions, a HCS tilt angle of α = 10 • is assumed.…”

Section: The Modulation Modelmentioning

confidence: 99%

Modelling anomalous cosmic ray oxygen in the heliosheath

Strauss

Potgieter

Ferreira

et al. 2010

A&A

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This paper discusses a numerical modulation model to describe anomalous cosmic ray acceleration and transport in the heliosheath, the portion of the heliosphere between the termination shock and the heliopause. The model is based on the well known Parker transport equation and includes, in addition to diffusive shock acceleration at the solar wind termination shock, momentum diffusion (Fermi II, stochastic acceleration) and adiabatic heating occurring in the heliosheath together with both a latitude dependent compression ratio and injection efficiency as inferred from hydrodynamic heliospheric models. The model is applied to the study of anomalous cosmic ray oxygen, with the resulting intensities compared to recent Voyager 1 spacecraft observations in the heliosheath.Comparison shows that the model is able to very satisfactorily reproduce these observations, which includes a modulated spectral form at the termination shock and subsequent unfolding into the heliosheath. It is concluded that a combination of momentum diffusion and adiabatic heating, under certain realistic assumption of the solar wind speed in the heliosheath, form a viable re-acceleration mechanism, or continuous acceleration process, to explain the very contentious anomalous cosmic ray observations in the heliosheath.

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“…Although turbulence can suppress drifts (see Minnie et al 2007), we find a nonsymmetric behavior of particle scattering due to the assumption of nonaxisymmetric turbulence. For a flat spectrum in the energy range and for slab/2D composite geometry, we derived in particular…”

Section: Discussionmentioning

confidence: 81%

“…This motivates us to refer to these tensor elements as ''drift coefficients.'' Recently, however, Minnie et al (2007) have demonstrated, by use of a test particle code, that the drifts are usually suppressed when there is sufficiently strong turbulence. Thus, we believe that in such cases nonaxisymmetric particle scattering can be caused by nonaxisymmetric turbulence.…”

Section: Introductionmentioning

confidence: 99%

The Cosmic‐Ray Diffusion Tensor in Nonaxisymmetric Turbulence

Weinhorst

Shalchi

Fichtner

2008

ApJ

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Previous investigations of magnetic field line random walk and charged particle transport in turbulence mostly employed an axisymmetric turbulence model. However, real turbulence is assumed to be nonaxisymmetric. In this article we employ a simple model for nonaxisymmetric turbulence based on a very recent article. By analytically describing the random walk of magnetic field lines and by combining these results with a general compound transport model, we derive the cosmic-ray diffusion tensor. As demonstrated, the nonaxisymmetry leads to different components of the cosmic-ray diffusion tensor in the perpendicular direction. These new results are essential for several applications such as solar modulation studies.

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Suppression of Particle Drifts by Turbulence

Cited by 98 publications

References 27 publications

Drift Effects on the Galactic Cosmic Ray Modulation

Drift Effects on the Galactic Cosmic Ray Modulation

Modelling anomalous cosmic ray oxygen in the heliosheath

The Cosmic‐Ray Diffusion Tensor in Nonaxisymmetric Turbulence

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