Evidence of Superdiffusive Transport of Electrons Accelerated at Interplanetary Shocks

Perri, S.; Zimbardo, G.

doi:10.1086/525523

Cited by 89 publications

(93 citation statements)

References 35 publications

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“…In a series of papers, Perri & Zimbardo (2007, 2009a have shown that anomalous, superdiffusive transport of energetic particles accelerated at interplanetary shocks is indeed possible. Those analyses were based on the observation that at few hours upstream of the shocks the energetic particle time profiles are power laws rather than exponentials, the latter being predicted by DSA.…”

Section: Introductionmentioning

confidence: 99%

Parameter estimation of superdiffusive motion of energetic particles upstream of heliospheric shocks

Perri

Zimbardo

Effenberger

et al. 2015

A&A

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Context. In-situ spacecraft observations recently suggested that the transport of energetic particles accelerated at heliospheric shocks can be anomalous, i.e. the mean square displacement can grow non-linearly in time. In particular, a new analysis technique has permitted the study of particle transport properties from energetic particle time profiles upstream of interplanetary shocks. Indeed, the time/spatial power laws of the differential intensity upstream of several shocks are indicative of superdiffusion. Aims. A complete determination of the key parameters of superdiffusive transport comprises the power-law index, the superdiffusion coefficient, the related transition scale at which the energetic particle profiles turn to decay as power laws, and the energy spectral index of the shock accelerated particles. Methods. Assuming large-scale spatial homogeneity of the background plasma, the power-law behaviour can been derived from both a (microscopic) propagator formalism and a (macroscopic) fractional transport equation. We compare the two approaches and find a relation between the diffusion coefficients used in the two formalisms. Based on the assumption of superdiffusive transport, we quantitatively derive these parameters by studying energetic particle profiles observed by the Ulysses and Voyager 2 spacecraft upstream of shocks in the heliosphere, for which a superdiffusive particle transport has previously been observed. Further, we have jointly studied the electron energy spectra, comparing the values of the spectral indices observed with those predicted by the standard diffusive shock acceleration theory and by a model based on superdiffusive transport. Results. For a number of interplanetary shocks and for the solar wind termination shock, for the first time we obtain the anomalous diffusion constants and the scale at which the probability of particle free paths changes to a power-law. The investigation of the particle energy spectra indicates that a shock acceleration theory based on superdiffusive transport better explains observed spectral index values. Conclusions. This study, together with the analysis of energetic particles upstream of shock waves, allows us to fully determine the transport properties of accelerated particles, even in the case of superdiffusion. This represents a new powerful tool to understand the transport and acceleration processes at astrophysical shocks.

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Section: Introductionmentioning

confidence: 99%

Parameter estimation of superdiffusive motion of energetic particles upstream of heliospheric shocks

Perri

Zimbardo

Effenberger

et al. 2015

A&A

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“…Recently, Lazarian & Yan (2014) have demonstrated that the divergence of the magnetic field on scales less than the injection scale of the turbulence induces superdiffusion of cosmic rays (CRs) in the direction perpendicular to the mean magnetic field. The possibility of CR acceleration at interplanetary shocks in the regime of superdiffusive transport also has been shown by Perri & Zimbardo (2007, 2008, 2009a. The effect of superdiffusion has also been observed in numerical simulations by Xu & Yan (2013) and Roh et al (2016) for the particles accelerated by the shock mechanism.…”

Section: Introductionmentioning

confidence: 71%

Anomalous Galactic Cosmic Rays in the Framework of AMS-02

Khiali

Haino

Feng

2017

ApJ

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The cosmic ray energy spectra of protons and helium nuclei, which are the most abundant components of cosmic radiation, exhibit a remarkable hardening at energies above one hundred GeV/nucleon. Recent data from AMS-02 confirms this feature with a higher significance. This data challenges the current models of cosmic ray acceleration in Galactic sources and propagation in the Galaxy. Here, we explain the observed break in the spectra of proton and helium nuclei in light of recent advances of cosmic ray diffusion theories in turbulent astrophysical sources as a result of a transition between different cosmic ray diffusion regimes. We reconstruct the observed cosmic ray spectra using the fact that transition from normal diffusion to superdiffusion changes the efficiency of particle acceleration and causes the change in the spectral index. We find that calculated proton and helium spectra match very well with the data.

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“…In particular, other systems with coherent structures and/or strong spatio-temporal correlations are likely to exhibit similar non-diffusive and non-local transport dynamics. For example, there is observational evidence of superdiffusive transport of electrons accelerated at interplanetary shocks at corotating interaction regions (CIRs) (Perri and Zimbardo, 2007) and observational evidence of ion superdiffusion at the solar wind termination shock (Perri and Zimbardo, 2009). It would be interesting to explore the application of the ideas and techniques discussed here to these systems.…”

Section: Discussionmentioning

confidence: 99%

Non-diffusive, non-local transport in fluids and plasmas

Del-Castillo-Negrete

2010

Nonlin. Processes Geophys.

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Abstract.A review of non-diffusive transport in fluids and plasmas is presented. In the fluid context, nondiffusive chaotic transport by Rossby waves in zonal flows is studied following a Lagrangian approach. In the plasma physics context the problem of interest is test particle transport in pressure-gradient-driven plasma turbulence. In both systems the probability density function (PDF) of particle displacements is strongly non-Gaussian and the statistical moments exhibit super-diffusive anomalous scaling. Fractional diffusion models are proposed and tested in the quantitative description of the non-diffusive Lagrangian statistics of the fluid and plasma problems. Also, fractional diffusion operators are used to construct non-local transport models exhibiting up-hill transport, multivalued flux-gradient relations, fast pulse propagation phenomena, and "tunneling" of perturbations across transport barriers.

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Evidence of Superdiffusive Transport of Electrons Accelerated at Interplanetary Shocks

Cited by 89 publications

References 35 publications

Parameter estimation of superdiffusive motion of energetic particles upstream of heliospheric shocks

Parameter estimation of superdiffusive motion of energetic particles upstream of heliospheric shocks

Anomalous Galactic Cosmic Rays in the Framework of AMS-02

Non-diffusive, non-local transport in fluids and plasmas

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