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

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

doi:10.3390/atmos12040508

Cited by 8 publications

(5 citation statements)

References 53 publications

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“…The interaction between collisionless shocks and plasma turbulence is a key ingredient for the understanding of many astrophysical phenomena (e.g., Bykov et al 2019;Guo et al 2021). Such an interaction has been of growing interest in recent literature, involving theoretical (Zank et al 2002), numerical (Giacalone & Jokipii 1996;Guo & Giacalone 2012;Trotta et al 2021), and observational (Lario et al 2019;Pitňa et al 2017;Perri et al 2021) efforts.…”

Section: Introductionmentioning

confidence: 99%

On the Transmission of Turbulent Structures across the Earth’s Bow Shock

Trotta

Pecora

Settino

et al. 2022

ApJ

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Collisionless shocks and plasma turbulence are crucial ingredients for a broad range of astrophysical systems. The shock–turbulence interaction, and in particular the transmission of fully developed turbulence across the quasi-perpendicular Earth’s bow shock, is here addressed using a combination of spacecraft observations and local numerical simulations. An alignment between the Wind (upstream) and Magnetospheric Multiscale (downstream) spacecraft is used to study the transmission of turbulent structures across the shock, revealing an increase of their magnetic helicity content in its downstream. Local kinetic simulations, in which the dynamics of turbulent structures are followed through their transmission across a perpendicular shock, confirm this scenario, revealing that the observed magnetic helicity increase is associated with the compression of turbulent structures at the shock front.

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Section: Introductionmentioning

confidence: 99%

On the Transmission of Turbulent Structures across the Earth’s Bow Shock

Trotta

Pecora

Settino

et al. 2022

ApJ

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“…This choice is motivated by the fact that the particle pitch-angle scattering times, in the presence of magnetic turbulence or magnetic rotational discontinuities, are found to be characterized by power-law probability distributions [48][49][50][51][52]. Those probabilities exhibit a power-law behaviour over more than three decades both in the experimental data measured in the solar wind [48,50] and in the numerical simulations of particle transport either in a three-dimensional spectrum of magnetic fluctuations [49] or in the numerical study of the effects of magnetic rotational discontinuities [51].…”

Section: Time Fractional Derivatives and Lévy Walksmentioning

confidence: 99%

Energetic Particle Superdiffusion in Solar System Plasmas: Which Fractional Transport Equation?

2021

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Superdiffusive transport of energetic particles in the solar system and in other plasma environments is often inferred; while this can be described in terms of Lévy walks, a corresponding transport differential equation still calls for investigation. Here, we propose that superdiffusive transport can be described by means of a transport equation for pitch-angle scattering where the time derivative is fractional rather than integer. We show that this simply leads to superdiffusion in the direction parallel to the magnetic field, and we discuss some advantages with respect to approaches based on transport equations with symmetric spatial fractional derivates.

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“…They may also have a significant role in the energisation and transport of charged particles in the corona and interplanetary space (e.g. Manchester et al 2005;Perri et al 2021;Kilpua et al 2021a). A key feature of sheaths important for space weather considerations is their turbulent, compressed nature (Kilpua et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Structure and fluctuations of a slow ICME sheath observed at 0.5 au by the Parker Solar Probe

Kilpua

Good

Ala‐Lahti

et al. 2022

A&A

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Context. Sheath regions ahead of interplanetary coronal mass ejections (ICMEs) are compressed and turbulent global heliospheric structures. Their global and fine-scale structure are outstanding research problems, and only a few studies have been conducted on this topic closer to the Sun than 1 au. Comprehensive knowledge of the sheath structure and embedded fluctuations and of their evolution in interplanetary space is important for understanding their geoeffectiveness, their role in accelerating charged particles to high energies, the interaction of ICMEs with the ambient wind, and the transport of energy between boundaries. Aims. Our key aims are to investigate in detail the overall structure, as well as nature (stochastic, chaotic, or periodic) and origin, of magnetic fluctuations within a sheath ahead of a slow ICME in the inner heliosphere. Methods. We used magnetic field and plasma observations from the Parker Solar Probe (PSP) during a sheath region observed at ∼0.5 au on March 15, 2019, ahead of a slow and slowly expanding streamer blow-out CME bracketed between a slower and faster stream. To examine the magnetohydrodynamic-scale turbulent properties, we present an analysis of the fluctuation amplitudes, magnetic compressibility of fluctuations, partial variance of increments (PVI), normalised cross helicity (σc), and normalised residual energy (σr). We also conducted a Jensen-Shannon permutation entropy and complexity analysis. Results. The investigated sheath consisted of slower and faster flows that were separated by a brief (∼15 min) change in the magnetic sector bounded by current sheet crossings and a velocity shear zone. The fluctuation amplitudes and frequency of high PVI values were larger and higher throughout the sheath than in the upstream wind and had dominantly negative σr and strongly positive σc. The velocity shear region marked a strong increase in temperature and specific entropy, and the following faster flow had large local patches of positive σr as well as larger fluctuation amplitudes and higher PVI values, in particular at smaller timescales. Fluctuations in the preceding wind and in the sheath were found to be stochastic. However, sheath fluctuations showed lower entropy and higher complexity, with entropy showing a reducing and complexity an increasing trend with increasing time lag. Conclusions. The two-part sheath structure was likely a result of a warp in the heliospheric current sheet (HCS) that was swept up and compressed into the sheath. The driving ejecta accelerated and heated the wind at the back of the sheath, which then interacted with the slower wind ahead of the HCS warp. This also caused some distinct differences in fluctuation properties across the sheath. Sheaths of slow ICMEs originating as streamer blow-outs can thus have complex structure where fluctuation properties are not just downstream shock properties, but are generated within the sheath. At short timescales, fluctuations feature fully developed and imbalanced MHD turbulence, while at longer scales, fluctuations are increasingly dominated by intermittent coherent and ordered structures.

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

Cited by 8 publications

References 53 publications

On the Transmission of Turbulent Structures across the Earth’s Bow Shock

On the Transmission of Turbulent Structures across the Earth’s Bow Shock

Energetic Particle Superdiffusion in Solar System Plasmas: Which Fractional Transport Equation?

Structure and fluctuations of a slow ICME sheath observed at 0.5 au by the Parker Solar Probe

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