Damping of Magnetohydrodynamic Turbulence in Partially Ionized Plasma: Implications for Cosmic Ray Propagation

Xu, Siyao; Yan, Huirong; Lazarían, A.

doi:10.3847/0004-637x/826/2/166

Cited by 73 publications

(65 citation statements)

References 89 publications

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“…The damping effects in a partially ionized medium mainly arise from the collisional friction between ions and neutrals, i.e., ion-neutral collisional damping (IN) and the viscosity in neutral fluid, i.e., neutral viscous damping (NV) (Lithwick and Goldreich, 2001;Lazarian, Vishniac, and Cho, 2004). Their relative importance depends on the turbulence and plasma parameters (Xu, Lazarian, and Yan, 2015;Xu, Yan, and Lazarian, 2016;Xu and Lazarian, 2017b). In super-Alfvénic turbulence with the turbulent energy larger than the magnetic energy, IN dominates over NV if the condition…”

Section: Mhd Turbulence In a Partially Ionized Mediummentioning

confidence: 99%

3D turbulent reconnection: Theory, tests, and astrophysical implications

Lazarían¹,

et al. 2020

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Magnetic reconnection, topological change in magnetic fields, is a fundamental process in magnetized plasmas. It is associated with energy release in regions of magnetic field annihilation, but this is only one facet of this process. Astrophysical fluid flows normally have very large Reynolds numbers and are expected to be turbulent, in agreement with observations. In strong turbulence magnetic field lines constantly reconnect everywhere and on all scales, thus making magnetic reconnection an intrinsic part of the turbulent cascade. We note in particular that this is inconsistent with the usual practice of regarding magnetic field lines as persistent dynamical elements. A number of theoretical, numerical, and observational studies starting with the Lazarian & Vishniac 1999 paper proposed that 3D turbulence makes magnetic reconnection fast and that magnetic reconnection and turbulence are intrinsically connected. In particular, we discuss the dramatic violation of the textbook concept of magnetic flux-freezing in the presence of turbulence. We demonstrate that in the presence of turbulence the plasma effects are subdominant to turbulence as far as the magnetic reconnection is concerned. The latter fact justifies an MHD-like treatment of magnetic reconnection on all scales much larger than the relevant plasma scales. We discuss numerical and observational evidence supporting the turbulent reconnection model. In particular, we demonstrate that the tearing reconnection is suppressed in 3D and, unlike the 2D settings, 3D reconnection induces turbulence that makes magnetic reconnection independent of resistivity. We show that turbulent reconnection dramatically affects key astrophysical processes, e.g. star formation, turbulent dynamo, acceleration of cosmic rays. We provide criticism of the concept of "reconnection-mediated turbulence" and explain why turbulent reconnection is very different from enhanced turbulent resistivity and hyper-resistivity, and why the latter have fatal conceptual flaws.

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Section: Mhd Turbulence In a Partially Ionized Mediummentioning

confidence: 99%

3D turbulent reconnection: Theory, tests, and astrophysical implications

Lazarían¹,

et al. 2020

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“…In the energy range E < E cf , the ASA dominates over the synchrotron cooling and leads to the electron energy spectrum as shown in Eq. (5). At higher energies, the synchrotron cooling plays a dominant role in shaping the electron energy spectrum.…”

Section: Synchrotron Spectrum Resulting From Both Asa and Synchrotronmentioning

confidence: 99%

Synchrotron spectra of GRB prompt emission and pulsar wind nebulae

2019

J. Phys.: Conf. Ser.

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Particle acceleration is a fundamental process in many high-energy astrophysical environments and determines the spectral features of their synchrotron emission. We have studied the adiabatic stochastic acceleration (ASA) of electrons arising from the basic dynamics of magnetohydrodynamic (MHD) turbulence and found that the ASA acts to efficiently harden the injected electron energy spectrum. The dominance of the ASA at low energies and the dominance of synchrotron cooling at high energies result in a broken power-law shape of both electron energy spectrum and photon synchrotron spectrum. Furthermore, we have applied the ASA to studying the synchrotron spectra of the prompt emission of gamma-ray bursts (GRBs) and pulsar wind nebulae (PWNe). The good agreement between our theories and observations confirms that the stochastic particle acceleration is indispensable in explaining their synchrotron emission.

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“…A series of works has successively investigated the propagation in hot ionized ISM (D' Angelo et al 2016, Nava et al 2019, warm ISM phases (Nava et al 2016, D'Angelo et al 2016, and atomic and molecular phases of ISM (Brahimi et al 2020). In ionized media the main damping processes for perturbations with wavelength in resonance with CR gyromotion are the linear and non-linear Landau damping and the effect of CR self-generated perturbations interaction with background turbulence (Farmer and Goldreich 2004), sometimes referred as the turbulent damping (Lazarian 2016), whereas ion-neutral collisions dominate in partially ionized media (Xu et al 2016) at least for large enough wavenumbers (Brahimi et al 2020). Particle propagation is investigated by solving a system of two coupled equations for the CR pressure P CR (E) and the self-generated wave magnetic energy I(k) (Nava et al 2016):…”

Section: Supernova Remnants and Superbubblesmentioning

confidence: 99%

“…However, close to a CR source if the CR overpressure is high enough or the CR current is strong enough CRs can trigger instabilities over times short enough to compensate over the ion-neutral damping time. This is especially true at CR energies beyond a few 100 GeV-1 TeV as in these energy regimes the MHD waves in resonance with the particles have a pulsation low enough to be in the coupled regime where ions and neutrals move together (Xu et al 2016, Brahimi et al 2020). Xu et al (2016) considered only the effect of background MHD turbulence injected at scales larger than the typical size of the phase under question.…”

Section: Cosmic Ray Propagation In Atomic and Molecular Interstellar mentioning

confidence: 99%

“…This is especially true at CR energies beyond a few 100 GeV-1 TeV as in these energy regimes the MHD waves in resonance with the particles have a pulsation low enough to be in the coupled regime where ions and neutrals move together (Xu et al 2016, Brahimi et al 2020). Xu et al (2016) considered only the effect of background MHD turbulence injected at scales larger than the typical size of the phase under question. The CR mean free path is found to be strongly reduced in the range 1-100 TeV in molecular clouds because of both gyro-resonant and transit-time damping interactions with MHD waves.…”

Section: Cosmic Ray Propagation In Atomic and Molecular Interstellar mentioning

confidence: 99%

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High-Energy Particles and Radiation in Star-Forming Regions

et al. 2020

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Non-thermal particles and high-energy radiation can play a role in the dynamical processes in star-forming regions and provide an important piece of the multiwavelength observational picture of their structure and components. Powerful stellar winds and supernovae in compact clusters of massive stars and OB associations are known to be favourable sites of high-energy particle acceleration and sources of non-thermal radiation and neutrinos. Namely, young massive stellar clusters are likely sources of the PeV (petaelectronvolt) regime cosmic rays (CRs). They can also be responsible for the cosmic ray composition, e.g., 22 Ne/ 20 Ne anomalous isotopic ratio in CRs. Efficient particle acceleration can be accompanied by super-adiabatic amplification of the fluctuating magnetic fields in the systems converting a part of kinetic power of the winds and supernovae into the magnetic energy through the CR-driven instabilities. The escape and CR propagation in the vicinity of the sources are affected by the non-linear CR feedback. These effects are expected to be important in starburst galaxies, which produce high-energy neutrinos and gamma-rays. We give a brief review of the theoreti-A. M. Bykov

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Damping of Magnetohydrodynamic Turbulence in Partially Ionized Plasma: Implications for Cosmic Ray Propagation

Cited by 73 publications

References 89 publications

3D turbulent reconnection: Theory, tests, and astrophysical implications

3D turbulent reconnection: Theory, tests, and astrophysical implications

Synchrotron spectra of GRB prompt emission and pulsar wind nebulae

High-Energy Particles and Radiation in Star-Forming Regions

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