scholarly journals The Confinement of Galactic Cosmic Rays by Alfven Waves

1975 ◽  
Vol 170 (2) ◽  
pp. 251-260 ◽  
Author(s):  
J. A. Holmes ◽  
D. W. Sciama
Keyword(s):  
Cosmic Rays ◽  
Galactic Cosmic Rays ◽  
Alfven Waves ◽  
Alfvén Waves

scholarly journals The impact of astrophysical dust grains on the confinement of cosmic rays

2021 ◽  
Vol 502 (2) ◽  
pp. 2630-2644
Author(s):  
Jonathan Squire ◽  
Philip F Hopkins ◽  
Eliot Quataert ◽  
Philipp Kempski
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Alfven Waves ◽  
Feedback Mechanism ◽  
Alfvén Waves ◽  
Small Scale ◽  
Charged Dust ◽  
Dust Grains ◽  
The Impact

ABSTRACT We argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. For sub-GeV to ∼103 GeV cosmic rays, small-scale parallel Alfvén waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. If the dust is nearly stationary, as in the bulk of the interstellar medium, Alfvén waves are damped by dust. This will reduce the amplitude of Alfvén waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. In well-ionized regions, the dust damping rate is larger by a factor of ∼10 than other mechanisms that damp parallel Alfvén waves at the scales relevant for ∼GeV cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. In astrophysical situations in which the dust moves through the gas with super-Alfvénic velocities, Alfvén waves are rendered unstable, which could directly scatter cosmic rays. This interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. This mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei.

Magnetohydrodynamic plasma instability driven by Alfvén waves excited by cosmic rays

1984 ◽  
Vol 31 (2) ◽  
pp. 275-299 ◽  
Author(s):  
J. F. McKenzie ◽  
G. M. Webb
Keyword(s):  
Cosmic Rays ◽  
Thermal Plasma ◽  
Cosmic Ray ◽  
Nonlinear Damping ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Shock Acceleration ◽  
Alfvén Waves ◽  
Wave Growth ◽  
Streaming Instability

Hydrodynamical equations describing the mutual interaction of cosmic rays, thermal plasma, magnetic field and Alfvén waves scattering the cosmic rays used in cosmic ray shock acceleration theory (e.g. McKenzie & Völk 1982; Drury 1983; Webb 1983) are analysed for long-wavelength linear compressive instabilities. The Alfvén wave field may contain a pre-existing component as well as a component excited by the cosmic ray streaming instability. In the case of no Alfvén wave damping, adiabatic wave growth and Alfvén wave generation by the cosmic ray streaming instability, it is found that the backward propagating slow magneto-acoustic mode is driven convectively unstable by the pressure of the self-excited Alfvén waves, provided the thermal plasmaβis sufficiently large. The equations are also analysed for the case where the Alfvén wave growth is balanced by some nonlinear damping mechanisms. In the latter case both the forward and backward propagating slow magneto-acoustic modes may be driven unstable if the plasmaβis sufficiently small. The conditions under which the instabilities occur are delineated, and sample calculations of growth rates given. Possible applications of the instabilities to astrophysical situations are briefly discussed.

scholarly journals Time-Dependent Simulation of Cosmic-Ray Shocks, Including Alfvén Transport

1994 ◽  
Vol 142 ◽  
pp. 969-973
Author(s):  
T. W. Jones
Keyword(s):  
Diffusion Coefficient ◽  
Cosmic Rays ◽  
Wave Energy ◽  
Cosmic Ray ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Constant Diffusion Coefficient ◽  
Constant Diffusion ◽  
Transport Effects

AbstractTime evolution of plane, cosmic-ray modified shocks has been simulated numerically for the case with parallel magnetic fields. Computations were done in a “three-fluid” dynamical model incorporating cosmic-ray and Alfvén-wave energy transport equations. Nonlinear feedback from the cosmic rays and Alfvén waves is included in the equation of motion for the underlying plasma, as is the finite propagation speed and energy dissipation of the Alfvén waves. Exploratory results confirm earlier, steady state analyses that found these Alfvén transport effects to be potentially important when the upstream Alfvén speed and gas sound speeds are comparable. As noted earlier, Alfvén transport effects tend to reduce the transfer of energy through a shock from gas to energetic particles. These studies show as well that the timescale for modification of the shock is altered in nonlinear ways. It is clear, however, that the consequences of Alfvén transport are strongly model dependent and that both advection of cosmic rays by the waves and dissipation of wave energy in the plasma will be important to model correctly when quantitative results are needed. Comparison is made between simulations based on a constant diffusion coefficient and more realistic diffusion models allowing the diffusion coefficient to vary in response to changes in Alfvén wave intensity. No really substantive differences were found between them.Subject headings: cosmic rays — MHD — shock waves

scholarly journals Nonlinear Landau Damping of Alfven Waves and the Production and Propagation of Cosmic Rays

1981 ◽  
Vol 94 ◽  
pp. 255-256
Author(s):  
R. J. Stoneham
Keyword(s):  
Cosmic Rays ◽  
Phase Speed ◽  
Alfven Waves ◽  
Magnetized Plasma ◽  
Landau Damping ◽  
Alfvén Waves ◽  
Fermi Acceleration ◽  
Image Position ◽  
Hydromagnetic Waves ◽  
The Waves

The existence of hydromagnetic waves (waves whose frequency ω is less than the ion gyrofrequency Ωi = eB/mic) in a collisionless magnetized plasma with β, the ratio of plasma pressure to magnetic pressure, much greater than unity is required in theories for Fermi acceleration of cosmic rays by converging scattering centres at a shock front, in theories for the adiabatic cooling of cosmic rays due to trapping by plasma instabilities in an expanding supernova remnant (Kulsrud and Zweibel 1975, Schwartz and Skilling 1978) and in theories for resonant scattering of cosmic rays by hydromagnetic waves in the hot phase of the interstellar medium (Holman et al. 1979). Hydromagnetic waves may be damped by thermal ion cyclotron damping for wavenumbers k≳Ωi/vi, where vi = (Ti/mi)1/2 is the average thermal ion speed, and by linear Landau damping for non-zero angles of propagation with respect to the ambient magnetic field (Foote and Kulsrud 1979). Damping by both these processes is strong in a high-β plasma where there are many particles travelling at the phase speed of the waves. Hydromagnetic waves propagating along may be damped by nonlinear wave-particle interactions, the most important of which is thermal ion Landau damping of the beat wave of two Alfvén waves. This nonlinear process has the effect of transferring energy from the waves to the particles and can therefore be considered as a damping process for the waves.

scholarly journals Evolution of Supernova Remnants with Cosmic Rays and Radiative Cooling

1994 ◽  
Vol 142 ◽  
pp. 841-844
Author(s):  
E. A. Dorfi
Keyword(s):  
Cosmic Rays ◽  
Thermal Plasma ◽  
Supernova Remnants ◽  
Numerical Models ◽  
High Energy ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Radiative Cooling ◽  
Fermi Acceleration ◽  
Wave Heating

AbstractRecent numerical models for SNR evolution are presented, including first-order Fermi acceleration with injection of suprathermal particles at the shock wave, heating due to dissipation of Alfvén waves in the precursor region and radiative cooling of the thermal plasma. The X-ray fluxes obtained from these SNR models show significant differences depending on the acceleration efficiency of cosmic rays. γ-ray fluxes are calculated originating from π0-decay of pions generated by collisions of the high-energy particles with the thermal plasma. Cooling of the thermal plasma and dissipation of Alfvén waves in the precursor are important to determine the final amount of the explosion energy ESN which is transferred into cosmic rays.Subject headings: acceleration of particles — cosmic rays — gamma rays: theory — shock waves — supernova remnants

scholarly journals The Role of Cosmic Rays and Alfvén Waves in the Structure of the Galactic Halo

1990 ◽  
Vol 140 ◽  
pp. 185-186
Author(s):  
M. K. Dougherty ◽  
J. F. Mckenzie
Keyword(s):  
Cosmic Rays ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Alfven Waves ◽  
Hydrostatic Equilibrium ◽  
Alfvén Waves ◽  
Galactic Disc ◽  
Plasma Distribution ◽  
Hydrostatic Model

The effect that cosmic rays and the Alfvén waves generated by them have on the structure of the plasma distribution perpendicular to the galactic disc in a hydrostatic model is examined. It is shown that the plasma distribution exhibits two length scales, essentially because the cosmic rays and Alfvén waves lift the gas up and stretch it out beyond the galactic plane. The predicted gas density far from the galactic plane indicates that models involving hydrostatic equilibrium should be replaced by those allowing for a galactic wind.

scholarly journals Damping of self generated Alfvén waves in a partially ionized medium and the grammage of cosmic rays in the proximity of supernova remnants

2021 ◽  
Author(s):  
Sarah Recchia ◽  
Daniele Galli ◽  
Lara Nava ◽  
Marco Padovani ◽  
Stefano Gabici ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Supernova Remnants ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Partially Ionized
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