Scatter-free acceleration of particles by interaction with plasma shock waves in the interstellar medium

2021 ◽  
Vol 503 (2) ◽  
pp. 2195-2202
Author(s):  
P Rashed-Mohassel ◽  
M Ghorbanalilu
Keyword(s):  
Magnetic Field ◽  
Shock Waves ◽  
Test Particle ◽  
Magnetic Trapping ◽  
Acceleration Of Particles ◽  
Acceleration Mechanism ◽  
Spiral Path ◽  
Interacting Particle ◽  
Background Magnetic Field ◽  
Plasma Shock

ABSTRACT Scatter-free acceleration is investigated for a test particle thrusted by a moving magnetized cloud in the presence of the uniform interstellar magnetic field. It is found that depending on the orientation of the background magnetic field, three different scenarios occur for the interacting particle. In some cases, the particle reflects into space with a negligible increase in energy. Otherwise, the particle is either trapped at the wavefront or is injected inside the cloud. The trapped particle moves with the cloud and gains energy through the magnetic trapping acceleration mechanism, which is already investigated in previous reports. The injected particle accelerates through a different mechanism, which is introduced in this paper as the spiral acceleration. In this mechanism, the particle moves in a spiral path and gains energy by the convective electric field of the cloud. The radius of the spiral increases as the particle gains more energy and the process continues until the particle is located inside the cloud. Since in most cases the trapping condition is not satisfied, the spiral acceleration mechanism is of great importance.

Particle acceleration by interstellar plasma shock waves in non-uniform background magnetic field

2020 ◽  
Vol 498 (4) ◽  
pp. 5517-5523
Author(s):  
P Rashed-Mohassel ◽  
M Ghorbanalilu
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Waves ◽  
Electric Field ◽  
Background Field ◽  
Magnetized Plasma ◽  
Background Magnetic Field ◽  
Positive Variation ◽  
Uniform Background ◽  
Plasma Shock

ABSTRACT Particle acceleration by plasma shock waves is investigated for a magnetized plasma cloud propagating in a non-uniform background magnetic field by means of analytical and numerical calculations. The mechanism studied here is mainly, magnetic trapping acceleration (MTA) which is previously investigated for a cloud moving through the uniform interstellar magnetic field (IMF). In this work, the acceleration is studied for a cloud moving in an antiparallel background field with spatial variations along the direction of motion. For negative variation, the cloud moves towards an antiparallel magnetic field with an increasing intensity, the trapped particle moves to locations with higher convective electric field and therefore gains more energy over time. For positive variation, the background field decreases to zero and changes into a parallel field with an increasing intensity. It is concluded that, when the background field vanishes, the MTA mechanism ceases and the particle escapes into the space. This leads to a bouncing acceleration which further increases energy of the gyrating particle. The two processes are followed by a shock drift acceleration, where due to the background magnetic field gradient, the particle drifts along the electric field and gains energy. Although for positive variation, three different mechanisms are involved, energy gain is less than in the case of a uniform background field.

scholarly journals Stochastic re-acceleration and magnetic-field damping in Tycho’s supernova remnant

2020 ◽  
Vol 639 ◽  
pp. A124
Author(s):  
A. Wilhelm ◽  
I. Telezhinsky ◽  
V. V. Dwarkadas ◽  
M. Pohl
Keyword(s):  
Magnetic Field ◽  
Supernova Remnant ◽  
Cosmic Ray ◽  
Shock Acceleration ◽  
Acceleration Of Particles ◽  
X Rays ◽  
Stochastic Acceleration ◽  
Broadband Spectrum ◽  
Background Magnetic Field ◽  
Particle Spectra

Context. Tycho’s supernova remnant (SNR) is associated with the historical supernova (SN) event SN 1572 of Type Ia. The explosion occurred in a relatively clean environment, and was visually observed, providing an age estimate. This SNR therefore represents an ideal astrophysical test-bed for the study of cosmic-ray acceleration and related phenomena. A number of studies suggest that shock acceleration with particle feedback and very efficient magnetic-field amplification combined with Alfvénic drift are needed to explain the rather soft radio spectrum and the narrow rims observed in X-rays. Aims. We show that the broadband spectrum of Tycho’s SNR can alternatively be well explained when accounting for stochastic acceleration as a secondary process. The re-acceleration of particles in the turbulent region immediately downstream of the shock should be efficient enough to impact particle spectra over several decades in energy. The so-called Alfvénic drift and particle feedback on the shock structure are not required in this scenario. Additionally, we investigate whether synchrotron losses or magnetic-field damping play a more profound role in the formation of the non-thermal filaments. Methods. We solved the full particle transport equation in test-particle mode using hydrodynamic simulations of the SNR plasma flow. The background magnetic field was either computed from the induction equation or follows analytic profiles, depending on the model considered. Fast-mode waves in the downstream region provide the diffusion of particles in momentum space. Results. We show that the broadband spectrum of Tycho can be well explained if magnetic-field damping and stochastic re-acceleration of particles are taken into account. Although not as efficient as standard diffusive shock acceleration, stochastic acceleration leaves its imprint on the particle spectra, which is especially notable in the emission at radio wavelengths. We find a lower limit for the post-shock magnetic-field strength ∼330 μG, implying efficient amplification even for the magnetic-field damping scenario. Magnetic-field damping is necessary for the formation of the filaments in the radio range, while the X-ray filaments are shaped by both the synchrotron losses and magnetic-field damping.

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

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 508
Author(s):  
Silvia Perri ◽  
Giuseppe Prete ◽  
Francesco Malara ◽  
Francesco Pucci ◽  
Gaetano Zimbardo
Keyword(s):  
Magnetic Field ◽  
Shock Waves ◽  
Transport Properties ◽  
Particle Transport ◽  
Energetic Particle ◽  
Parallel Transport ◽  
Magnetic Turbulence ◽  
Background Magnetic Field ◽  
Field Fluctuations ◽  
Energetic Particle Transport

Energetic particles are ubiquitous in the interplanetary space and their transport properties are strongly influenced by the interaction with magnetic field fluctuations. Numerical experiments have shown that transport in both the parallel and perpendicular directions with respect to the background magnetic field is deeply affected by magnetic turbulence spectral properties. Recently, making use of a numerical model with three dimensional isotropic turbulence, the influence of turbulence intermittency and magnetic fluctuations on the energetic particle transport was investigated in the solar wind context. Stimulated by this previous theoretical work, here we analyze the parallel transport of supra-thermal particles upstream of interplanetary shock waves by using in situ particle flux measurements; the aim was to relate particle transport properties to the degree of intermittency of the magnetic field fluctuations and to their relative amplitude at the energetic particle resonant scale measured in the same regions. We selected five quasi-perpendicular and five quasi-parallel shock crossings by the ACE satellite. The analysis clearly shows a tendency to find parallel superdiffusive transport at quasi-perpendicular shocks, with a significantly higher level of the energetic particle fluxes than those observed in the quasi-parallel shocks. Furthermore, the occurrence of anomalous parallel transport is only weakly related to the presence of magnetic field intermittency.

Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

1977 ◽  
Vol 17 (1) ◽  
pp. 93-103 ◽  
Author(s):  
N. F. Cramer
Keyword(s):  
Magnetic Field ◽  
Parametric Excitation ◽  
Acoustic Waves ◽  
Magnetic Pressure ◽  
Gas Pressure ◽  
Alfven Wave ◽  
Fast Wave ◽  
Magnetoacoustic Waves ◽  
Background Magnetic Field ◽  
The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

On the existence of compressional MHD oscillations in an inhomogeneous magnetoplasma

1990 ◽  
Vol 44 (2) ◽  
pp. 361-375 ◽  
Author(s):  
Andrew N. Wright
Keyword(s):  
Magnetic Field ◽  
Wave Equation ◽  
Density Distribution ◽  
Cold Plasma ◽  
Wave Equations ◽  
Perturbation Field ◽  
Plasma Density Distribution ◽  
Background Magnetic Field ◽  
Transverse Fields ◽  
The Magnetic Field

In a cold plasma the wave equation for solely compressional magnetic field perturbations appears to decouple in any surface orthogonal to the background magnetic field. However, the compressional fields in any two of these surfaces are related to each other by the condition that the perturbation field b be divergence-free. Hence the wave equations in these surfaces are not truly decoupled from one another. If the two solutions happen to be ‘matched’ (i.e. V.b = 0) then the medium may execute a solely compressional oscillation. If the two solutions are unmatched then transverse fields must evolve. We consider two classes of compressional solutions and derive a set of criteria for when the medium will be able to support pure compressional field oscillations. These criteria relate to the geometry of the magnetic field and the plasma density distribution. We present the conditions in such a manner that it is easy to see if a given magnetoplasma is able to executive either of the compressional solutions we investigate.

Schwinger effect in an instanton background with electric and magnetic fields via holography

2018 ◽  
Vol 33 (25) ◽  
pp. 1850144
Author(s):  
Maryam Gholizadeh Arashti ◽  
Majid Dehghani
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Production Rate ◽  
Pair Creation ◽  
Zero Temperature ◽  
Expectation Value ◽  
Background Magnetic Field ◽  
Electric And Magnetic Fields ◽  
Schwinger Effect ◽  
Horizon Limit

The Schwinger effect in the presence of instantons and background magnetic field was considered to study the dependence of critical electric field on instanton density and magnetic field using AdS/CFT conjecture. The gravity side is the near horizon limit of D3[Formula: see text]D(−[Formula: see text]1) background with electric and magnetic fields on the brane. Our approach is based on the potential analysis for particle–antiparticle pair at zero and finite temperatures, where the zero temperature case is a semi-confining theory. We find that presence of instantons suppresses the pair creation effect, similar to a background magnetic field. Then, the production rate will be obtained numerically using the expectation value of circular Wilson loop. The obtained production rate in a magnetic field is in agreement with previous results.

Plasma instabilities driven by pickup ions of ring-beam velocity distributions in the outer heliosheath 

2021 ◽  
Author(s):  
Ameneh Mousavi ◽  
Kaijun Liu ◽  
Sina Sadeghzadeh
Keyword(s):  
Magnetic Field ◽  
Maximum Growth ◽  
Dispersion Analysis ◽  
Maximum Growth Rate ◽  
Injection Velocity ◽  
Plasma Instabilities ◽  
Pickup Ions ◽  
Beam Velocity ◽  
Background Magnetic Field ◽  
Hybrid Simulations

<p><span>The stability of the pickup ions in the outer heliosheath has been studied by many researchers because of its relevance to the energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary EXplorer. However, previous studies are primarily limited to pickup ions of near </span><span>90° </span><span>pickup angles, the angle between the pickup ion injection velocity and the background, local interstellar magnetic field. Investigations on pickup ions of smaller pickup angles are still lacking. In this paper, linear kinetic dispersion analysis and hybrid simulations are carried out to examine the plasma instabilities driven by pickup ions of ring-beam velocity distributions at various pickup angles between zero and </span><span>90°</span><span>. </span><span>Parallel propagating waves are studied in the parameter regime where the parallel thermal spread of the pickup ions falls into the Alfvén cyclotron stability gap. </span><span>The linear analysis results and hybrid simulations both show that the fastest growing modes are the right-hand helicity waves propagating in the direction of the background magnetic field, and the maximum growth rate occurs at the pickup angle of </span><span>82°</span><span>. The simulation results further reveal that the saturation level of the fluctuating magnetic fields for pickup angles below </span><span>45° </span><span>is higher than that for pickup angles above </span><span>45°</span><span>. So, the scattering of pickup ions at near zero pickup angles is likely more pronounced than that at near </span><span>90° </span><span>pickup angles</span> .</p>

HelioSwarm: The Nature of Turbulence in Space Plasmas

2021 ◽  
Author(s):  
Harlan Spence ◽  
Kristopher Klein ◽  
HelioSwarm Science Team
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Large Scale ◽  
Solar Wind Plasma ◽  
Turbulent Energy ◽  
Space Plasmas ◽  
Plasma Parameters ◽  
Astrophysical Plasmas ◽  
Ion Distributions ◽  
Background Magnetic Field

<p>Recently selected for phase A study for NASA’s Heliophysics MidEx Announcement of Opportunity, the HelioSwarm Observatory proposes to transform our understanding of the physics of turbulence in space and astrophysical plasmas by deploying nine spacecraft to measure the local plasma and magnetic field conditions at many points, with separations between the spacecraft spanning MHD and ion scales.  HelioSwarm resolves the transfer and dissipation of turbulent energy in weakly-collisional magnetized plasmas with a novel configuration of spacecraft in the solar wind. These simultaneous multi-point, multi-scale measurements of space plasmas allow us to reach closure on two science goals comprised of six science objectives: (1) reveal how turbulent energy is transferred in the most probable, undisturbed solar wind plasma and distributed as a function of scale and time; (2) reveal how this turbulent cascade of energy varies with the background magnetic field and plasma parameters in more extreme solar wind environments; (3) quantify the transfer of turbulent energy between fields, flows, and ion heat; (4) identify thermodynamic impacts of intermittent structures on ion distributions; (5) determine how solar wind turbulence affects and is affected by large-scale solar wind structures; and (6) determine how strongly driven turbulence differs from that in the undisturbed solar wind. </p>

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