scholarly journals Kinetic turbulence in shining pair plasma: intermittent beaming and thermalization by radiative cooling

2020 ◽  
Vol 493 (1) ◽  
pp. 603-626 ◽  
Author(s):  
Vladimir Zhdankin ◽  
Dmitri A Uzdensky ◽  
Gregory R Werner ◽  
Mitchell C Begelman
Keyword(s):  
Particle Acceleration ◽  
Crab Nebula ◽  
Reaction Force ◽  
Radiation Reaction ◽  
High Energy ◽  
Energetic Particles ◽  
Particle Energy ◽  
Radiative Cooling ◽  
Energy Distributions ◽  
Pair Plasma

ABSTRACT High-energy astrophysical systems frequently contain collision-less relativistic plasmas that are heated by turbulent cascades and cooled by emission of radiation. Understanding the nature of this radiative turbulence is a frontier of extreme plasma astrophysics. In this paper, we use particle-in-cell simulations to study the effects of external inverse Compton radiation on turbulence driven in an optically thin, relativistic pair plasma. We focus on the statistical steady state (where injected energy is balanced by radiated energy) and perform a parameter scan spanning from low magnetization to high magnetization (0.04 ≲ σ ≲ 11). We demonstrate that the global particle energy distributions are quasi-thermal in all simulations, with only a modest population of non-thermal energetic particles (extending the tail by a factor of ∼2). This indicates that non-thermal particle acceleration (observed in similar non-radiative simulations) is quenched by strong radiative cooling. The quasi-thermal energy distributions are well fit by analytic models in which stochastic particle acceleration (due to, e.g. second-order Fermi mechanism or gyroresonant interactions) is balanced by the radiation reaction force. Despite the efficient thermalization of the plasma, non-thermal energetic particles do make a conspicuous appearance in the anisotropy of the global momentum distribution as highly variable, intermittent beams (for high magnetization cases). The beamed high-energy particles are spatially coincident with intermittent current sheets, suggesting that localized magnetic reconnection may be a mechanism for kinetic beaming. This beaming phenomenon may explain rapid flares observed in various astrophysical systems (such as blazar jets, the Crab nebula, and Sagittarius A*).

scholarly journals Solar flares and energetic particles

2012 ◽  
Vol 370 (1970) ◽  
pp. 3241-3268 ◽  
Author(s):  
Nicole Vilmer
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Interplanetary Medium ◽  
High Energy ◽  
Energetic Particles ◽  
Efficient Production ◽  
X Rays ◽  
Radio Waves ◽  
Magnetic Structures ◽  
Available Information

Solar flares are now observed at all wavelengths from γ -rays to decametre radio waves. They are commonly associated with efficient production of energetic particles at all energies. These particles play a major role in the active Sun because they contain a large amount of the energy released during flares. Energetic electrons and ions interact with the solar atmosphere and produce high-energy X-rays and γ -rays. Energetic particles can also escape to the corona and interplanetary medium, produce radio emissions (electrons) and may eventually reach the Earth's orbit. I shall review here the available information on energetic particles provided by X-ray/γ-ray observations, with particular emphasis on the results obtained recently by the mission Reuven Ramaty High-Energy Solar Spectroscopic Imager. I shall also illustrate how radio observations contribute to our understanding of the electron acceleration sites and to our knowledge on the origin and propagation of energetic particles in the interplanetary medium. I shall finally briefly review some recent progress in the theories of particle acceleration in solar flares and comment on the still challenging issue of connecting particle acceleration processes to the topology of the complex magnetic structures present in the corona.

scholarly journals Comptonization by reconnection plasmoids in black hole coronae I: Magnetically dominated pair plasma

2021 ◽  
Author(s):  
Navin Sridhar ◽  
Lorenzo Sironi ◽  
Andrei M Beloborodov
Keyword(s):  
Black Holes ◽  
High Energy ◽  
Particle Energy ◽  
X Rays ◽  
Particle In Cell ◽  
Pair Plasma ◽  
Electron Positron ◽  
High Energy Tail ◽  
Hard State ◽  
Magnetic Tension

Abstract We perform two-dimensional particle-in-cell simulations of reconnection in magnetically dominated electron-positron plasmas subject to strong Compton cooling. We vary the magnetization σ ≫ 1, defined as the ratio of magnetic tension to plasma inertia, and the strength of cooling losses. Magnetic reconnection under such conditions can operate in magnetically dominated coronae around accreting black holes, which produce hard X-rays through Comptonization of seed soft photons. We find that the particle energy spectrum is dominated by a peak at mildly relativistic energies, which results from bulk motions of cooled plasmoids. The peak has a quasi-Maxwellian shape with an effective temperature of ∼100 keV, which depends only weakly on the flow magnetization and the strength of radiative cooling. The mean bulk energy of the reconnected plasma is roughly independent of σ, whereas the variance is larger for higher magnetizations. The spectra also display a high-energy tail, which receives ∼25 per cent of the dissipated reconnection power for σ = 10 and ∼40 per cent for σ = 40. We complement our particle-in-cell studies with a Monte Carlo simulation of the transfer of seed soft photons through the reconnection layer, and find the escaping X-ray spectrum. The simulation demonstrates that Comptonization is dominated by the bulk motions in the chain of Compton-cooled plasmoids and, for σ ∼ 10, yields a spectrum consistent with the typical hard state of accreting black holes.

scholarly journals Particle Acceleration in Gamma-Ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 475-482
Author(s):  
J.G. Kirk
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Front ◽  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Magnetic Field Generation ◽  
Relativistic Shocks ◽  
The Crab Nebula

SummarySimple kinematic theories of particle acceleration at relativistic shocks lead to the prediction of a high-energy spectral index of −1.1 for the energy flux of synchrotron photons. However, several effects can change this picture. In this paper I discuss the effect of magnetic field generation at the shock front and, by analogy with the Crab Nebula, suggest that an intrinsic break in the injection spectrum should be expected where the electron gyro radius is comparable to that of protons thermalized by the shock.

scholarly journals Scaling of magnetic dissipation and particle acceleration in ABC fields

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Qiang Chen ◽  
Krzysztof Nalewajko ◽  
Bhupendra Mishra
Keyword(s):  
Particle Acceleration ◽  
Magnetic Energy ◽  
Electric Energy ◽  
System Size ◽  
High Energy ◽  
Particle Energy ◽  
Growth Time ◽  
Two Dimensional ◽  
Energy Fraction ◽  
High Energy Part

Using particle-in-cell numerical simulations with electron–positron pair plasma, we study how the efficiencies of magnetic dissipation and particle acceleration scale with the initial coherence length $\lambda _0$ in relation to the system size $L$ of the two-dimensional ‘Arnold–Beltrami–Childress’ (ABC) magnetic field configurations. Topological constraints on the distribution of magnetic helicity in two-dimensional systems, identified earlier in relativistic force-free simulations, that prevent the high- $(L/\lambda _0)$ configurations from reaching the Taylor state, limit the magnetic dissipation efficiency to about $\epsilon _{\textrm {diss}} \simeq 60\,\%$ . We find that the peak growth time scale of the electric energy $\tau _{E,{\textrm {peak}}}$ scales with the characteristic value of initial Alfvén velocity $\beta _{A,{\textrm {ini}}}$ like $\tau _{E,\textrm {peak}} \propto (\lambda _0/L)\beta _{A,{\textrm {ini}}}^{-3}$ . The particle energy change is decomposed into non-thermal and thermal parts, with non-thermal energy gain dominant only for high initial magnetisation. The most robust description of the non-thermal high-energy part of the particle distribution is that the power-law index is a linear function of the initial magnetic energy fraction.

scholarly journals Particle Energization in Relativistic Plasma Turbulence: Solenoidal versus Compressive Driving

2021 ◽  
Vol 922 (2) ◽  
pp. 172
Author(s):  
Vladimir Zhdankin
Keyword(s):  
Particle Acceleration ◽  
Electric Fields ◽  
Large Scale ◽  
High Energy ◽  
Particle Energy ◽  
Density Fluctuations ◽  
Driving Mechanism ◽  
Ion Temperature ◽  
Driving Mechanisms ◽  
Particle Energization

Abstract Many high-energy astrophysical systems contain magnetized collisionless plasmas with relativistic particles, in which turbulence can be driven by an arbitrary mixture of solenoidal and compressive motions. For example, turbulence in hot accretion flows may be driven solenoidally by the magnetorotational instability or compressively by spiral shock waves. It is important to understand the role of the driving mechanism on kinetic turbulence and the associated particle energization. In this work, we compare particle-in-cell simulations of solenoidally driven turbulence with similar simulations of compressively driven turbulence. We focus on plasma that has an initial beta of unity, relativistically hot electrons, and varying ion temperature. Apart from strong large-scale density fluctuations in the compressive case, the turbulence statistics are similar for both drives, and the bulk plasma is described reasonably well by an isothermal equation of state. We find that nonthermal particle acceleration is more efficient when turbulence is driven compressively. In the case of relativistically hot ions, both driving mechanisms ultimately lead to similar power-law particle energy distributions, but over a different duration. In the case of nonrelativistic ions, there is significant nonthermal particle acceleration only for compressive driving. Additionally, we find that the electron-to-ion heating ratio is less than unity for both drives, but takes a smaller value for compressive driving. We demonstrate that this additional ion energization is associated with the collisionless damping of large-scale compressive modes via perpendicular electric fields.

scholarly journals Quantum effects on radiation friction driven magnetic field generation

2021 ◽  
Vol 136 (2) ◽  
Author(s):  
Tatyana V. Liseykina ◽  
Andrea Macchi ◽  
Sergey V. Popruzhenko
Keyword(s):  
Magnetic Field ◽  
Reaction Force ◽  
Three Dimensional ◽  
Quantum Effects ◽  
Radiation Reaction ◽  
High Energy ◽  
Joint Effect ◽  
Field Energy ◽  
Magnetic Field Generation ◽  
The Magnetic Field

AbstractRadiation losses in the interaction of superintense circularly polarized laser pulses with high-density plasmas can lead to the generation of strong quasistatic magnetic fields via absorption of the photon angular momentum (so-called inverse Faraday effect). To achieve the magnetic field strength of several Giga Gauss, laser intensities $$\simeq 10^{24}\;\mathrm {W/cm}^2$$ ≃ 10 24 W / cm 2 are required which brings the interaction to the border between the classical and the quantum regimes. We improve the classical modeling of the laser interaction with overcritical plasma in the “hole boring” regime by using a modified radiation friction force accounting for quantum recoil and spectral cut-off at high energies. The results of analytical calculations and three-dimensional particle-in-cell simulations show that, in foreseeable scenarios, the quantum effects may lead to a decrease in the conversion rate of laser radiation into high-energy photons by a factor 2–3. The magnetic field amplitude is suppressed accordingly, and the magnetic field energy—by more than one order in magnitude. This quantum suppression is shown to reach a maximum at a certain value of intensity and does not grow with the further increase in intensities. The non-monotonic behavior of the quantum suppression factor results from the joint effect of the longitudinal plasma acceleration and the radiation reaction force. The predicted features could serve as a suitable diagnostic for radiation friction theories.

scholarly journals Kinetic simulations of relativistic magnetic reconnection with synchrotron and inverse Compton cooling

2018 ◽  
Vol 84 (3) ◽  
Author(s):  
Krzysztof Nalewajko ◽  
Yajie Yuan ◽  
Martyna Chruślińska
Keyword(s):  
Magnetic Reconnection ◽  
Temperature Profile ◽  
Radiation Reaction ◽  
High Energy ◽  
Momentum Equation ◽  
Pair Plasma ◽  
Radiation Spectra ◽  
Inverse Compton ◽  
First Results ◽  
Order Of Magnitude

First results are presented from kinetic numerical simulations of relativistic collisionless magnetic reconnection in a pair plasma that include radiation reaction from both synchrotron and inverse Compton (IC) processes, motivated by non-thermal high-energy astrophysical sources, including in particular blazars. These simulations are initiated from a configuration known as ‘ABC fields’ that evolves due to coalescence instability and generates thin current layers in its linear phase. Global radiative efficiencies, instability growth rates, time-dependent radiation spectra, lightcurves, variability statistics and the structure of current layers are investigated for a broad range of initial parameters. We find that the IC radiative signatures are generally similar to the synchrotron signatures. The luminosity ratio of IC to synchrotron spectral components, the Compton dominance, can be modified by more than one order of magnitude with respect to its nominal value. For very short cooling lengths, we find evidence for modification of the temperature profile across the current layers, no systematic compression of plasma density and very consistent profiles of the scalar product$\boldsymbol{E}\boldsymbol{\cdot }\boldsymbol{B}$of electric field$\boldsymbol{E}$and magnetic field$\boldsymbol{B}$. We decompose the profiles of$\boldsymbol{E}\boldsymbol{\cdot }\boldsymbol{B}$with the use of the Vlasov momentum equation, demonstrating a contribution from radiation reaction at the thickness scale consistent with the temperature profile.

Radiation-reaction force on a moving mirror

1993 ◽  
Vol 3 (11) ◽  
pp. 2151-2159 ◽  
Author(s):  
Claudia Eberlein
Keyword(s):  
Reaction Force ◽  
Radiation Reaction ◽  
Radiation Reaction Force

Incompleteness of General Relativity, Einstein's Errors, and Related Experiments-- American Physical Society March meeting, Z23 5, 2015 --

2015 ◽  
Vol 8 (2) ◽  
pp. 2135-2147 ◽  
Author(s):  
C. Y. Lo
Keyword(s):  
General Relativity ◽  
Einstein Equation ◽  
Reaction Force ◽  
Radiation Reaction ◽  
Gravitational Energy ◽  
Energy Conditions ◽  
Experimental Investigations ◽  
Positive Mass Theorem ◽  
Wave Source ◽  
Photonic Energy

General relativity is incomplete since it does not include the gravitational radiation reaction force and the interaction of gravitation with charged particles. General relativity is confusing because Einstein's covariance principle is invalid in physics. Moreover, there is no bounded dynamic solution for the Einstein equation. Thus, Gullstrand is right and the 1993 Nobel Prize for Physics press release is incorrect. Moreover, awards to Christodoulou reflect the blind faith toward Einstein and accumulated errors in mathematics. Note that the Einstein equation with an electromagnetic wave source has no valid solution unless a photonic energy-stress tensor with an anti-gravitational coupling is added. Thus, the photonic energy includes gravitational energy. The existence of anti-gravity coupling implies that the energy conditions in space-time singularity theorems of Hawking and Penrose cannot be satisfied, and thus are irrelevant. Also, the positive mass theorem of Yau and Schoen is misleading, though considered as an achievement by the Fields Medal. E = mc2 is invalid for the electromagnetic energy alone. The discovery of the charge-mass interaction establishes the need for unification of electromagnetism and gravitation and would explain many puzzles. Experimental investigations for further results are important.

The two-body problem: an effective-one-body approach

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Body Problem ◽  
Equations Of Motion ◽  
Reaction Force ◽  
Kerr Black Hole ◽  
Radiation Reaction ◽  
Spherically Symmetric ◽  
Geodesic Motion ◽  
Two Body Problem ◽  
Symmetric Spacetime ◽  
Radiation Reaction Force

This chapter presents the basics of the ‘effective-one-body’ approach to the two-body problem in general relativity. It also shows that the 2PN equations of motion can be mapped. This can be done by means of an appropriate canonical transformation, to a geodesic motion in a static, spherically symmetric spacetime, thus considerably simplifying the dynamics. Then, including the 2.5PN radiation reaction force in the (resummed) equations of motion, this chapter provides the waveform during the inspiral, merger, and ringdown phases of the coalescence of two non-spinning black holes into a final Kerr black hole. The chapter also comments on the current developments of this approach, which is instrumental in building the libraries of waveform templates that are needed to analyze the data collected by the current gravitational wave detectors.

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