scholarly journals Nonthermal Radiation from Clusters of Galaxies: The Role of Merger Shocks in Particle Acceleration

2003 ◽  
Vol 583 (2) ◽  
pp. 695-705 ◽  
Author(s):  
Stefano Gabici ◽  
Pasquale Blasi
Keyword(s):  
Particle Acceleration ◽  
Clusters Of Galaxies ◽  
Nonthermal Radiation

scholarly journals The Role of Wide Field X-ray Surveys in Astronomy

2012 ◽  
Vol 10 (H16) ◽  
pp. 669-670
Author(s):  
Richard D. Saxton
Keyword(s):  
High Variability ◽  
Wide Field ◽  
Clusters Of Galaxies ◽  
Tidal Disruption ◽  
X Ray ◽  
Sky Survey ◽  
History Of ◽  
X Ray Background ◽  
Rare Classes

AbstractWe review the history of X-ray sky surveys from the early experiments to the catalogues of 105 sources produced by ROSAT, Chandra and XMM-Newton. At bright fluxes the X-ray sky is shared between stars, accreting binaries and extragalactic sources while deeper surveys are dominated by AGN and clusters of galaxies. The X-ray background, found by the earliest missions, has been largely resolved into discrete sources at soft (0.3-2 keV) energies but at higher energies an important fraction still escapes detection. The possible identification of the missing flux with Compton-thick AGN has been probed in recent years by Swift and Integral.Variability seen in objects observed at different epochs has proved to be an excellent discriminator for rare classes of objects. The comparison of ROSAT All Sky Survey (RASS) and ROSAT pointed observations identified several Novae and high variability AGN as well as initiating the observational study of Tidal Disruption events. More recently the XMM-Newton slew survey, in conjunction with archival RASS data, has detected further examples of flaring objects which have been followed-up in near-real time at other wavelengths.

scholarly journals Theoretical Implications of Diffuse Non-Thermal Emission from Clusters of Galaxies

2002 ◽  
Vol 199 ◽  
pp. 141-148
Author(s):  
T.A. Enßlin
Keyword(s):  
Thermal Emission ◽  
Extreme Ultraviolet ◽  
Short Review ◽  
Radio Galaxies ◽  
High Energy ◽  
Clusters Of Galaxies ◽  
Thermal Electron ◽  
Electron Population ◽  
X Ray

A short review on theoretical implications of non-thermal emission (radio, extreme ultraviolet, high energy X-ray) from the intra-cluster medium is given. The origin of cluster radio halos and cluster radio relics is discussed within the framework of a network of processes producing a non-thermal electron population. Emphasis is given to the role of old, remnant, presently invisible relativistic plasma released by former radio galaxies.

scholarly journals The Sun as a Stellar Laboratory: Unsolved Problems

2004 ◽  
Vol 219 ◽  
pp. 1-10
Author(s):  
John C. Brown
Keyword(s):  
Particle Acceleration ◽  
Solar Physics ◽  
High Energy ◽  
Atmospheric Plasma ◽  
Energy Budgets ◽  
The Sun ◽  
Stellar Flare ◽  
Neupert Effect ◽  
Kinetic Effects

A brief overview is given of some of the current outstanding problems in solar physics with greatest emphasis on high energy phenomena in the atmosphere. The importance of plasma kinetic effects, as well as MHD, in understanding the complex finely structured and dynamic solar atmospheric plasma is stressed. Key results from the RHESSI Mission on energetic flare particle acceleration, propagation, and flare energy budgets are presented as are recent findings concerning the solar and stellar flare Neupert effect and the possible role of energetic particles in micro-events in the ‘non-flaring’ sun. Finally, evidence showing that magnetic fields are also important in hot star phenomena is mentioned.

scholarly journals Magnetic self-compression in laboratory plasmas, quasars and radio galaxies. Part I

1986 ◽  
Vol 4 (2) ◽  
pp. 193-213 ◽  
Author(s):  
Eric J. Lerner
Keyword(s):  
Rotational Velocity ◽  
Radio Galaxies ◽  
Plasma Cloud ◽  
Clusters Of Galaxies ◽  
Laboratory Plasma ◽  
Radiated Power ◽  
Laboratory Plasmas ◽  
Quasars And Radio Galaxies ◽  
Good Agreement

A model of quasars and their associated jets as phenomena of magnetic selfcompression is presented. Magnetic field self-compression, as observed in laboratory plasma focus devices, results in increases in energy density of more than 108 and in even larger increases in transferred power density. Our model, based on the scaling of these phenomena to astrophysical dimensions, avoids the problems of gravitationallyconfined approaches. It presents a mechanism by which the energy of a quasar is immediately derived from a volume nearly 106 times larger than the observed quasar radiating volume and is ultimately derived from the volume of an entire protogalactic plasma cloud. The model's predictions of quasar energy, radiated power, lifetime, dimensions, density and rotational velocity are in good agreement with observations. Part II of this paper extends the model to radio galaxies and briefly discusses the role of similar self-compression processes in the origin of filamentary super-clusters of galaxies.

scholarly journals Flare particle acceleration in the interaction of twisted coronal flux ropes

2018 ◽  
Vol 611 ◽  
pp. A40 ◽  
Author(s):  
J. Threlfall ◽  
A. W. Hood ◽  
P. K. Browning
Keyword(s):  
Particle Acceleration ◽  
Solar Flares ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Uniform Background ◽  
Energy Gains ◽  
Particle Behaviour

Aim. The aim of this work is to investigate and characterise non-thermal particle behaviour in a three-dimensional (3D) magnetohydrodynamical (MHD) model of unstable multi-threaded flaring coronal loops.Methods. We have used a numerical scheme which solves the relativistic guiding centre approximation to study the motion of electrons and protons. The scheme uses snapshots from high resolution numerical MHD simulations of coronal loops containing two threads, where a single thread becomes unstable and (in one case) destabilises and merges with an additional thread.Results. The particle responses to the reconnection and fragmentation in MHD simulations of two loop threads are examined in detail. We illustrate the role played by uniform background resistivity and distinguish this from the role of anomalous resistivity using orbits in an MHD simulation where only one thread becomes unstable without destabilising further loop threads. We examine the (scalable) orbit energy gains and final positions recovered at different stages of a second MHD simulation wherein a secondary loop thread is destabilised by (and merges with) the first thread. We compare these results with other theoretical particle acceleration models in the context of observed energetic particle populations during solar flares.

scholarly journals The Galaxy Mass Distribution from Mergers in a Collapsing Spherical Cluster

1996 ◽  
Vol 171 ◽  
pp. 444-444
Author(s):  
Nir J. Shaviv ◽  
Giora Shaviv
Keyword(s):  
Numerical Method ◽  
Mass Distribution ◽  
Combined Effect ◽  
Radial Position ◽  
Clusters Of Galaxies ◽  
Spherical Cluster ◽  
The Galaxy ◽  
Self Gravity

We examine the role of mergers in the formation and statistics of galaxies and clusters of galaxies. First steps in this direction were carried out by Shaviv & Shaviv (1993, ApJ.Lett., 412, L25) where the OD case was treated. The work is extended to examine the effect of self gravity. Thus, we essentially explore the combined effect of violent relaxation and mergers on the resulting structure and mass distribution of galaxies in clusters of galaxies. We developed a numerical method to treat the spherical 2D problem (radial position and velocity) of the evolution of a collapsing cluster of gas clouds (Shaviv & Shaviv, 1995, ApJ., 448, 514).

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