scholarly journals The Nature of the Galactic Center Arc

1996 ◽  
Vol 169 ◽  
pp. 263-269 ◽  
Author(s):  
E. Serabyn
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Galactic Center ◽  
Magnetic Energy ◽  
Linear Structure ◽  
High Energy ◽  
Molecular Gas ◽  
Synchrotron Emission ◽  
Interferometric Imaging ◽  
Relativistic Particles

Ever since the Galactic Center Arc was resolved into its component filaments a decade ago, it has been clear that its linear structure arises from the influence of a strong magnetic field. However, the origin and nature of the contributory phenomena have remained elusive. Since what is seen is synchrotron emission from relativistic particles, of prime interest is a knowledge of the acceleration mechanism involved. Interferometric imaging of the molecular gas in the vicinity of the Arc has now provided a tantalizing clue to the Arc's origin: molecular clumps coinciding with the endpoints of a number of the Arc's filaments point to these clumps as the source of the relativistic particles. This suggests that as dense molecular clumps course through the ambient magnetic field at the Galactic Center, magnetic energy is liberated in their leading layers via field reconnection, precipitating rapid acceleration of free charges to high energy.

scholarly journals What are the Radio Filaments Near the Galactic Center?

1996 ◽  
Vol 169 ◽  
pp. 247-261 ◽  
Author(s):  
Mark Morris
Keyword(s):  
Magnetic Field ◽  
Galactic Center ◽  
Galactic Plane ◽  
Local Source ◽  
Flux Tubes ◽  
Flux Lines ◽  
Magnetic Flux Tubes ◽  
The Magnetic Field ◽  
Relativistic Particles ◽  
Projected Distance

A population of nonthermally-emitting radio filaments tens of parsecs in length has been observed within a projected distance of ∼130 pc of the Galactic center. More or less perpendicular to the Galactic plane, they appear to define the flux lines of a milligauss magnetic field. The characteristics of the known filaments are summarized. Three fundamental questions raised by these structures are discussed: 1) Do they represent magnetic flux tubes embedded within an ubiquitous, dipole magnetic field permeating the inner Galaxy, but which have been illuminated by some local source of relativistic particles, or are they instead isolated, self-sustaining current paths with an approximately force-free magnetic configuration in pressure equilibrium with the interstellar medium? 2) What is the source of either the magnetic field or the current? and 3) What is the source of the relativistic particles which provide the illuminating synchrotron radiation? We are nearer an answer to the the last of these questions than to the others, although several interesting models have been proposed.

scholarly journals Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

2016 ◽  
Vol 4 ◽  
Author(s):  
Y. J. Gu ◽  
Q. Yu ◽  
O. Klimo ◽  
T. Zh. Esirkepov ◽  
S. V. Bulanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Energy ◽  
Collisionless Plasma ◽  
High Energy ◽  
Field Energy ◽  
Displacement Current ◽  
Particle In Cell ◽  
Magnetic Field Energy ◽  
High Energy Electrons

Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.

scholarly journals COSMIC RAYS IN GALAXY CLUSTERS AND THEIR NONTHERMAL EMISSION

2014 ◽  
Vol 23 (04) ◽  
pp. 1430007 ◽  
Author(s):  
GIANFRANCO BRUNETTI ◽  
THOMAS W. JONES
Keyword(s):  
Cosmic Rays ◽  
Galaxy Clusters ◽  
High Energy ◽  
Synchrotron Emission ◽  
High Energies ◽  
Electrical Conductivities ◽  
Nonthermal Emission ◽  
Near Future ◽  
Nonthermal Emissions ◽  
Relativistic Particles

Radio observations prove the existence of relativistic particles and magnetic field associated with the intra-cluster-medium (ICM) through the presence of extended synchrotron emission in the form of radio halos and peripheral relics. This observational evidence has fundamental implications on the physics of the ICM. Nonthermal components in galaxy clusters are indeed unique probes of very energetic processes operating within clusters that drain gravitational and electromagnetic energy into cosmic rays (CRs) and magnetic fields. These components strongly affect the (micro-)physical properties of the ICM, including viscosity and electrical conductivities, and have also potential consequences on the evolution of clusters themselves. The nature and properties of CRs in galaxy clusters, including the origin of the observed radio emission on cluster-scales, have triggered an active theoretical debate in the last decade. Only recently we can start addressing some of the most important questions in this field, thanks to recent observational advances, both in the radio and at high energies. The properties of CRs and of cluster nonthermal emissions depend on the dynamical state of the ICM, the efficiency of particle acceleration mechanisms in the ICM and on the dynamics of these CRs. In this paper, we discuss in some detail the acceleration and transport of CRs in galaxy clusters and the most relevant observational milestones that have provided important steps on our understanding of this physics. Finally, looking forward to the possibilities from new generations of observational tools, we focus on what appear to be the most important prospects for the near future from radio and high-energy observations.

scholarly journals Turbulent dynamo in a collisionless plasma

2016 ◽  
Vol 113 (15) ◽  
pp. 3950-3953 ◽  
Author(s):  
François Rincon ◽  
Francesco Califano ◽  
Alexander A. Schekochihin ◽  
Francesco Valentini
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Energy ◽  
Collisionless Plasma ◽  
High Energy ◽  
Nearby Galaxy ◽  
Astrophysical Plasmas ◽  
Flow Energy ◽  
Field Amplification ◽  
Turbulent Dynamo

Magnetic fields pervade the entire universe and affect the formation and evolution of astrophysical systems from cosmological to planetary scales. The generation and dynamical amplification of extragalactic magnetic fields through cosmic times (up to microgauss levels reported in nearby galaxy clusters, near equipartition with kinetic energy of plasma motions, and on scales of at least tens of kiloparsecs) are major puzzles largely unconstrained by observations. A dynamo effect converting kinetic flow energy into magnetic energy is often invoked in that context; however, extragalactic plasmas are weakly collisional (as opposed to magnetohydrodynamic fluids), and whether magnetic field growth and sustainment through an efficient turbulent dynamo instability are possible in such plasmas is not established. Fully kinetic numerical simulations of the Vlasov equation in a 6D-phase space necessary to answer this question have, until recently, remained beyond computational capabilities. Here, we show by means of such simulations that magnetic field amplification by dynamo instability does occur in a stochastically driven, nonrelativistic subsonic flow of initially unmagnetized collisionless plasma. We also find that the dynamo self-accelerates and becomes entangled with kinetic instabilities as magnetization increases. The results suggest that such a plasma dynamo may be realizable in laboratory experiments, support the idea that intracluster medium turbulence may have significantly contributed to the amplification of cluster magnetic fields up to near-equipartition levels on a timescale shorter than the Hubble time, and emphasize the crucial role of multiscale kinetic physics in high-energy astrophysical plasmas.

scholarly journals High energy neutrino absorption by W production in a strong magnetic field

2010 ◽  
Vol 690 (4) ◽  
pp. 386-389 ◽  
Author(s):  
A.V. Kuznetsov ◽  
N.V. Mikheev ◽  
A.V. Serghienko
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
High Energy ◽  
High Energy Neutrino ◽  
Energy Neutrino ◽  
Neutrino Absorption

scholarly journals Diffuse Cluster-Wide Radio Halos

2002 ◽  
Vol 12 ◽  
pp. 516-518
Author(s):  
Haida Liang
Keyword(s):  
Magnetic Fields ◽  
High Energy ◽  
Synchrotron Emission ◽  
Gas Distribution ◽  
Seed Particles ◽  
High Energy Tail ◽  
Relativistic Particles ◽  
Radio Halos

AbstractWe will discuss the properties and origins of halos and relics including estimates of the cluster magnetic fields, and present results for a few recently discovered halos and relics. The electrons in the suprathermal high energy tail of the thermal gas distribution are likely to provide the seed particles for acceleration through mergers and turbulences to relativistic energies. These relativistic particles are then responsible for the synchrotron emission of the halos.

scholarly journals Revisiting the Distance to Radio Loops I and IV Using Gaia and Radio/Optical Polarization Data

2021 ◽  
Vol 922 (2) ◽  
pp. 210
Author(s):  
G. V. Panopoulou ◽  
C. Dickinson ◽  
A. C. S. Readhead ◽  
T. J. Pearson ◽  
M. W. Peel
Keyword(s):  
Magnetic Field ◽  
Galactic Center ◽  
Classical Method ◽  
Dust Emission ◽  
Galactic Latitude ◽  
Synchrotron Emission ◽  
Optical Polarization ◽  
The North ◽  
Significant Alignment ◽  
North Polar

Abstract Galactic synchrotron emission exhibits large angular scale features known as radio spurs and loops. Determining the physical size of these structures is important for understanding the local interstellar structure and for modeling the Galactic magnetic field. However, the distance to these structures is either under debate or entirely unknown. We revisit a classical method of finding the location of radio spurs by comparing optical polarization angles with those of synchrotron emission as a function of distance. We consider three tracers of the magnetic field: stellar polarization, polarized synchrotron radio emission, and polarized thermal dust emission. We employ archival measurements of optical starlight polarization and Gaia distances and construct a new map of polarized synchrotron emission from WMAP and Planck data. We confirm that synchrotron, dust emission, and stellar polarization angles all show a statistically significant alignment at high Galactic latitude. We obtain distance limits to three regions toward Loop I of 112 ± 17 pc, 135 ± 20 pc, and <105 pc. Our results strongly suggest that the polarized synchrotron emission toward the North Polar Spur at b > 30° is local. This is consistent with the conclusions of earlier work based on stellar polarization and extinction, but in stark contrast with the Galactic center origin recently revisited on the basis of X-ray data. We also obtain a distance measurement toward part of Loop IV (180 ± 15 pc) and find evidence that its synchrotron emission arises from chance overlap of structures located at different distances. Future optical polarization surveys will allow the expansion of this analysis to other radio spurs.

scholarly journals Tidal Disruption of Magnetars as the Sources of Fast Radio Burst

2020 ◽  
Author(s):  
Kushaal Kumar Pothula
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Strong Magnetic Field ◽  
Accretion Disk ◽  
High Energy ◽  
Tidal Disruption ◽  
High Energy Cosmic Rays ◽  
Tidal Forces ◽  
Fast Radio Burst ◽  
The Magnetic Field

Abstract Fast Radio Bursts (FRBs) are mysterious millisecond duration radio transients, and some FRBs repeat. FRBs are highly polarized, indicating that the source is within a strong magnetic field. I hypothesize their origin as Tidal Disruption Events (TDEs) of magnetars by black holes. The TDE releases energy stored in the magnetic field of the magnetar, producing an FRB. Occasionally the magnetar is disrupted into multiple debris chunks, and as individual chunks get consumed, multiple FRBs are produced, forming a repeating FRB. Another process of formation of repeating FRBs is starquakes on magnetars because of tidal forces from black holes. Due to the strong magnetic field of the accretion disk, the FRB is produced in jets. Sometimes the magnetar debris surrounding the magnetic field gets accelerated, producing Ultra-high energy cosmic rays, whose source remains unknown. The FRB signal produced gets polarized by the magnetosphere of the accretion disk and intergalactic magnetic fields.

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