scholarly journals FORMATION OF H i CLOUDS IN SHOCK-COMPRESSED INTERSTELLAR MEDIUM: PHYSICAL ORIGIN OF ANGULAR CORRELATION BETWEEN FILAMENTARY STRUCTURE AND MAGNETIC FIELD

2016 ◽  
Vol 833 (1) ◽  
pp. 10 ◽  
Author(s):  
Tsuyoshi Inoue ◽  
Shu-ichiro Inutsuka
Keyword(s):  
Magnetic Field ◽  
Interstellar Medium ◽  
Angular Correlation ◽  
Physical Origin ◽  
Filamentary Structure

scholarly journals Non-thermal filaments from the tidal destruction of clouds in the Galactic centre

2020 ◽  
Vol 501 (2) ◽  
pp. 1868-1877
Author(s):  
Eric R Coughlin ◽  
C J Nixon ◽  
Adam Ginsburg
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Particle Acceleration ◽  
Magnetic Reconnection ◽  
Molecular Clouds ◽  
Galactic Centre ◽  
Relativistic Electrons ◽  
Galactic Magnetic Field ◽  
Physical Origin ◽  
Filamentary Structure

ABSTRACT Synchrotron-emitting, non-thermal filaments (NTFs) have been observed near the Galactic centre for nearly four decades, yet their physical origin remains unclear. Here we investigate the possibility that NTFs are produced by the destruction of molecular clouds by the gravitational potential of the Galactic centre. We show that this model predicts the formation of a filamentary structure with length on the order of tens to hundreds of pc, a highly ordered magnetic field along the axis of the filament, and conditions conducive to magnetic reconnection that result in particle acceleration. This model therefore yields the observed magnetic properties of NTFs and a population of relativistic electrons, without the need to appeal to a dipolar, ∼mG, Galactic magnetic field. As the clouds can be both completely or partially disrupted, this model provides a means of establishing the connection between filamentary structures and molecular clouds that is observed in some, but not all, cases.

scholarly journals Constraining the coherence scale of the interstellar magnetic field using TeV gamma-ray observations of supernova remnants

2020 ◽  
Vol 496 (2) ◽  
pp. 2448-2461 ◽  
Author(s):  
Matteo Pais ◽  
Christoph Pfrommer ◽  
Kristian Ehlert ◽  
Maria Werhahn ◽  
Georg Winner
Keyword(s):  
Magnetic Field ◽  
Interstellar Medium ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Cosmic Rays ◽  
Shock Acceleration ◽  
Interstellar Gas ◽  
Narrow Angle ◽  
Magnetohydrodynamic Simulations ◽  
Tev Gamma Rays

ABSTRACT Galactic cosmic rays (CRs) are believed to be accelerated at supernova remnant (SNR) shocks. In the hadronic scenario, the TeV gamma-ray emission from SNRs originates from decaying pions that are produced in collisions of the interstellar gas and CRs. Using CR-magnetohydrodynamic simulations, we show that magnetic obliquity-dependent shock acceleration is able to reproduce the observed TeV gamma-ray morphology of SNRs such as Vela Jr and SN1006 solely by varying the magnetic morphology. This implies that gamma-ray bright regions result from quasi-parallel shocks (i.e. when the shock propagates at a narrow angle to the upstream magnetic field), which are known to efficiently accelerate CR protons, and that gamma-ray dark regions point to quasi-perpendicular shock configurations. Comparison of the simulated gamma-ray morphology to observations allows us to constrain the magnetic coherence scale λB around Vela Jr and SN1006 to $\lambda _B \simeq 13_{-4.3}^{+13}$ pc and $\lambda _B \gt 200_{-40}^{+50}$ pc, respectively, where the ambient magnetic field of SN1006 is consistent with being largely homogeneous. We find consistent pure hadronic and mixed hadronic-leptonic models that both reproduce the multifrequency spectra from the radio to TeV gamma-rays and match the observed gamma-ray morphology. Finally, to capture the propagation of an SNR shock in a clumpy interstellar medium, we study the interaction of a shock with a dense cloud with numerical simulations and analytics. We construct an analytical gamma-ray model for a core collapse SNR propagating through a structured interstellar medium, and show that the gamma-ray luminosity is only biased by 30 per cent for realistic parameters.

Magnetic Confinement and Control of Trajectories of Discharge Species in Atmospheric-Pressure Analytical Spark Discharges

1987 ◽  
Vol 41 (2) ◽  
pp. 200-207 ◽  
Author(s):  
Vahid Majidi ◽  
David M. Coleman
Keyword(s):  
Magnetic Field ◽  
Atmospheric Pressure ◽  
Magnetic Confinement ◽  
Post Discharge ◽  
Conducting Channel ◽  
Filamentary Structure ◽  
Spark Discharges ◽  
Time Space ◽  
Series Of Experiments ◽  
And Control

A series of experiments, designed to help characterize the behavior of an analytical spark discharge in an external pulsed magnetic field, is described. Results include controlled formation and deformation of a spark's post-discharge torus utilizing different magnetic field configurations. One manifestation of this research was discovery of a new filamentary structure which extends from the spark conducting channel to the magnet pole face(s). These features were investigated via their refracted light (Schlieren) and spectroscopic (time/space/wavelength-resolved) properties. Practical ramifications of this control are discussed.

MAGNETIC FIELD AMPLIFICATION BY RELATIVISTIC SHOCKS IN AN INHOMOGENEOUS MEDIUM

2012 ◽  
Vol 08 ◽  
pp. 364-367
Author(s):  
YOSUKE MIZUNO ◽  
MARTIN POHL ◽  
JACEK NIEMIEC ◽  
BING ZHANG ◽  
KEN-ICHI NISHIKAWA ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Inhomogeneous Medium ◽  
Magnetic Energy ◽  
Small Scale ◽  
Two Dimensional ◽  
Filamentary Structure ◽  
Field Amplification ◽  
Relativistic Shocks ◽  
Field Lines ◽  
Magnetohydrodynamic Simulations

We perform two-dimensional relativistic magnetohydrodynamic simulations of a mildly relativistic shock propagating through an inhomogeneous medium. We show that the postshock region becomes turbulent owing to preshock density inhomogeneity, and the magnetic field is strongly amplified due to the stretching and folding of field lines in the turbulent velocity field. The amplified magnetic field evolves into a filamentary structure in two-dimensional simulations. The magnetic energy spectrum is flatter than the Kolmogorov spectrum and indicates that the so-called small-scale dynamo is occurring in the postshock region. We also find that the amplitude of magnetic-field amplification depends on the direction of the mean preshock magnetic field.

Magnetic Field Draping of the Heliopause and Its Consequences for Radio Emission in the Very Local Interstellar Medium

2021 ◽  
Vol 917 (2) ◽  
pp. L20
Author(s):  
N. V. Pogorelov ◽  
F. Fraternale ◽  
T. K. Kim ◽  
L. F. Burlaga ◽  
D. A. Gurnett
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Interstellar Medium ◽  
Local Interstellar Medium

scholarly journals Could bow-shaped magnetic morphologies surround filamentary molecular clouds?

2019 ◽  
Vol 632 ◽  
pp. A68 ◽  
Author(s):  
M. Tahani ◽  
R. Plume ◽  
J. C. Brown ◽  
J. D. Soler ◽  
J. Kainulainen
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Magnetic Fields ◽  
Faraday Rotation ◽  
Molecular Clouds ◽  
Monte Carlo Analysis ◽  
Line Of Sight ◽  
Field Reversal ◽  
Filamentary Structure ◽  
Western Side

Context. A new method based on Faraday rotation measurements recently found the line-of-sight component of magnetic fields in Orion-A and showed that their direction changes from the eastern side of this filamentary structure to its western side. Three possible magnetic field morphologies that can explain this reversal across the Orion-A region are toroidal, helical, and bow-shaped morphologies. Aims. In this paper, we constructed simple models to represent these three morphologies and compared them with the available observational data to find the most probable morphology(ies). Methods. We compared the observations with the models and used probability values and a Monte Carlo analysis to determine the most likely magnetic field morphology among these three morphologies. Results. We found that the bow morphology had the highest probability values, and that our Monte-Carlo analysis suggested that the bow morphology was more likely. Conclusions. We suggest that the bow morphology is the most likely and the most natural of the three morphologies that could explain a magnetic field reversal across the Orion-A filamentary structure (i.e., bow, helical and toroidal morphologies).

scholarly journals Characteristics of the diffuse interstellar medium

1991 ◽  
Vol 147 ◽  
pp. 3-10
Author(s):  
D. P. Cox
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Interstellar Medium ◽  
Thick Disk ◽  
Thermal Pressure ◽  
Heating Mechanism ◽  
High Stage ◽  
Ob Associations

There have been several recent changes in perspective on the diffuse interstellar environment, including recognition of a thick disk of warm gas, cosmic rays, and magnetic field. In addition, evidence for a pervasive hot phase driven by supernova disruption has weakened to the point that a quasihomogeneous warm intercloud gas may occupy most of the interstellar volume at midplane, with individual bubbles created by supernovae and OB associations occupying perhaps 10 and 20 per cent respectively. The bubble population is sufficient to explain the high stage ions (0 VI, N V, C IV, perhaps Si IV) found in the disk, though possibly not those found at higher z. The estimated midplane pressure has increased, leaving the thermal pressure inside clouds almost negligible. The reduced porosity of the medium, its greater thickness, and its larger pressure all act to suppress fountain activity, either arising from the disk generally, or from the blowout of superbubbles. Finally, there appears to be a peculiar coincidence between the cloud heating mechanism and the activity determining the interstellar pressure.

scholarly journals Optical Polarization as a Probe of the Local Interstellar Medium

1984 ◽  
Vol 81 ◽  
pp. 145-148 ◽  
Author(s):  
J. Tinbergen
Keyword(s):  
Magnetic Field ◽  
Interstellar Medium ◽  
General Rule ◽  
Local Environment ◽  
Measurement Tool ◽  
Optical Polarization ◽  
Local Interstellar Medium ◽  
Instrumentation Design

The use of interstellar polarization as a measurement tool for dust or magnetic field presents practical difficulties (dust and magnetic field configurations inextricably mixed up; limited number of suitable stars). This general rule applies even more in the local environment, for which the polarizations are small and the influence of errors of observation changes in character. Because of this, the use of polarimetry and the design of polarimetric observing programmes for the local interstellar medium must be approached with even greater care than in the general case. I propose in this review to amplify this point, so that the reader can judge for himself to what extent he can use published results and can also, given the opportunity and instrumentation, design an observing programme that will really pay off.

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