scholarly journals Interstellar Hydroxyl Masers in the Galaxy. II. Zeeman Pairs and the Galactic Magnetic Field

2003 ◽  
Vol 596 (1) ◽  
pp. 328-343 ◽  
Author(s):  
Vincent L. Fish ◽  
Mark J. Reid ◽  
Alice L. Argon ◽  
Karl M. Menten
Keyword(s):  
Magnetic Field ◽  
Galactic Magnetic Field ◽  
The Galaxy ◽  
Hydroxyl Masers

scholarly journals LIGHT SUPERCONDUCTING STRINGS IN THE GALAXY

2007 ◽  
Vol 16 (12b) ◽  
pp. 2399-2405 ◽  
Author(s):  
FRANCESC FERRER ◽  
TANMAY VACHASPATI
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Particle Physics ◽  
Milky Way ◽  
Gamma Ray ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Magnetic Field ◽  
The Galaxy ◽  
Intense Source

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.

scholarly journals Progress in the Global Modeling of the Galactic Magnetic Field

2019 ◽  
Vol 210 ◽  
pp. 04005 ◽  
Author(s):  
Michael Unger ◽  
Glennys Farrar
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Synchrotron Emission ◽  
Ultrahigh Energy ◽  
Galactic Magnetic Field ◽  
Global Modeling ◽  
Emission Data ◽  
The Galaxy ◽  
Ultrahigh Energy Cosmic Rays ◽  
The Impact

We discuss the global modeling of the properties of the Galactic Magnetic Field (GMF). Several improvements and variations of the model of the GMF from Jansson & Farrar (2012) (JF12) are investigated in an analysis constrained by all-sky rotation measures of extragalactic sources and polarized and unpolarized synchrotron emission data from WMAP and Planck. We present the impact of the investigated model variations on the propagation of ultrahigh-energy cosmic rays in the Galaxy

scholarly journals F. Magnetic Fields, Pulsars, X-Ray And Gamma-Ray Emission

1985 ◽  
Vol 19 (1) ◽  
pp. 431-435
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Gamma Ray ◽  
Logarithmic Spiral ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
The Galaxy ◽  
Magnetic Field Model ◽  
Characteristic Features

During the triennium under review many papers reported on studies of the structure of the galactic magnetic field. Andreasyan used rotation measures (RM) of large samples of extra-galactic radio sources and pulsars (29.156.001) or radio sources (32.156.002), and Inoue and Tabara (31.156.011) used in addition optical polarization of stars to investigate the direction of the large-scale regular magnetic field. Thomson and Nelson analyse the RMs of 459 extragalactic sources (32. 161.001) to determine the best fit parameters for a galactic magnetic-field model, and find agreement with their earlier work using pulsars (27.156.009). Similarly, Sofue and Fujimoto (33.155.011) show that the characteristic features of the RM distribution on the sky are well reproduced by a model in which the magnetic field is in a bisymmetric, two-armed logarithmic spiral configuration. Finally, Welter, Perry and Kronberg (37.159.096) present a statistical analysis of the (Galaxy-corrected) residual rotation measure (RRM) of 116 QSOs.

scholarly journals The effects of drift and winds on the propagation of Galactic cosmic rays

2021 ◽  
Author(s):  
A AL-Zetoun ◽  
A Achterberg
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Field Model ◽  
Galactic Cosmic Rays ◽  
Galactic Magnetic Field ◽  
Galactic Wind ◽  
Wind Speeds ◽  
Field Diffusion ◽  
The Galaxy ◽  
Magnetic Field Model

Abstract We study the effects of drift motions and the advection by a Galactic wind on the propagation of cosmic rays in the Galaxy. We employ a simplified magnetic field model, based on (and similar to) the Jansson-Farrar model for the Galactic magnetic field. Diffusion is allowed to be anisotropic. The relevant equations are solved numerically, using a set of stochastic differential equations. Inclusion of drift and a Galactic wind significantly shortens the residence time of cosmic rays, even for moderate wind speeds.

scholarly journals The Galactic Magnetic Field and Cosmic Rays

1970 ◽  
Vol 23 (5) ◽  
pp. 731 ◽  
Author(s):  
JH Piddington
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Local System ◽  
Galactic Magnetic Field ◽  
Galactic Field ◽  
General Field ◽  
The Galaxy ◽  
Coronal Field ◽  
The Magnetic Field

The structure of the magnetic field of the Galaxy and other spiral systems and the inseparable problem of the origin of cosmic rays are examined: (1) A variety of evidence is used to show that the galactic field extends far beyond the disk and connects the disk field with a general field fixed in the local system of galaxies. (2) The coronal field extends beyond 10 kpc as an oblique helix which is constantly expanding, and has partially force�free characteristics.

scholarly journals A more detailed look at Galactic magnetic field models: using free–free absorption in HII regions

2020 ◽  
Vol 636 ◽  
pp. A2
Author(s):  
I. M. Polderman ◽  
M. Haverkorn ◽  
T. R. Jaffe
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Low Frequency ◽  
Hii Regions ◽  
Synchrotron Emission ◽  
Galactic Magnetic Field ◽  
Measured Intensity ◽  
The Galaxy ◽  
Third Dimension ◽  
Absorption Measurements

Context. Cosmic rays (CRs) and the Galactic magnetic field (GMF) are fundamental actors in many processes in the Milky Way. The observed interaction product of these actors is Galactic synchrotron emission integrated over the line of sight (LOS). A comparison to simulations can be made with this tracer using existing GMF models and CR density models. This probes the GMF strength and morphology and the CR density. Aims. Our aim is to provide insight into the Galactic CR density and the distribution and morphology of the GMF strength by exploring and explaining the differences between the simulations and observations of synchrotron intensity. Methods. At low radio frequencies HII regions become opaque due to free–free absorption. Using these HII regions we can measure the synchrotron intensity over a part of the LOS through the Galaxy. The measured intensity per unit path length, that is, the emissivity, for HII regions at different distances, allows us to probe the variation in synchrotron emission not only across the sky but also in the third dimension of distance. Performing these measurements on a large scale is one of the new applications of the window opened by current low-frequency arrays. Using a number of existing GMF models in conjunction with the Galactic CR modeling code GALPROP, we can simulate these synchrotron emissivities. Results. We present an updated catalog, compiled from the literature, of low-frequency absorption measurements of HII regions, their distances, and electron temperatures. We report a simulated emissivity that shows a compatible trend for HII regions that are near the observer. However, we observe a systematically increasing synchrotron emissivity for HII regions that are far from the observer, which is not compatible with the values simulated by the GMF models and GALPROP. Conclusions. Current GMF models plus a GALPROP generated CR density model cannot explain low-frequency absorption measurements. One possibility is that distances to all HII regions catalogued at the kinematic “far” distance are erroneously determined, although this is unlikely since it ignores all evidence for far distances in the literature. However, a detection bias due to the nature of this tracer requires us to keep in mind that certain sources may be missed in an observation. The other possibilities are an enhanced emissivity in the outer Galaxy or a diminished emissivity in the inner Galaxy.

scholarly journals Measuring ISM fields using Pulsars

2008 ◽  
Vol 4 (S259) ◽  
pp. 15-24
Author(s):  
Aristeidis Noutsos
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Continuous Improvement ◽  
Clear Picture ◽  
Galactic Magnetic Field ◽  
Analysis Methods ◽  
The Galaxy ◽  
Invaluable Tool ◽  
The Magnetic Field

AbstractThe sample of available Galactic pulsar rotation measures has proven an invaluable tool for measuring the direction and magnitude of the interstellar magnetic fields of our Galaxy. In this review, I present highlights of recent efforts to measure and map the Galactic magnetic field using pulsars. I give an overview of the analysis methods that were used by previous authors and underline the key results that have given us a clear picture of the magnetic field in certain regions of the Galaxy. This review also lays out the limitations of the present analysis methods and the observational difficulties that have so far hindered the study of the Galactic magnetic field with pulsars. Despite these difficulties, the continuous discovery of new pulsars in more and more sensitive surveys offer a continuous improvement on the existing knowledge of the Galactic magnetic field.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Structure in the radiation of the galactic disk

1967 ◽  
Vol 31 ◽  
pp. 355-356
Author(s):  
R. D. Davies
Keyword(s):  
Magnetic Field ◽  
Galactic Disk ◽  
Galactic Magnetic Field ◽  
Measured Polarization

Observations at various frequencies between 136 and 1400 MHz indicate a considerable amount of structure in the galactic disk. This result appears consistent both with measured polarization percentages and with considerations of the strength of the galactic magnetic field.

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