DISTANCE INDICATORS OF GAMMA-RAY PULSARS

2013 ◽  
Vol 23 ◽  
pp. 289-294
Author(s):  
WEI WANG
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Physical Origin ◽  
Large Area ◽  
Distance Measurements ◽  
Distance Information ◽  
Cascade Processes ◽  
Gamma Ray Emission ◽  
Distance Indicators ◽  
The Magnetic Field

Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.

scholarly journals The distance indicators in gamma-ray pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 546-548
Author(s):  
Wei Wang
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Physical Origin ◽  
Large Area ◽  
Distance Measurements ◽  
Distance Information ◽  
Cascade Processes ◽  
Gamma Ray Emission ◽  
Distance Indicators ◽  
The Magnetic Field

AbstractDistance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η=Lγ/Ė) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between η and ζ3, the generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between η and BLC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.

scholarly journals Interpolation of externally-caused magnetic fields over large sparse arrays using Spherical Elementary Current Systems

2010 ◽  
Vol 28 (9) ◽  
pp. 1795-1805 ◽  
Author(s):  
S. A. McLay ◽  
C. D. Beggan
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Current System ◽  
Electrical Current ◽  
Ionospheric Currents ◽  
Large Area ◽  
Physically Based ◽  
Subsurface Current ◽  
Current Systems ◽  
The Magnetic Field

Abstract. A physically-based technique for interpolating external magnetic field disturbances across large spatial areas can be achieved with the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the ionosphere. The magnetic field recorded at observatories can be used to invert for the electrical currents, which can subsequently be employed to interpolate or extrapolate the magnetic field across a large area. We show that, in addition to the ionospheric currents, inverting for induced subsurface current systems can result in strong improvements to the estimate of the interpolated magnetic field. We investigate the application of the SECS method at mid- to high geomagnetic latitudes using a series of observatory networks to test the performance of the external field interpolation over large distances. We demonstrate that relatively few observatories are required to produce an estimate that is better than either assuming no external field change or interpolation using latitudinal weighting of data from two other observatories.

Influence of Permanent Magnets Installation Approach on the Torque of а Magneto-Rheological Disk Brake

2021 ◽  
Vol 105 ◽  
pp. 184-193
Author(s):  
Ilya Aleksandrovich Frolov ◽  
Andrei Aleksandrovich Vorotnikov ◽  
Semyon Viktorovich Bushuev ◽  
Elena Alekseevna Melnichenko ◽  
Yuri Viktorovich Poduraev
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Materials ◽  
Permanent Magnets ◽  
Magnetorheological Fluid ◽  
Simulation Modelling ◽  
Disc Brake ◽  
Large Area ◽  
Braking Torque ◽  
The Magnetic Field

Magnetorheological braking devices function due to the organization of domain structures between liquid and solid magnetic materials under the action of an electromagnetic or magnetic field. The disc is most widely used as a rotating braking element that made of a solid magnetic material due to the large area of contact with a magnetorheological fluid. Many factors affect the braking characteristics of the magnetorheological disc brake. Specifically, the value of the magnetic field and how the field is distributed across the work element is significantly affected at the braking torque. There are different ways to generate a magnetic field. In this study, the method of installation of permanent magnets into the construction, allowing to increase the braking torque of the magnetorheological disc brake is proposed. Simulation modelling showing the distribution of the magnetic field across the disk depending on the installation of permanent magnets with different pole orientations were carried out. The model takes into account the possibility of increasing the gap between solid magnetic materials of the structure, inside them which the magnetorheological fluid is placed. Comparative estimation of the distribution of the magnetic fields depending on the chosen method of installation of permanent magnets with different orientations of their poles is carried out. Further research is planned to focus on a comparative assessment of the distribution of magnetic fields depending on the selected material of the braking chamber.

scholarly journals Millimeter and Microwave Activity of the Sun

1990 ◽  
Vol 142 ◽  
pp. 457-465 ◽  
Author(s):  
M. R. Kundu ◽  
S. M. White
Keyword(s):  
Magnetic Field ◽  
Gamma Rays ◽  
Solar Flares ◽  
Gamma Ray ◽  
High Spatial Resolution ◽  
High Resolution Imaging ◽  
The Sun ◽  
Millimeter Wavelengths ◽  
Resolution Imaging ◽  
The Magnetic Field

The emission of solar flares at millimeter wavelengths is of great interest both in its own right and because it is generated by the energetic electrons which also emit gamma rays. Since high-resolution imaging at gamma-ray energies is not presently possible, millimeter observations can act as a substitute. Except for that class of flares known as gamma-ray flares the millimetric emission is optically thin. It can be used as a powerful diagnostic of the energy distribution of electrons in solar flares and its evolution, and of the magnetic field. We have carried out high-spatial-resolution millimeter observations of solar flares this year using the Berkeley-Illinois-Maryland Array (BIMA), and report on the preliminary results in this paper (Kundu et al 1990; White et al 1990). We also report some recent results obtained from multifrequency observations using the VLA (White et al 1990).

scholarly journals Search for dark matter signatures in the gamma-ray emission towards the Sun with the Fermi Large Area Telescope

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
M. N. Mazziotta ◽  
F. Loparco ◽  
D. Serini ◽  
A. Cuoco ◽  
P. De La Torre Luque ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gamma Ray ◽  
The Sun ◽  
Large Area ◽  
Gamma Ray Emission

scholarly journals Gamma-Ray Emission of the Kes 73/1E 1841-045 Region Observed with the Fermi Large Area Telescope

2017 ◽  
Vol 837 (1) ◽  
pp. 69 ◽  
Author(s):  
Paul K. H. Yeung ◽  
Albert K. H. Kong ◽  
P. H. Thomas Tam ◽  
C. Y. Hui ◽  
Jumpei Takata ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Large Area ◽  
Gamma Ray Emission

scholarly journals Analytical model for cluster radio relics

2020 ◽  
Vol 493 (2) ◽  
pp. 2306-2317 ◽  
Author(s):  
M Brüggen ◽  
F Vazza
Keyword(s):  
Magnetic Field ◽  
Flux Distribution ◽  
Cosmic Ray ◽  
Analytical Models ◽  
Physical Parameters ◽  
Mass Relation ◽  
Intracluster Medium ◽  
Large Area ◽  
Shock Dynamics ◽  
The Magnetic Field

ABSTRACT Radio relics are vast synchrotron sources that sit on the outskirts of merging galaxy clusters. In this work we model their formation using a Press–Schechter formalism to simulate merger rates, analytical models for the intracluster medium and the shock dynamics, as well as a simple model for the cosmic ray electrons at the merger shocks. We show that the statistical properties of the population of radio relics are strongly dependent on key physical parameters, such as the acceleration efficiency, the magnetic field strength at the relic, the geometry of the relic and the duration of the electron acceleration at merger shocks. It turns out that the flux distribution as well as the power–mass relation can constrain key parameters of the intracluster medium. With the advent of new large-area radio surveys, statistical analyses of radio relics will complement what we have learned from observations of individual objects.

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