scholarly journals Radiation Beaming in Pulsars

1971 ◽  
Vol 46 ◽  
pp. 455-456
Author(s):  
V. Canuto
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Coming Out ◽  
Critical Magnetic Field ◽  
Zero Field ◽  
Ordinary Wave ◽  
Magnetic Field Axis ◽  
Field Lines ◽  
Star Surface ◽  
The Magnetic Field

It is usually considered that the beaming of the radiation coming out of a pulsar has to be strictly connected with the mechanism producing the radiation itself. We want to show that even when the emitting mechanism gives rise to an isotropically distributed radiation, the presence of a strong magnetic field will automatically beam the radiation preferentially along the magnetic field line rather than in any other direction. We have computed the Compton scattering and from that the opacity KH (K0 is the opacity for zero field). In Figure 1 the ratio KH/K0 is given vs. θ, the angle between the propagation vector and the magnetic field axis. Hq is a critical magnetic field numerically equal to 4.41 × 1013 G; Ne is the electron density. For the ordinary wave the opacity is reduced at θ = 0, while it is unaffected at θ = π/2 where KH → K0. Even at θ = π/4 the ratio KH/K0 is still ≃ 10−2, and a good beaming is still present. The values of the parameters are proper for a neutron star surface. It is to be noticed that the ratio KH/K0 is of the order of (ω/ωH)2 or [(kT/mc2)/(H/Hq]2. One therefore can conclude that the presence of a magnetic field itself assures the beaming of radiation along the field lines.

scholarly journals Effect of Photon Rocket in X-ray Binaries

2000 ◽  
Vol 177 ◽  
pp. 653-654
Author(s):  
V. D. Pal’shin ◽  
A. I. Tsygan
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Gravitational Attraction ◽  
Dipolar Field ◽  
X Ray ◽  
The Galaxy ◽  
Star Surface ◽  
X Ray Binaries ◽  
The Magnetic Field

AbstractIt is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.

Acoustic End Effects in Magnetohydrodynamic Submerged Vehicular Propulsors

1992 ◽  
Vol 36 (01) ◽  
pp. 69-76
Author(s):  
John S. Walker ◽  
Gita Talmage ◽  
Samuel H. Brown ◽  
Neal A. Sondergaard
Keyword(s):  
Magnetic Field ◽  
Inertial Force ◽  
Zero Field ◽  
Uniform Field ◽  
Field Region ◽  
Characteristic Ratio ◽  
Fringing Field ◽  
Field Lines ◽  
Channel Configuration ◽  
The Magnetic Field

This paper treats the effects near the ends of the channel on the transmission and reflection of periodic acoustic waves generated at some cross section inside a magnetohydrodynamic (MHD) seawater propulsion system. A region of high uniform magnetic field inside the MHD submerged vehicular propulsor is separated from the essentially zero magnetic field outside the channel by a nonuniform, fringing magnetic field at each end of the channel. The channel configuration chosen here is that of a straight, rectangular duct with electrically insulating top and bottom walls perpendicular to the magnetic field and highly conducting sidewalls parallel to the field. In particular, the mathematical analysis focuses on determining the percentage of the incident wave which is reflected by the fringing-field region back into the uniform-field region and the percentage which is transmitted through the fringing-field region into the zero-field region. The key parameter is the acoustic interaction parameter N, which is the characteristic ratio of the electromagnetic body force opposing motions across magnetic field lines to the inertial "force" in the acoustic wave. Solutions are presented for the fundamental, plane acoustic mode for arbitrary values of Ν and for all acoustic modes for Ν < 1. The amplitudes of the reflected and transmitted waves depend on the wave frequency, the length of the fringing-field region, N, and the type of wave mode. The magnetic field introduces a strong anisotropy with strong damping of modes involving transverse motions across magnetic field lines and with weak damping of modes involving transverse motions along field lines. This is the third in a series of articles on MHD marine propulsion from the David Taylor Research Center MHD propulsion program [Brown et al (1990), Tempelmeyer (1990)].

scholarly journals Cyclotron Line Emission from Accretion onto a Magnetized Neutron Star

1981 ◽  
Vol 93 ◽  
pp. 233-233
Author(s):  
E. E. Salpeter
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Landau Level ◽  
Optical Depth ◽  
Radiative Decay ◽  
Line Emission ◽  
Collisional Excitation ◽  
Magnetic Field Axis ◽  
Cyclotron Line ◽  
The Magnetic Field

For material accreting along the magnetic field axis of a neutron star, electrons are quantized into Landau orbits. Collisional excitation of the first excited Landau level, followed by radiative decay, leads to the emission of a cyclotron line. The expected line is broad, because the optical depth is large, and its shape is difficult to calculate. Redshifts due to the recoil of a scattering electron and blueshifts due to scattering from the infalling accretion column are being calculated by I. Wasserman, as well as the proton stopping length in the presence of a magnetic field.

scholarly journals On the Submergence and Reemergence of Magnetic Fields in Young Supernovae

2017 ◽  
Vol 45 ◽  
pp. 1760051
Author(s):  
Cristian G. Bernal
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Diffusion Processes ◽  
Flash Method ◽  
Core Collapse ◽  
Reverse Shock ◽  
Magnetic Diffusion ◽  
Mhd Simulations ◽  
Star Surface ◽  
The Magnetic Field

In this work I present numerical magnetohydrodynamic (MHD) simulations of the early dynamics around newly born neutrons stars using the AMR Flash method. When the core-collapse supernovae occurs a reverse shock is formed allowing strong accretion onto the neutron star surface (hypercritical phase). In such regime large amounts of matter are deposited on the neutron star surface, submerging the magnetic field in the new crust. When the hypercritical regime is over, the magnetic field can suffer a reemergence episode due to magnetic diffusion processes, allowing the delayed switch-on of pulsars.

scholarly journals Anomalous diffusion across a tera-Gauss magnetic field in accreting neutron stars

2020 ◽  
Vol 86 (6) ◽  
Author(s):  
Russell M. Kulsrud ◽  
Rashid Sunyaev
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Flux Distribution ◽  
Polar Regions ◽  
X Ray ◽  
Princeton University ◽  
Neutron Star Mass ◽  
Field Lines ◽  
Strong Ideal ◽  
The Magnetic Field

When mass falls on the polar regions of a neutron star in a binary X-ray source system, it tends to spread out over the entire surface. A long-standing question in research on this problem is: will the mass be anchored on the magnetic field lines and drag the field with it or is there a special mechanism that allows the mass to slip through the magnetic field lines, leading to much less distortion? As the amount of mass falling on the neutron star can actually be comparable with the neutron star mass, the question of which alternative holds is very important. We suggest an efficient mechanism that will allow the mass to slip through the lines. The mechanism is based on a strong ideal Schwarzschild (Structure and Evolution of the Stars. Princeton University Press, 1958) instability. As the instability itself is ideal, it cannot directly force the mass to slip though the lines. However, it can create a cascade of eddies whose scale extends down to a resistive scale, at the same time mixing the field lines up without breaking them. On this scale the mass can cross the lines. This instability is efficient enough that it can produce a mass flow in the plasma without growing to a large amplitude but saturates at a small one. The instability determines the mass per flux distribution of the accumulated material on different lines so that the equilibrium is marginal to the instability on every line. This makes the equilibrium unique. Thus, as the extra mass on the neutron star grows, the state of the outer shell proceeds through a sequence of unique critically unstable equilibria. In an appendix, an attempt is made to track the critical equilibria over long times.

scholarly journals Polar Gap Properties for Neutron StarWithin Light Cylinder Limits

2008 ◽  
Vol 5 (4) ◽  
pp. 612-618
Author(s):  
Baghdad Science Journal
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Potential Drop ◽  
Stellar Surface ◽  
Physical Motion ◽  
Condensed Layer ◽  
Polar Gap ◽  
Field Lines ◽  
The Magnetic Field

The huge magnetic fields of neutron star cause the nuclei of the stellar surface to form a tightly bound condensed layer. In this research some characteristics of polar gap and magnetosphere enclosed the star according to Sturrock Model were illustrated, positrons move out along the open field lines, and electrons flow to the stellar surface as in the related to Sturrock model. The magnetic field within polar gap areas, which is defined by the Irvin Radius (RL) decreases due to the expansion of the polar, resulting from the physical motion of the accreted material. The values of height gap at different distances from the star were estimated. The obtained results improve the most energetic positrons those with E? Emax radiate away their energy in a distances re = 104m above the polar gap while less energetic positrons produced at much greater distances re =108m. The potential drop across the polar gap is obtained using a well defined adopted formula, it is found that the potential drop across the polar gap grows like (h2), when h « rp

scholarly journals Accretion and magnetic field submergence in neutron star surface

2008 ◽  
Vol 4 (S259) ◽  
pp. 135-136
Author(s):  
C. Giovanny Bernal ◽  
Dany Page ◽  
William H. Lee
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Neutron Star Crust ◽  
Star Surface ◽  
The Magnetic Field

AbstractWe study the effects of hypercritical accretion onto a neutron star surface. The magnetic field submergence in the neutron star crust and the possible rediffusion is investigated.

scholarly journals Location of the Core and Conal Emission Regions in PSR 0329+54

1992 ◽  
Vol 128 ◽  
pp. 180-182
Author(s):  
J. A. Gil ◽  
M. V. Popov
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Correlation Analysis ◽  
Cross Correlation ◽  
Strongly Correlated ◽  
Pulse Profile ◽  
The Core ◽  
Cross Correlation Analysis ◽  
Field Lines ◽  
Star Surface

AbstractWe discuss the cross-correlation analysis of single pulses in the emission of PSR 0329+54 observed simultaneously at 102.5 and 1700 MHz. We have found that the observed correlations between the two frequencies are consistent with the model in which the subpulses in single pulses correspond to plasma excitations flowing from the neutron-star surface along dipolar magnetic field lines. The peaks of strongly correlated subpulses at the two frequencies correspond to the same field line at two different emission radii. We have found that the core (central) and the conal (outer) components of the pulse profile of PSR 0329+54 originate at the same distance from the neutron star.

scholarly journals Magnetic nulls in interacting dipolar fields

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Todd Elder ◽  
Allen H. Boozer
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Magnetic Flux Tube ◽  
Electron Inertia ◽  
Characteristic Spatial Scale ◽  
Field Lines ◽  
Dipolar Fields ◽  
Time Required ◽  
Magnetic Null ◽  
The Magnetic Field

The prominence of nulls in reconnection theory is due to the expected singular current density and the indeterminacy of field lines at a magnetic null. Electron inertia changes the implications of both features. Magnetic field lines are distinguishable only when their distance of closest approach exceeds a distance $\varDelta _d$ . Electron inertia ensures $\varDelta _d\gtrsim c/\omega _{pe}$ . The lines that lie within a magnetic flux tube of radius $\varDelta _d$ at the place where the field strength $B$ is strongest are fundamentally indistinguishable. If the tube, somewhere along its length, encloses a point where $B=0$ vanishes, then distinguishable lines come no closer to the null than $\approx (a^2c/\omega _{pe})^{1/3}$ , where $a$ is a characteristic spatial scale of the magnetic field. The behaviour of the magnetic field lines in the presence of nulls is studied for a dipole embedded in a spatially constant magnetic field. In addition to the implications of distinguishability, a constraint on the current density at a null is obtained, and the time required for thin current sheets to arise is derived.

Magnetic Field Spectroheliograms from the San Fernando Observatory

1971 ◽  
Vol 43 ◽  
pp. 329-339 ◽  
Author(s):  
Dale Vrabec
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spiral Structure ◽  
Longitudinal Component ◽  
Solar Telescope ◽  
Solar Magnetic Fields ◽  
San Fernando ◽  
Field Lines ◽  
The Magnetic Field ◽  
Field Network

Zeeman spectroheliograms of photospheric magnetic fields (longitudinal component) in the CaI 6102.7 Å line are being obtained with the new 61-cm vacuum solar telescope and spectroheliograph, using the Leighton technique. The structure of the magnetic field network appears identical to the bright photospheric network visible in the cores of many Fraunhofer lines and in CN spectroheliograms, with the exception that polarities are distinguished. This supports the evolving concept that solar magnetic fields outside of sunspots exist in small concentrations of essentially vertically oriented field, roughly clumped to form a network imbedded in the otherwise field-free photosphere. A timelapse spectroheliogram movie sequence spanning 6 hr revealed changes in the magnetic fields, including a systematic outward streaming of small magnetic knots of both polarities within annular areas surrounding several sunspots. The photospheric magnetic fields and a series of filtergrams taken at various wavelengths in the Hα profile starting in the far wing are intercompared in an effort to demonstrate that the dark strands of arch filament systems (AFS) and fibrils map magnetic field lines in the chromosphere. An example of an active region in which the magnetic fields assume a distinct spiral structure is presented.

Sign in / Sign up

Export Citation Format

Share Document