scholarly journals Visibility of Pulsar Emission: Motion of the Visible Point

2014 ◽  
Vol 31 ◽  
Author(s):  
R. Yuen ◽  
D. B. Melrose
Keyword(s):  
Field Line ◽  
Vector Model ◽  
Line Of Sight ◽  
Dipolar Field ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Wide Range ◽  
Recent Claim ◽  
Rotational Phase ◽  
Pulsar Radio Emission

AbstractA standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara, 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, ψ, defining a trajectory on a sphere of radius r. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al., 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of ψ. The RVM tends to underestimate the range of ψ over which emission is visible. We suggest that the geometry alone strongly favors the visible pulsar radio being emitted at a heights more than ten percent of the light-cylinder distance, where our neglect of retardation effects becomes significant.

scholarly journals Pulsar radio beams and emission altitudes

1996 ◽  
Vol 160 ◽  
pp. 287-288
Author(s):  
Jaroslaw Kijak ◽  
Janusz A. Gil
Keyword(s):  
Emission Region ◽  
Intensity Level ◽  
Pulse Profile ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Pulsar Radiation ◽  
Measured Profile ◽  
Field Lines ◽  
The Relationship ◽  
Pulsar Radio Emission

We verify the relationship proposed by Kijak and Gil (1996) for the pulsar radio emission altitudes(see also Eq.3 in Gil & Krawczyk, 1996), using the pulse-profile Effelsberg raw data at 1.41 GHz. We measured profile pulse-widths at the lowest intensity level corresponding to 0.01% of the maximum intensity (Fig. 1b), using the polarlog-scale technique (Hankins and Fowler, 1986). We calculated opening angles (Fig. 1a) and emission altitudes (Fig. 1c) assuming that:i) pulsar radiation is narrow-band with radius-to-frequency mapping operating in the emission region,ii) pulsar emission is beamed tangentially to the dipolar magnetic field lines,iii) the extreme profile wings originate near or at the last open field lines.

scholarly journals Single Pulses and the Plasma-physical Processes of Pulsar Radio Emission

2017 ◽  
Vol 13 (S337) ◽  
pp. 73-78
Author(s):  
Joanna M. Rankin
Keyword(s):  
Radio Emission ◽  
Pulse Sequences ◽  
Single Pulse ◽  
Physical Processes ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Cone Model ◽  
Chart Recorder ◽  
Polarization Characteristics ◽  
Pulsar Radio Emission

AbstractPulsars were discovered on the basis of their individual pulses, first by Jocelyn Bell and then by many others. This was chart-recorder science as computers were not yet in routine use. Single pulses carry direct information about the emission process as revealed in the detailed properties of their polarization characteristics. Early analyses of single pulses proved so dizzyingly complex that attention shifted to study of average profiles. This is turn led to models of pulsar emission beams—in particular the core/double-cone model—which now provides a foundation for understanding single-pulse sequences. We mention some of the 21stC single-pulse surveys and conclude with a brief discussion of our own recent analyses leading to the identification of the pulsar radio-emission mechanism of both slow and millsecond pulsars.

scholarly journals Search for a Correlation Between Radio Giant Pulses and VHE Photons of the Crab Pulsar

10.14311/1472 ◽  
2011 ◽  
Vol 51 (6) ◽  
Author(s):  
N. Lewandowska ◽  
D. Elsäesser ◽  
K. Mannheim
Keyword(s):  
Radio Emission ◽  
Special Form ◽  
Electromagnetic Spectrum ◽  
Crab Pulsar ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Giant Pulses ◽  
Pulse Structure ◽  
Unique Source ◽  
Pulsar Radio Emission

The Crab pulsar is a unique source of pulsar radio emission. Its regular pulse structure is visible over the entire electromagnetic spectrum from radio to GeV ranges. Among the regular pulses, radio giant pulses (GPs) are known as a special form of pulsar radio emission. Although the Crab pulsar was discovered by its GPs, their origin and emission mechanisms are currently not understood. Within the framework of this report we give a review on radio GPs and present a new idea on how to examine the characteristics of this as yet not understood kind of pulsar emission.

Pulsar scintillation as a physical tool

1992 ◽  
Vol 341 (1660) ◽  
pp. 167-176 ◽  
Keyword(s):  
Spatial Coherence ◽  
Line Of Sight ◽  
Interstellar Gas ◽  
Pulsar Emission ◽  
Pulsar Radiation ◽  
Wide Range ◽  
Random Modulation ◽  
Radio Frequency Spectrum ◽  
The Galaxy ◽  
Diffraction Patterns

The interstellar gas contains irregularities of electron density having a wide range of physical scales. Pulsar radiation propagating through this inhomogeneous medium suffers a random modulation of phase which causes the received intensity to scintillate on a variety of timescales. Observations of the radio frequency spectrum and temporal variation of scintillation give information on the form of the irregularity spectrum and the distribution of density structure across the Galaxy. The high spatial coherence of pulsar radiation leads to the formation of extremely fine-scale diffraction patterns which also provide information on the motion of sources across the line of sight and the size of pulsar emission regions. Some uses of scintillation as a means of probing the interstellar gas and elucidating the physical properties of pulsars will be discussed.

scholarly journals Pulsar Studies at High Radio Frequencies

2000 ◽  
Vol 177 ◽  
pp. 205-210 ◽  
Author(s):  
Richard Wielebinski
Keyword(s):  
Radio Sources ◽  
Radio Telescopes ◽  
Frequency Range ◽  
High Luminosity ◽  
Max Planck ◽  
Pulsar Emission ◽  
Millisecond Pulsars ◽  
Pulsar Radio ◽  
Radio Frequencies ◽  
Pulsar Radio Emission

AbstractPulsars were discovered at 81.5 MHz and a lot of the studies of these exciting objects have been made up to the present time at radio frequencies below 1.6 GHz. The reasons for this concentration on the low radio frequency characteristics of pulsars is the fact that the spectra are very steep and that very few radio telescopes exist that are capable of efficient operations at high radio frequencies. The Effelsberg 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie operates regularly up to the frequency of 50 GHz and was used to study pulsars at cm/mm-wavelengths. In the southern skies the Parkes 64-m telescope has been used to study pulsars up to 8.4 GHz. One pulsar has been detected at 87 GHz with the 30-m Pico Veleta telescope of IRAM.The studies of pulsars over the whole frequency range are of great importance because this is necessary for the elucidation of the mechanism that is responsible for the pulsar emission. The high polarization of pulsar radio emission at lower radio frequencies has supported the hypothesis of a coherent emission mechanism, which is required to generate the high luminosity. It has been known for some time that pulsars, unlike other radio sources, have a lower polarization at high radio frequencies. Recently a change of pulsar spectrum, a flattening or possibly an inversion has been observed at the highest radio frequencies. The inversion of the pulsar spectrum seems to coincide with a complete depolarization of some pulsars.Millisecond pulsars are less luminous than normal pulsars. This makes them even more difficult to detect at higher radio frequencies. Recent observations have extended the spectra of ten millisecond pulsars up to 4.85 GHz. The results imply that millisecond pulsars have properties very similar to normal (slow) pulsars, which suggests similar emission mechanisms.

scholarly journals Orthogonal Polarization Modes in Pulsar Radio Emission

2004 ◽  
Vol 218 ◽  
pp. 377-380
Author(s):  
S. A. Petrova
Keyword(s):  
Radio Emission ◽  
Field Line ◽  
Plasma Density ◽  
Orthogonal Polarization ◽  
Pulsar Radio ◽  
Open Field Line ◽  
Exponential Decrease ◽  
Polarization Profiles ◽  
First Time ◽  
Pulsar Radio Emission

General features of polarization transfer in the plasma of pulsar magnetospheres are outlined. A technique of plasma density diagnostics based on observed polarization profiles of radio pulses is developed. For the first time, it appears possible to obtain the profiles of the plasma density across the open field line tube from observations. The multiplicities derived are compatible with those predicted by modern theories of pair cascade and show a perfect exponential decrease towards the tube edge. Implications of the results are briefly discussed.

scholarly journals Polarization sounding of the pulsar magnetosphere

2012 ◽  
Vol 8 (S291) ◽  
pp. 530-532 ◽  
Author(s):  
O. M. Ulyanov ◽  
A. I. Shevtsova ◽  
A. A. Seredkina
Keyword(s):  
Broad Band ◽  
Probe Signal ◽  
Pulsar Magnetosphere ◽  
Free Electrons ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Decameter Wavelength ◽  
Propagation Medium ◽  
Pulsar Radio Emission ◽  
Stratified Model

AbstractThe possibility of a polarization sounding of the pulsar magnetosphere is examined, using intrinsic pulsar emission as a probe signal, for modern radio telescopes operating in the meter and decameter wavelength range. Different models of the pulsar magnetosphere at altitudes higher than a radius of critical polarization are used. The propagation medium besides magnetosphere is described by the stratified model, in which each layer has its own density of free electrons and vector of magnetic induction, as well as the spatial and temporal fluctuation scales of these parameters.The frequency dependence of the polarization parameters of the pulsar radio emission, obtained in the broad band for a selected pulse phase, will enable a sounding deep into the pulsar magnetosphere.

scholarly journals Pulsar polarimetry with the Parkes ultra-wideband receiver

2020 ◽  
Vol 496 (2) ◽  
pp. 1418-1429
Author(s):  
Lucy Oswald ◽  
Aris Karastergiou ◽  
Simon Johnston
Keyword(s):  
Broad Band ◽  
Relativistic Effects ◽  
Position Angle ◽  
Ultra Wideband ◽  
Pulsar Emission ◽  
Height Range ◽  
Pulsar Radio ◽  
First Time ◽  
Pulsar Radio Emission ◽  
Do So

ABSTRACT Pulsar radio emission and its polarization are observed to evolve with frequency. This frequency dependence is key to the emission mechanism and the structure of the radio beam. With the new ultra-wideband receiver (UWL) on the Parkes radio telescope we are able, for the first time, to observe how pulsar profiles evolve over a broad continuous bandwidth of 700–4000 MHz. We describe here a technique for processing broad-band polarimetric observations to establish a meaningful alignment and visualize the data across the band. We apply this to observations of PSRs J1056–6258 and J1359–6038, chosen due to previously unresolved questions about the frequency evolution of their emission. Application of our technique reveals that it is possible to align the polarization position angle (PA) across a broad frequency range when constrained to applying only corrections for dispersion and Faraday rotation to do so. However, this does not correspond to aligned intensity profiles for these two sources. We find that it is possible to convert these misalignments into emission height range estimates that are consistent with published and simulated values, suggesting that they can be attributed to relativistic effects in the magnetosphere. We discuss this work in the context of the radio beam structure and prepare the ground for a wider study of pulsar emission using broad-band polarimetric data.

scholarly journals The Status of Pulsar Emission Theory

2000 ◽  
Vol 177 ◽  
pp. 721-726 ◽  
Author(s):  
D.B. Melrose
Keyword(s):  
Plasma Frequency ◽  
Emission Mechanism ◽  
Number Density ◽  
Langmuir Turbulence ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Testable Prediction ◽  
The Status ◽  
Statistical Sense ◽  
Pulsar Radio Emission

AbstractIt is argued that there is now a preferred pulsar radio emission mechanism, involving beam-driven Langmuir turbulence. A testable prediction is that, at least in a statistical sense, features in the spectra of pulsars should scale with the plasma frequency,υGJ, implied by the Goldreich-Julian number density.

scholarly journals A Ray-Tracing Model of the Vela Magnetosphere

2000 ◽  
Vol 177 ◽  
pp. 437-438
Author(s):  
C. Hirano ◽  
C. R. Gwinn
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Simple Model ◽  
Field Line ◽  
Pulse Profile ◽  
Pulsar Radio ◽  
Vela Pulsar ◽  
Qualitative Characteristics ◽  
Pulsar Radio Emission ◽  
Ray Tracing Model

AbstractIn the relativistic plasma surrounding a pulsar, a subluminal ordinary-mode electromagnetic wave will propagate along a magnetic field line. After some distance, it can break free of the field line and escape the magnetosphere to reach an observer. We apply a simple model of pulsar radio emission based on this scenario to the case of the Vela pulsar and find it reproduces some qualitative characteristics of the observed Vela pulse profile.

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