scholarly journals Pulsar radio emission mechanisms: a critique

2020 ◽  
Vol 500 (4) ◽  
pp. 4530-4548
Author(s):  
D B Melrose ◽  
M Z Rafat ◽  
A Mastrano
Keyword(s):  
Radio Emission ◽  
Gaussian Distribution ◽  
Rest Frame ◽  
Particle Distribution ◽  
Lorentz Factor ◽  
Relativistic Case ◽  
Pulsar Radio ◽  
Kinetic Instability ◽  
Wave Properties ◽  
Pulsar Radio Emission

ABSTRACT We consider critically the three most widely favoured pulsar radio emission mechanisms: coherent curvature emission (CCE), beam-driven relativistic plasma emission (RPE), and anomalous Doppler emission (ADE). We assume that the pulsar plasma is 1D, streaming outwards with a bulk Lorentz factor γs ≫ 〈γ〉 − 1 ≳ 1, where 〈γ〉 is the intrinsic spread in the rest frame of the plasma. We argue that the formation of beams in a multicloud model is ineffective in the intrinsically relativistic case for plausible parameters because the overtaking takes too long. We argue that the default choice for the particle distribution in the rest frame is a Jüttner distribution and that relativistic streaming should be included by applying a Lorentz transformation to the rest-frame distribution, rather than the widely assumed relativistically streaming Gaussian distribution. We find that beam-driven wave growth is severely restricted by (a) the wave properties in pulsar plasma, (b) a separation condition between beam and background, and (c) the inhomogeneity of the plasma in the pulsar frame. The growth rate for the kinetic instability is much smaller and the bandwidth of the growing waves is much larger for a Jüttner distribution than for a relativistically streaming Gaussian distribution. No reactive instability occurs at all for a Jüttner distribution. We conclude that none of CCE, RPE, and ADE is tenable as the generic pulsar radio emission mechanism for ‘plausible’ assumptions about the pulsar plasma.

scholarly journals A rotation-driven pulsar radio emission mechanism

2020 ◽  
Vol 500 (4) ◽  
pp. 4549-4559
Author(s):  
D B Melrose ◽  
M Z Rafat ◽  
A Mastrano
Keyword(s):  
Radio Emission ◽  
Rest Frame ◽  
Radial Distance ◽  
Lorentz Factor ◽  
Emission Mechanism ◽  
Pulsar Radio ◽  
Specific Frequency ◽  
The Mean ◽  
Pulsar Radio Emission ◽  
Streaming Motion

ABSTRACT We propose and discuss an alternative pulsar radio emission mechanism that relies on rotation-driven plasma oscillations, rather than on a beam-driven instability, and suggest that it may be the generic radio emission mechanism for pulsars. We identify these oscillations as superluminal longitudinal waves in the pulsar plasma and point out that these waves can escape directly in the O mode. We argue that the frequency of the oscillations is ω0 ≈ ωp(2〈γ〉)1/2/γs, where γs is the Lorentz factor of bulk streaming motion and 〈γ〉 is the mean Lorentz factor in the rest frame of the plasma. The dependence of the plasma frequency ωp on radial distance implies a specific frequency-to-radius mapping, ω0∝r−3/2. Escape of the energy in these oscillations is possible if they are generated in overdense, field-aligned regions that we call fibres; the wave energy is initially refracted into underdense regions between the fibres, which act as ducts. Some implications of the model for the interpretation of pulsar radio emission are discussed.

scholarly journals Coherent radio emission from pulsars

1992 ◽  
Vol 341 (1660) ◽  
pp. 105-115 ◽  
Keyword(s):  
Radio Emission ◽  
Linear Acceleration ◽  
Wave Mode ◽  
High Brightness ◽  
Pulsar Radio ◽  
Pulsar Radiation ◽  
Indirect Emission ◽  
Kinetic Instability ◽  
Beam Instabilities ◽  
Pulsar Radio Emission

The high brightness temperature of pulsar radiation requires that the emission process be coherent. There are three possibilities in principle: emission by bunches; reactive instability, due to an intrinsically growing wave mode; and kinetic instability, which is maser action. The emission may be direct or indirect, depending on whether the radiation can escape to infinity through the pulsar magnetosphere, or must first be converted into another wave mode. Early models favoured either direct curvature emission by bunches or indirect emission due to a reactive beam instability, but before about 1980 it was realized that there are serious problems with both mechanisms. There are strong physical arguments against emission by bunches being viable, and the first detailed analysis suggested that the seemingly plausible alternative of maser curvature emission is impossible. Also the growth rates for beam instabilities were found too small to allow waves to grow effectively. Alternative emission mechanisms, including cyclotron and linear acceleration emissions, and variants on the existing mechanisms have been considered. In this paper the suggested emission mechanisms are reviewed from a plasma-physical viewpoint, and they are then compared to see how they might fit into a phenomenological model for pulsar radio emission.

scholarly journals Characteristics of Pulsar Radio Emission at Single-pulse Resolution

2000 ◽  
Vol 177 ◽  
pp. 149-154
Author(s):  
Avinash A. Deshpande
Keyword(s):  
Radio Emission ◽  
Weighted Average ◽  
Single Pulse ◽  
Position Angle ◽  
Complex Nature ◽  
Stable States ◽  
Pulsar Radio ◽  
Emission Profile ◽  
Secondary State ◽  
Pulsar Radio Emission

Pulsar radio emission shows remarkably rich, but complex behavior in both intensity and polarization when considered on a pulse-to-pulse basis. A large number of pulses, when averaged together, tend to approach & define stable shapes that can be considered as distinct signatures of different pulsars. Such average profiles have shapes ranging from that describable as a simple one-component profile to those suggesting as many as 9 components. The components are understood as resulting from an average of many, often narrower, intities — the subpulses —that appear within the longitude range of a given component. The pulse components are thusformedand represent statistically an intensity-weighted average pattern of the radiation received as a function of longitude. The profile mode changes recognized in many pulsars suggest that the emission profile of a given pulsar may have two quasi-stable states, with one (primary) state more probable/brighter than the other (secondary) state. There are also (often associated) polarization modes that represent polarization states that are orthogonal to each other. The complex nature of orthogonaljumpsobserved in polarization position-angle sweeps may be attributable to possible superposition of two profile/polarization modes with orthogonal polarizations.

scholarly journals Parameters of microstructure and noiselike intensity fluctuation in pulsar radio emission measured with submicrosecond time resolution provided by the S2 VLBI recording/playback system

2000 ◽  
Vol 177 ◽  
pp. 179-180 ◽  
Author(s):  
M.V. Popov ◽  
V.I. Kondrat’ev ◽  
V.I. Altunin ◽  
N. Bartel ◽  
W. Cannon ◽  
...  
Keyword(s):  
Radio Emission ◽  
Data Acquisition ◽  
Radio Telescope ◽  
Time Resolution ◽  
Intensity Fluctuation ◽  
Data Acquisition System ◽  
Acquisition System ◽  
Pulsar Radio ◽  
Removal Technique ◽  
Pulsar Radio Emission

AbstractThree bright pulsars (B0950+08, B1133+16, and B1929+10) were observed with the 70-m radio telescope in Tidbinbilla at a frequency of 1650 MHz using the S2 Data Acquisition System which provided continuous recording of pulsar signals in two conjugate bands of B=16 MHz each. Parameters of microstructure have been analyzed using the predetection dispersion removal technique.

scholarly journals Evolution of Multipolar Magnetic Fields in Isolated Neutron Stars and its effect on Pulsar Radio Emission

2000 ◽  
Vol 177 ◽  
pp. 265-266
Author(s):  
D. Mitra ◽  
S. Konar ◽  
D. Bhattacharya ◽  
A. V. Hoensbroech ◽  
J. H. Seiradakis ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Neutron Stars ◽  
Pulse Shape ◽  
Position Angle ◽  
Emission Region ◽  
Pulsar Radio ◽  
Significant Frequency ◽  
The Magnetic Field ◽  
Pulsar Radio Emission

AbstractThe evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. Lower orders (≤ 25) of multipole are seen to evolve in a manner similar to the dipole suggesting little or no evolution of the expected pulse shape. We also study the multifrequency polarization position angle traverse of PSR B0329+54 and find a significant frequency dependence above 2.7 GHz. We interpret this as an evidence of strong multipolar magnetic field present in the radio emission region.

scholarly journals Mechanism of pulsar radio emission

2002 ◽  
Vol 337 (2) ◽  
pp. 422-430 ◽  
Author(s):  
M. Gedalin ◽  
E. Gruman ◽  
D. B. Melrose
Keyword(s):  
Radio Emission ◽  
Pulsar Radio ◽  
Pulsar Radio Emission

Observations of pulsar radio emission. III - Stability of integrated profiles

1975 ◽  
Vol 198 ◽  
pp. 661 ◽  
Author(s):  
D. J. Helfand ◽  
R. N. Manchester ◽  
J. H. Taylor
Keyword(s):  
Radio Emission ◽  
Pulsar Radio ◽  
Pulsar Radio Emission
Sign in / Sign up

Export Citation Format

Share Document