Relativistic Plasma Emission and Pulsar Radio Emission: A Critique

Melrose, D. B.; Gedalin, M.

doi:10.1086/307539

Cited by 104 publications

(141 citation statements)

References 42 publications

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“…The relativistic case gives a much lower cutoff frequency, well below 100 MHz (Melrose & Gedalin 1999;Melrose 2000). Thus, despite the low frequencies involved the interplay between GR and plasma effects in pulsars may potentially be within observable ranges (Popov et al 2006;Malov & Malofeev 2010;Stappers et al 2011).…”

Section: Discussionmentioning

confidence: 99%

Frequency-dependent effects of gravitational lensing within plasma

Rogers

2015

Monthly Notices of the Royal Astronomical Society

131

120

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The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions N ∝ 1/r h with h ≥ 0 in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii, and angular momentum for general h. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density h = 0. We study the behaviour for general h and show that when h = 2 the plasma term acts like an additional contribution to the angular momentum of the passing ray. When h = 3 the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star.

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Section: Discussionmentioning

confidence: 99%

Frequency-dependent effects of gravitational lensing within plasma

Rogers

2015

Monthly Notices of the Royal Astronomical Society

131

120

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“…For a dipole magnetic field, both B and n GJ decrease as 1/R 3 where R is the radial distance. This mode crosses the light line to become subluminal at ω co = 2 γ ω p Melrose & Gedalin 1999). Note that ω co can be much higher than the observed lowest radio frequency unless γ is small or the relevant region is near the LC (Melrose & Gedalin 1999).…”

Section: Wave Modesmentioning

confidence: 83%

“…This mode crosses the light line to become subluminal at ω co = 2 γ ω p Melrose & Gedalin 1999). Note that ω co can be much higher than the observed lowest radio frequency unless γ is small or the relevant region is near the LC (Melrose & Gedalin 1999). The L-O mode can be generated in the superluminal frequency region (above the cutoff frequency ω c ) through nonlinear processes.…”

Section: Wave Modesmentioning

confidence: 91%

“…review by Melrose 2000).Although various emission models have been proposed, none of them has been widely accepted as a successful model that can account for most observations (e.g. Melrose & Gedalin 1999;Melrose 2000). The most important information we have from observations on the radio emission includes the rapid variability of individual pulses (Manchester & Taylor 1977), the integrated pulse profiles which have very stable shapes but vary from pulsar to pulsar (Lyne & Manchester 1988), and the unique polarisation features such as highly linear polarisation and a large component of circular polarisation (Gould & Lyne 1998;Han, Manchester, Xu, & Qiao 1998).…”

Section: Introductionmentioning

confidence: 99%

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Propagation Effects on Pulsar Radio Emission

Luo

2001

Publ. – Astron. Soc. Aust

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Propagation effects on radio emission within the pulsar magnetosphere are discussed. Widely accepted pulsar models assume that a pulsar magnetosphere is populated with relativistic pair plasmas produced through electron–positron cascades by accelerated primary particles above the polar cap. Any radio emission produced well inside the light cylinder (the radius at which the rotation speed equals c) must propagate through the magnetospheric plasma and be subject to plasma dispersion effects such as refraction and absorption. The observed pulse profiles should contain some features that reflect the influence of the intervening plasma. I discuss particularly the absorption effect due to cyclotron resonance and its possible observational consequences.

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“…Oblique (L-O mode) waves have phase speed < c only for a tiny range of angles about () == O. The dispersion curves in the rest frame are plotted in Figure 2 for a small value of (,); beam-driven growth of L-O mode waves is possible only for sufficiently small angles, f) « 1/(,), for which the dispersion curve extends into the region above the line z-2 == 1 in the Figure. These features lead to several unresolved problems (Melrose & Gedalin 1999). First, the frequency of the beam-driven waves (Doppler boosted to the pulsar frame) seems too high to account for all pulsar emission.…”

Section: Radio Emission Mechanismsmentioning

confidence: 99%