Pulsar twinkling and relativity

Grenier, I. A.; Harding, A. K.

doi:10.1063/1.2399635

Cited by 12 publications

(14 citation statements)

References 38 publications

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“…The conventional wisdom is that the pulsar activity is associated with relativistic plasma flows along the open magnetic field lines. According to the commonly accepted picture, the polar cap cascade produces electron-positron pairs (see, e.g., reviews by Grenier and Harding (2006); Arons (2007) and references therein), which stream along the open magnetic field lines with relativistic velocities. The pulsar radio emission is believed to be generated in this outflow.…”

Section: Introductionmentioning

confidence: 99%

Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

Lyubarsky

2012

Astrophys Space Sci

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The subpulse modulation of pulsar radio emission goes to prove that the plasma flow in the open field line tube breaks into isolated narrow streams. I propose a model which attributes formation of streams to the process of the electric current adjustment in the magnetosphere. A mismatch between the magnetospheric current distribution and the current injected by the polar cap accelerator gives rise to reverse plasma flows in the magnetosphere. The reverse flow shields the electric field in the polar gap and thus shuts up the plasma production process. I assume that a circulating system of streams is formed such that the upward streams are produced in narrow gaps separated by downward streams. The electric drift is small in this model because the potential drop in narrow gaps is small. The gaps have to drift because by the time a downward stream reaches the star surface and shields the electric field, the corresponding gap has to shift. The transverse size of the streams is determined by the condition that the potential drop in the gaps is sufficient for the pair production. This yields the radius of the stream roughly 10% of the polar cap radius, which makes it possible to fit in the observed morphological features such as the "carousel" with 10-20 subbeams and the system of the core -two nested cone beams.

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Section: Introductionmentioning

confidence: 99%

Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

Lyubarsky

2012

Astrophys Space Sci

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“…The fact that models have been able to explain existing observations fairly well strengthens the need for better observations. As an example, Grenier and Harding [5] summarize results showing that polar cap, slot gap, and outer gap models are capable of explaining, at least to first order, the double-pulse results for the Vela gamma-ray pulsar, given appropriate reasonable assumptions about the pulsar.…”

Section: Challenges and Opportunitiesmentioning

confidence: 99%

Gamma-Ray Pulsar Studies with GLAST

Thompson¹

2008

AIP Conference Proceedings

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Abstract. Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies. GAMMA-RAY PULSARS -INTRODUCTIONBalloon and small satellite observations revealed gamma radiation from the Crab (e.g.[1]) and Vela [2] pulsars in the 1970's, becoming early examples of multiwavelength pulsar studies. The number of gamma-ray pulsars grew to at least seven during the Compton Gamma Ray Observatory (CGRO) mission in the 1990's (for a summary, see [3]). These high-energy photons are produced by primary interactions of the energetic particles accelerated in the pulsar magnetosphere. Their potential for studying some basic interaction processes was one stimulus for the development of pulsar models that included gamma rays as a characteristic. With the recent launch of AGILE and the upcoming launch of GLAST, the gamma-ray window on pulsars offers new promise. CHALLENGES AND OPPORTUNITIESAny satellite observations of pulsars present difficulties not found with ground-based observatories. Satellites move rapidly. Clocks on satellites, particularly before the advent of GPS, require careful monitoring and calibration. Data streams are subject to transmission errors, as well as human errors in design and implementation. Making corrections to a system in orbit is often non-trivial. For gamma-ray telescopes, the challenges are compounded by the low detection rate. Even the brightest pulsars produce high-energy gamma rays separated by many pulse periods. A weak pulsar like PSR B1055−52 yielded only 3 detected photons per day when in the field of view of EGRET on the Compton Observatory. During one day the pulsar rotates more then 400,000 times. Gathering statistics required adding data from many observations, often spaced months or even years apart.The sparse nature of gamma-ray pulsar data has made the field highly dependent on timing information from other wavelengths, primarily radio. The radio astronomy community has been highly supportive of the opposite end of the spectrum. The GLAST team greatly appreciates the help of radio astronomers at Arecibo, GBT, Jodrell Bank, Nançay, Parkes, and other telescopes, as ...

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“…The intensity spectrum of cosmic rays extends over more than ten orders of magnitude in energy with a surprisingly smooth spectrum I(E) ∼ E −2.7... 3.0 (adapted from [4]). …”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

Particle acceleration in cosmic sites

Diehl¹

2009

Eur. Phys. J. D

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Abstract. Particles are accelerated in cosmic sites probably under conditions very different from those at terrestrial particle accelerator laboratories. Nevertheless, specific experiments which explore plasma conditions and stimulate particle acceleration carry significant potential to illuminate some aspects of the cosmic particle acceleration process. Here we summarize our understanding of cosmic particle acceleration, as derived from observations of the properties of cosmic ray particles, and through astronomical signatures caused by these near their sources or throughout their journey in interstellar space. We discuss the candidate-source object variety, and what has been learned about their particle-acceleration characteristics. We conclude identifying open issues as they are discussed among astrophysicists. -The cosmic ray differential intensity spectrum across energies from 10 10 eV to 10 21 eV reveals a rather smooth power-law spectrum. Two kinks occur at the "knee" ( 10 15 eV) and at the "ankle" ( 3 × 10 18 eV). It is unclear if these kinks are related to boundaries between different dominating sources, or rather related to characteristics of cosmic-ray propagation. Currently we believe that galactic sources dominate up to 10 17 eV or even above, and the extragalactic origin of cosmic rays at highest energies merges rather smoothly with galactic contributions throughout the 10 15 -10 18 eV range. Pulsars and supernova remnants are among the prime candidates for galactic cosmic-ray production, while nuclei of active galaxies are considered best candidates to produce ultrahigh-energy cosmic rays of extragalactic origin. The acceleration processes are probably related to shocks formed when matter is ejected into surrounding space from energetic sources such as supernova explosions or matter accreting onto black holes. Details of shock acceleration are complex, as relativistic particles modify the structure of the shock, and simple approximations or perturbation calculations are unsatisfactory. This is where laboratory plasma experiments are expected to contribute, to enlighten the non-linear processes which occur under such conditions. PACS. 96.40 Cosmic rays -95.30 Astrophysical plasma

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Pulsar twinkling and relativity

Cited by 12 publications

References 38 publications

Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

Adjustment of the electric current in pulsar magnetospheres and origin of subpulse modulation

Gamma-Ray Pulsar Studies with GLAST

Particle acceleration in cosmic sites

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