分类： 天文学 >> 天文学 提交时间： 2025-07-09
摘要： Five decades after the discovery of radio pulsars, main stream theories based on polar cap still suffer from difficulties in both self-consistency and confrontation with observations[1]. Increasing observation of individual subpulses of pulsars, i.e., high brightness temperature, highly polarized, and narrowband nanoshots of the Crab pulsar[2, 3] indicate that they relate with basic emission elements in a pulse window. Moreover, high degree of circular polarization, and rapid orthogonal jump in the position angle of linear polarization are observed in micropulses of both pulsars and Fast Radio Bursts (FRBs)[3–6], which further requires that such a small element of emission has a rapid variable conal-core pattern rather than a simple bunch of high energy density widely accepted. These are both unprecedented challenges and chances to understand the origin of pulsar coherent emission. This paper confronts with those difficulties by a simple model of alternative emission site and mechanism, in which pulsar wind is launched from open field line region and the coherent emission is triggered by a forced magnetic reconnection occurring at the tip of last closed field line near the light cylinder. The high energy density at such a tiny reconnection site automatically invokes Alfven waves, creates electron-positron pair, and accelerates them into relativistic speed. The resultant particle-wave interaction gives rise to coherent bunches inborn a conal-core structure responsible for observations on pulsars, magnetars and FRBs. For the first time, puzzles on coherency, polarization, correlation of coherent emission with wind, and energy budget of pulsars, magnetars, and FRBs are interpreted by a unified model.
分类： 天文学 >> 天体物理学 提交时间： 2023-12-04
摘要： The pulsar radio emission mechanism remains an enigma over half a century.A successful radiation process requires not only to explain the coherency and high degree of polarization of the emission, but alsomicrostructures, characteristic frequency of emission, and the death line problem, etc. These issues challenge both the long standing cap models and recent models of magnetic reconnection assuming stationary magnetosphere of a pulsar.This article proposes a radio emission through global-local interaction of pulsar magnetosphere. The centrifugal force at the light cylinder leads to the concentration of both field lines and plasma in an equatorial layer much less than that of a pulsar magnetosphere.The resultant magnetic reconnection with chain of plasmoids interprets not only the above problems in a simple and unified way, but also Rotating Radio Transients (RRATs) and Fast Radio Bursts (FRBs).
分类： 天文学 >> 天体物理学 提交时间： 2023-07-29
摘要： The pulsar radio emission mechanism remains an enigma since its discovery in 1967. The critical issue of origin of coherent emission is usually investigated separately from the micro-structure of individual pulses and characteristic emission frequency of pulsars... In this letter, these issues are interpreted in an unified scenario. The pulsar spin piles up magnetic field at the apex of last closed field line triggering magnetic reconnection. The resultant Alfven wave interacts with open field lines giving rise to coherent maser curvature and cyclotron emission. Such a scenario of coherent emission not only imposes new limit to emission site, nanoburst, and characteristic frequency, but also affects polarization and pair production required in maintaining a marginal stable circuit in radio emission of pulsars.
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