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： 2024-01-16
摘要： The pulsar radio emission mechanism remains an enigma since over half a century. A radiation process requires not only to explain the coherency and high degree of polarization of the emission, but also nanobursts, characteristic frequency of emission, and problems like death line, which can#2;not be well understood in the context of long standing cap models and recent models of magnetic reconnection. This article proposes a dynamo process in pulsar magnetosphere. Through centrifu#2;gal force the last closed magnetic field lines can be amplified to a critical value of, BT 104T, which triggers magnetic reconnection responsible for the instability required in coherent curvature radiation, so that a number of problems can be interpreted. The time scale of magnetic field pile up and relaxation can be short or long for young or old pulsars respectively, which naturally account for the diverse intermittencies exhibited in pulsars and FRBs.
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