强磁场对中子星壳层热核反应的影响     

罗志全  彭秋和 《中国天文和天体物理学报》1996,(4)

本文通过考虑强磁场中电子的量子效应，分析了强磁场下电子气体的Fermi能，讨论了磁场对核的屏蔽势和核反应率的影响，进而计算了强磁场对天体物理中几个较重要的热核反应的影响，结果表明，相对于无磁场而言，在较低密度下，足够强的磁场使原子核的屏蔽势显著增加，但在ρ／μe＞10~5molcm~(-3)的密度下，中子星表面存在的强度为10~5～10~9T范围内的磁场对核反应率几乎没有影响。  相似文献   

Dynamics of the solar tachocline – I. An incompressible study     

P. Garaud 《Monthly notices of the Royal Astronomical Society》2002,329(1):1-17

Gough & McIntyre have suggested that the dynamics of the solar tachocline are dominated by the advection–diffusion balance between the differential rotation, a large-scale primordial field and baroclinicly driven meridional motions. This paper presents the first part of a study of the tachocline, in which a model of the rotation profile below the convection zone is constructed along the lines suggested by Gough & McIntyre and solved numerically. In this first part, a reduced model of the tachocline is derived in which the effects of compressibility and energy transport on the system are neglected; the meridional motions are driven instead by Ekman–Hartmann pumping. Through this simplification, the interaction of the fluid flow and the magnetic field can be isolated and is studied through non-linear numerical analysis for various field strengths and diffusivities. It is shown that there exists only a narrow range of magnetic field strengths for which the system can achieve a nearly uniform rotation. The results are discussed with respect to observations and to the limitations of this initial approach. A following paper combines the effects of realistic baroclinic driving and stratification with a model that closely follows the lines of work of Gough & McIntyre.  相似文献   

二维太阳光谱观测方法和技术     

叶式辉 《天文学进展》1997,15(1):36-43

经典的太阳光谱观测是一维的，它有很大的局限性。从５０年代起，天文工作者采用多种方法开展二维太阳光谱观测，已经研制出一系列仪器，建立完整的资料归算程序，取得优良成果。在二维观测资料的基础上，用理论方法推出深度分布，可以得出三维的立体图像，这会成为太阳研究的主要方法之一。  相似文献   

Electric charge and magnetic flux on rotating black holes in a force-free magnetosphere     

Hyun KyuLee  Chul H.Lee  Maurice H. P. M.van Putten 《Monthly notices of the Royal Astronomical Society》2001,324(3):781-784

The electric charge on rotating black holes is calculated to be ∼ BJ in the force-free configuration of Ghosh, with a horizon flux of ∼ BM ². This charge is gravitationally weak for B ∼10¹⁵ G , so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field.  相似文献   

Magnetic flux separation in photospheric convection     

N. O. Weiss  M. R. E. Proctor  D. P. Brownjohn 《Monthly notices of the Royal Astronomical Society》2002,337(1):293-304

Three-dimensional non-linear magnetoconvection in a strongly stratified compressible layer exhibits different patterns as the strength of the imposed magnetic field is reduced. There is a transition from a magnetically dominated regime, with small-scale convection in slender hexagonal cells, to a convectively dominated regime, with clusters of broad rising plumes that confine the magnetic flux to narrow lanes where fields are locally intense. Both patterns can coexist for intermediate field strengths, giving rise to flux separation: clumps of vigorously convecting plumes, from which magnetic flux has been excluded, are segregated from regions with strong fields and small-scale convection. A systematic numerical investigation of these different states shows that flux separation can occur over a significant parameter range and that there is also hysteresis. The results are related to the fine structure of magnetic fields in sunspots and in the quiet Sun.  相似文献   

How Fast Could a Proto-pulsar Rotate?     

Ren-Xin Xu  Hong-Guang Wang  Guo-Jun QiaoDepartment of Astronomy  School of Physics  Peking University  Beijing 《中国天文和天体物理学报》2002,2(6)

According to two estimated relations between the initial period andthe dynamo-generated magnetic dipole field of pulsars, we calculate the statisticaldistributions of pulsar initial periods. It is found that proto-pulsars are very likelyto have rotation periods between 20 ms and 30 ms, and that most of the pulsarsrotate initially at a period ＜ 60 ms. Our result supports the asymmetric neutrinoemission model for pulsar kick.  相似文献   

北京大灰厂试验场重力变化特征及其解释     

孟国杰  张晶  张成强 《大地测量与地球动力学》1996,(3)

介绍了北京大灰厂试验场（简称京西试验场）的概况，对１９９３年３月以来重力重复观测资料进行了处理。计算了各期重力观测精度，结果显示１９９３年３月～１９９５年５月京西试验场存在一定重力变化。采用给定的模型反演了八宝山断层介质的密度变化，认为断层破碎带介质密度的变化可能是引起地表重力变化的主要因素  相似文献   

Harmonic Structures of Gyrosynchrotron Radiation and Cyclotron Maser Instability     

Ai-Hua Zhou  Guang-Li Huang 《中国天文和天体物理学报》2001,1(4):365-371

1 INTRODUCTIONSolar microwave bursts are usually produced by dtherellt radiation mechanisxns: gyroresonance absorption, Coulomb brernsstrahlung of the thermal baCkground plasma, as well asgyrosynchrotron radiation of the nonihermal electrons (Hildebrandt et al. 1998). Meanwhile,cyclotron or synchrotron maser instabilities may be responsible for microwave spaaes, blips, andtype ill bursts (Wu 1985; Huang 1987; Huang et al. 1996; Huang 1998), which are usuajly superposed on the ambient mi…  相似文献   

解决太阳横向磁场方向测定中180°不确定性的一个方法     

汪景琇 《中国天文和天体物理学报》1994,(2)

本文提出了一种解决太阳横向磁场方向测定中１８０°不确定性的方法。该方法首先将Ｇａｒｙ等提出的方法定量化，客观地确定每一点的横场方向；然后由独立的Ｈ＿α观测或磁场演化历史，分析和确定磁力线的拓扑联接性，对客观确定的横场方向做经验修正。对活动区的应用表明，该方法是一个可供选择的解决横场方向不确定性的有效方法。  相似文献   

Torsional oscillations of magnetized relativistic stars     

Neophytos Messios  Demetrios B. Papadopoulos  Nikolaos Stergioulas 《Monthly notices of the Royal Astronomical Society》2001,328(4):1161-1168

Strong magnetic fields in relativistic stars can be a cause of crust fracturing, resulting in the excitation of global torsional oscillations. Such oscillations could become observable in gravitational waves or in high-energy radiation, thus becoming a tool for probing the equation of state of relativistic stars. As the eigenfrequency of torsional oscillation modes is affected by the presence of a strong magnetic field, we study torsional modes in magnetized relativistic stars. We derive the linearized perturbation equations that govern torsional oscillations coupled to the oscillations of a magnetic field, when variations in the metric are neglected (Cowling approximation). The oscillations are described by a single two-dimensional wave equation, which can be solved as a boundary-value problem to obtain eigenfrequencies. We find that, in the non-magnetized case, typical oscillation periods of the fundamental     torsional modes can be nearly a factor of 2 larger for relativistic stars than previously computed in the Newtonian limit. For magnetized stars, we show that the influence of the magnetic field is highly dependent on the assumed magnetic field configuration, and simple estimates obtained previously in the literature cannot be used for identifying normal modes observationally.  相似文献