试论行星磁场强度分布的成因

行星磁场强度的分布具有规律性,中间巨行星的强度值大,两侧类地行星和远日行星的强度值小。在类地行星和远日行星中,也是中间行星磁场强度值大,如地球和海王星。两侧行星磁场强度值小,如金星、火星、天王星和冥王星。水星磁场强度值比金星大是因为水星环较早的从A组星云环中分裂出来所致。行星磁场强度大小分布的规律性与星云环级式分裂、环体物质中聚即铁磁性物质较快中聚的规律性一致。所以,铁磁性物质多少,可能是行星磁场强度大小分布的一个主要原因。     

Influence of Star Formation on Large Scale Structures of Galactic Magnetic Fields

In order to study magnetic field generation in galaxies with active processes such as intensive star formation, supernovae explosions, etc, a model is needed to differentiate between the properties of interstellar medium in different parts of the galactic disk. In this paper we consider galactic dynamo equations with stochastic coefficients where the parameters responsible for dissipation randomly depend on time and spatial coordinates and are distributed around two values corresponding to aweakly heated neutral component and a hot ionized component. Ionized gas is assumed to be concentrated in small regions evenly distributed over the galactic disk plane. The ratio of the total area of such regions to the entire disk plane corresponds to the mean surface star-formation density in the given region of the galactic disk. Unlike in our previous papers, we take into account the dissipation in the disk plane. We have obtained numerical estimates of the exponential growth rate for different numbers of areas containing ionized gas. We show that the influence of the fluctuations on the magnetic field behavior has a threshold nature; intensive star formation leads to the destruction of large scale magnetic field structures.     

Analytical Planetary solution VSOP2000

The analytical planetary solution VSOP2000 determines the planetary perturbations with the help of an iterative method from a solution developed till the third order of the disturbing masses. This solution is from 10 to 100 times more precise than the previous analytical solutions VSOP82 and VSOP87, at the level of some 0.1mas for Mercury, Venus and the Earth and some mas for the other planets over the timespan 1900–2000.With this solution, the relation between the Barycentric Coordinate Time (TCB) and the Geocentric Coordinate Time (TCG) is computed with an accuracy better than 0.1 nanosecond over the interval 1965–2015. We also determined the contribution to the Eulerian angles of the geodetic precession-nutation.     

Variation of Small Scale Magnetic Fields Over a Century using Ca-K Images as Proxy

A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory, Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century. The small scale features are classified into three distinct categories:enhanced network, active network and quiet network. All these features show that their areas vary according to the11 yr solar cycle. The relative amplitude of the Ca-K networ...     

Estimation of Solar Prominence Magnetic Fields Based on the Reconstructed 3D Trajectories of Prominence Knots

We present an estimation of the lower limits of local magnetic field strengths in quiescent, activated, and active (surges) prominences, based on reconstructed three-dimensional (3D) trajectories of individual prominence knots. The 3D trajectories, velocities, tangential and centripetal accelerations of the knots were reconstructed using observational data collected with a single ground-based telescope equipped with a Multi-channel Subtractive Double Pass imaging spectrograph. Lower limits of magnetic fields channeling observed plasma flows were estimated under assumption of the equipartition principle. Assuming approximate electron densities of the plasma n _e=5×10¹¹?cm^?3 in surges and n _e=5×10¹⁰?cm^?3 in quiescent/activated prominences, we found that the magnetic fields channeling two observed surges range from 16 to 40?Gauss, while in quiescent and activated prominences they were less than 10?Gauss. Our results are consistent with previous detections of weak local magnetic fields in the solar prominences.     

Sunspots with the Strongest Magnetic Fields

The strongest observed solar magnetic fields are found in sunspot umbrae and associated light bridges. We investigate systematic measurements of approximately 32 000 sunspot groups observed from 1917 through 2004 using data from Mt. Wilson, Potsdam, Rome and Crimea observatories. Isolated observations from other observatories are also included. Corrections to Mt. Wilson measurements are required and applied. We found 55 groups (0.2%) with at least one sunspot with one magnetic field measurement of at least 4000 G including five measurements of at least 5000 G and one spot with a record field of 6100 G. Although typical strong-field spots are large and show complex structure in white light, others are simple in form. Sometimes the strongest fields are in light bridges that separate opposite polarity umbras. The distribution of strongest measured fields above 3 kG appears to be continuous, following a steep power law with exponent about −9.5. The observed upper limit of 5 – 6 kG is consistent with the idea that an umbral field has a more or less coherent structure down to some depth and then fragments. We find that odd-numbered sunspot cycles usually contain about 30% more total sunspot groups but 60% fewer >3 kG spots than preceding even-numbered cycles.     

Magnetic Flux Imbalance of the Solar and Heliospheric Magnetic Fields

A comparative analysis of solar and heliospheric magnetic fields in terms of their cumulative sums reveals cyclic and long-term changes that appear as a magnetic flux imbalance and alternations of dominant magnetic polarities. The global magnetic flux imbalance of the Sun manifests itself in the solar mean magnetic field (SMMF) signal. The north – south asymmetry of solar activity and the quadrupole mode of the solar magnetic field contribute the most to the observed magnetic flux imbalance. The polarity asymmetry exhibits the Hale magnetic cycle in both the radial and azimuthal components of the interplanetary magnetic field (IMF). Analysis of the cumulative sums of the IMF components clearly reveals cyclic changes in the IMF geometry. The accumulated deviations in the IMF spiral angle from its nominal value also demonstrate long-term changes resulting from a slow increase of the solar wind speed over 1965 – 2006. A predominance of the positive IMF B _z with a significant linear trend in its cumulative signal is interpreted as a manifestation of the relic magnetic field of the Sun. Long-term changes in the IMF B _z are revealed. They demonstrate decadal changes owing to the 11/22-year solar cycle. Long-duration time intervals with a dominant negative B _z component were found in temporal patterns of the cumulative sum of the IMF B _z .     

高能耀斑指数的功率谱及其热点分布

本文采用一个表征高能耀斑强度的综合指数,分析了太阳活动21周以来(1976.7—1991.2)级别≥M1.0的X射线耀斑和能量≥10Mev的质子耀斑综合指数的时空分布,提出在研究时段内太阳上的13个高能耀斑“热点”。这些热点活动区反复回转,爆发了占总指数58.1％的高能耀斑。本文还讨论了高能耀斑热点的特征及其与大尺度磁场演化的关系。结果表明,高能耀斑热点与大尺度磁场的演化关系密切,前者受后者的调制。     

Magnetic Fields of Neutron Stars

This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.     

Magnetic Fields of Neutron Stars

Astronomy Letters - The birth function of neutron stars in magnetic field $$B$$ is estimated for two models of the evolution of radio pulsars corresponding to different directions of evolution of...     

无力磁场的稳定性

无力场被广泛用来模拟太阳活动区的强磁场,本文从Bernstein能量原理出发,导出了无力场能量原理的普遍形式,并给出了若干稳定性的充分条件,它们可方便而有效地对无力场进行稳定性判断。     

非线性无力场模型的线性稳定性

本文从能量原理出发，对无力场稳定性进行了研究，给出了一般情形下无力场稳定性的充要判据。它可以把线性无力场稳定性判据作为特例包括在内。还对Ｋｒｕｇｅｒ给出的一个充分判据作了进一步的探讨，对无力场稳定性的物理图象也作了讨论。     

The Magnetic Field Effect on Planetary Nebulae

In our previous work on the 3-dimensional dynamical structure of planetary nebulae the effect of magnetic field was not considered. Recently Jordan et al. have directly detected magnetic fields in the central stars of some planetary nebulae. This discovery supports the hypothesis that the non-spherical shape of most planetary nebulae is caused by magnetic fields in AGB stars. In this study we focus on the role of initially weak toroidal magnetic fields embedded in a stellar wind in altering the shape of the PN. We found that magnetic pressure is probably influential on the observed shape of most PNe.     

Magnetic Fields and Solar Activities

We discuss the study of solar magnetic fields based on the photospheric vector magnetograms of solar active regions which were obtained at Huairou Solar Observing Station near Beijing in the period of 22nd and 23th solar cycles. The measurements of the chromospheric magnetic field and the spatial configuration of the field at the lower solar atmosphere inferred by the distribution of the solar photospheric and chromospheric magnetic field. After the analysis on the formation process of delta configuration in some super active regions based on the photospheric vector magnetogram observations, some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, proposed to be generated in the subatmosphere, is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and the relationship with magnetic shear in some delta active regions completely. (3) The proposition is that the large-scale delta active regions are formed from contribution by highly sheared non-potential magnetic flux bundles generated in the subatmosphere. We present some results of a study of the magnetic helicity. We also compare these results with other data sets obtained by magnetographs (or Stokes polarimeters) at different observatories, and analyze the basic chirality of the magnetic field in the solar atmosphere.     

High-Resolution Studies of the Solar Polar Magnetic Fields

We present high-resolution studies of the solar polar magnetic fields near sunspot maximum in 1989 and towards sunspot minimum in 1995. We show that, in 1989, the polar latitudes were covered by several unipolar regions of both polarities. In 1995, however, after the polar field reversal was complete, each pole exhibited only one dominant polarity region.Each unipolar region contains magnetic knots of both polarities but the number count of the knots of the dominant polarity exceeds that of the opposite polarity by a ratio of order 4:1, and it is rare to find opposite polarity pairs, i.e., magnetic bipoles.These knots have lifetimes greater than 7 hours but less than 24 hours. We interpret the longitudinal displacement of the knots over a 7-hour period as a measure of the local rotation rate. This rotation rate is found to be generally consistent with Snodgrass' (1983) magnetic rotation law.In an attempt to obtain some insight into the operation of the solar dynamo, sketches of postulated subsurface field configurations corresponding to the observed surface fields at these two epochs of the solar cycle are presented.     

Milestones in the Observations of Cosmic Magnetic Fields

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from anal     

Estimating the Relative Helicity of Coronal Magnetic Fields

To quantify changes of the solar coronal field connectivity during eruptive events, one can use magnetic helicity, which is a measure of the shear or twist of a current-carrying (non-potential) field. To find a physically meaningful quantity, a relative measure, giving the helicity of a current-carrying field with respect to a reference (potential) field, is often evaluated. This requires a knowledge of the three-dimensional vector potential. We present a method to calculate the vector potential for a solenoidal magnetic field as the sum of a Laplacian part and a current-carrying part. The only requirements are the divergence freeness of the Laplacian and current-carrying magnetic field and the sameness of their normal field component on the bounding surface of the considered volume.     

脉冲星磁场的演化

综述了前人对于单个脉冲星磁场的起源和演化的研究结果及其最新进展。脉冲星磁场的起源有多种模型，其所对应的初始磁场有两种位形：磁场束缚在核内和磁场束缚在壳层中。脉冲星的磁场如何演化，没有一致的结论。有各种观测证据可能直接或间接表明磁场的演化行为，如根据特征年龄和运动学年龄的差异可以推断出脉冲星磁场按指数规律衰减，而根据特征年龄与超新星遗迹年龄的差异或几颗年轻脉冲星的制动指数可以认为年轻脉冲星的磁场可能是增强的。脉冲星的样本合成研究（数值模拟）是研究脉冲星磁场演化的重要方法。模拟结果表明，假定脉冲星磁场按指数衰减，特征衰减时标必须为10^7yr或更长。而壳层中磁场的欧姆耗散模型数值计算显示脉冲星磁场演化行为因冷却模型和状态方程的取法不同而异，但最终无明显的衰减。由自转变慢诱导的脉冲星核内部磁场向壳层中扩散模型的计算表明脉冲星磁场的衰减只发生在10^7-10^8yr这段时间内，磁场衰减1－2个量级。     

On Parameters of the Earth-Like Model of Venus

A brief review on the history of constructing Earth-like models of the Venusian interior is presented. Available observational data are analyzed. An explanation for the anomalously large ratio of the quadrupole gravitational moment J₂ to the small parameter of Venus q is proposed. Thus, estimates were obtained for the precession constant and principal moments of inertia for the Earth-like model of Venus.