Short-lived radionuclides in the early solar system — A meteoritic perspective of the solar system formation

This paper reviews the evidence for short-lived radionuclides in the early solar system and evaluates the models of their origin. The stellar model requires that some freshly-nucleosynthesized radionuclides were injected into the proto-solar cloud shortly before it began to collapse. The spallation theory suggests that these nuclides were the products of interaction between energetic particles and gas/dust in the proto-solar cloud or solar nebula. A brief discussion is given to a new theory for the X-wind model of solar system formation.     

An analysis of the observed contrast of solar surface granulation

The contrast of the solar surface granulation detected in the focal plane of the observing system as well as its relations with the aperture of the observing system, the coherent length of atmospheric turbulence and the sensitivity of the detecting system are analyzed. The results of numerical calculation of the granulation contrast as functions of aperture, coherent length of atmospheric turbulence and sensitivity of the detecting system are presented. Results of a related observation are also given.     

Propagation of Alfvén waves in multi-layer solar atmosphere model

In this paper, we idealize the actual solar atmosphere as a multi-isothermal-layer system so as to obtain the energy transmittance of the linear Alfvén wave that propagates through such a system in presence of a uniform oblique magnetic filed. The results indicate that the two-layer model is essentially different to the three-layer one. In the two-layer model, the temperature jump acts as a high pass filter. In the three-layer model, resonant transfer will take place and the transmittance undergoes oscillation as the trigonometric function terms dominate its behavior. For actual solar atmosphere, the result reveals that the lower parts of solar atmosphere are more suitable for those Alfvén waves with period of seconds to transfer their energy.     

Lithium depletion in the solar atmosphere

Using a complete non-local convection theory, we carried out the theoretical calculations of ⁷Li depletion of the solar convective envelope models with different convective parameters c₁ and c₂, and got a model of the solar convection zone consistent with the observed ⁷Li abundance and the depth of the solar convection zone determined by helioseismic techniques. The overshooting distance of effective non-local convective mixing of ⁷Li is very extensive, which is about 1.07H_P or 0.09R. However, the super-radiative temperature zone is much narrower, and it is only 0.20H_P or 0.016R.     

Another mechanism of restricting the lifetime of orbiting satellites

Apsidal resonance causes long periodic variation of large amplitude in the eccentricity of the minor bodies of the solar system (asteroids, natural satellites, artificial satellites of the planets and the moon). Especially for a large-inclination orbiting satellite the increased eccentricity may cause its pericentric distance to decrease below the radius of the primary. This effect, completely different from the dissipative effect of the earth's atmosphere, will be analysed theoretically and illustrated with numerical examples in this paper.     

A model for the coherent emission of solar radio moving type IV bursts

A theoretical model is proposed for interpreting the coherent emissionmechanism of solar radio moving type IV bursts. Energetic electrons produced in flares captured by an expanding and rising magnetic flux tube exhibit a beam-like distribution of velocities on the top of the flux tube. These excite beaming plasma instability and directly amplifies O-mode electromagnetic waves. The instability growth rate sensitively depends on the coronal plasma parameter, ƒ_pe/ƒ_ce and the beam-temperature T_b. This can qualitatively explain the high brightness temperature and high degree of polarization as well as the broad spectrum observed in this type of solar radio bursts.     

太阳系小天体运动的稳定区域

概述了太阳系中卫星型、行量型和类Trojan群型小天体运动的稳定区域问题的现有研究结果,提出了几个有待于进一步深入研究的重要课题．     

Interaction between sheared flow and resistive tearing mode

We investigate the nonlinear evolution of resistive tearing mode in a current sheet with a sheared flow in a long, thin cylinder. The results show that a hyperbolic secant (sech) flow field will lead to instability of the resistive tearing mode, formation of magnetic islands and rapid release of magnetic energy. The coupling between sheared flow and the tearing mode and interaction between suprathermal instabilities change the degree of shear in the magnetic field (the electric current gradient) and drive the development of the instability. This process may be one of the mechanisms of solar flares.     

Solar and stellar flares: Questions and problems

Although progress has been made in understanding certain aspects of the physics of solar and stellar flares, there are a number of topics which, in the author's opinion, still pose a problem. We summarize these topics here.     

Cyclical variability of prominences, CMEs and flares

Solar flares, prominences and CMEs are well known manifestations of solar activity. For many years, qualitative studies were made about the cyclical behaviour of such phenomena. Nowadays, more quantitative studies have been undertaken with the aim to understand the solar cycle dependence of such phenomena as well as peculiar behaviour, such as asymmetries and periodicities, occurring within the solar cycle. Here, we plan to review the more recent research concerning all these topics.     

Two-dimensional MHD equilibria in the solar corona

Using a combined analytical and numerical Method we have treated the question of two-dimensional MHD equilibriam in an inviscid compressible, perfect conducting plasma with an embedded magnetic field in the spherically symmetric gravitational field of the sun. Two solutions are obtained. (1) A steady, self-consistent plasma flow in a magnetic field with both a closed and an open region. In the open region, beyond a few solar radii, the plasma velocity exceeds the local sound and Alfvén velocities. (2) The plasma velocity is everywhere smaller than the local sound and Alfvén velocities and tends to zero at large radial distances.     

A brief description of observational results from the supersoft X-ray detector aboard Shenzhou-2

Observational results from the supersoft X-ray detector (SD) aboard the spacecraft Shenzhou-2 are briefly described. The resultspertain to cosmic γ-ray bursts solar x-ray bursts, high-energy charged particles and soft X-ray background radiation. The detector is a proportional counter with a polypropylene thin-film window of 50 mm diameter, it operates in the energy range 0.23–3.0keV covered by six energy channels. Two grades of time resolution are used: 40 ms for recording burst events and 520 ms when there is no triggering signal resulted from a burst event. Figures 1 and 2 show the light curves and energy spectra of two cosmic γ-ray bursts (starting time 2001 Jan 17, 09:37:25.21 UT and 2001 Mar 9, 12:33:55.692 UT), and Figures 3 and 4, the results on two solar X-ray burst (2001 Apr 6, 19:14:09.11 UT, and 2001 May 20, 06:02:12.58 UT). The detector records the ambient high-energy charged particles when there is no burst event and the shutter of the window is closed. 110 data sets of high-energy charged particles along the spacecraft orbit have been collected. As examples, the variations of the particle counting rate along the orbit are shown in Figs. 6a, 6b, 8e, 8f and 7. More than 10 events of particle precipitation induced by solar proton events have also been recorded, some of which are displayed in Figs.6c–6f and 7. Some of the data of soft X-ray background radiation shown in Fig. 8 were obtained when the shutter was open, and they are important for the data processing of the burst events.     

太阳风离子尺度湍流与太阳风加热

太阳风源自太阳大气,在行星际空间传播过程中被持续加热,然而究竟是何种能量加热了太阳风至今未研究清楚.太阳风普遍处于湍动状态,其湍动能量被认为是加热太阳风的重要能源.然而,太阳风湍流通过何种载体、基于何种微观物理机制加热了太阳风尚不明确,这是相关研究的关键问题.将回顾人类对太阳风加热问题的研究历史,着重介绍近年来我国学者在太阳风离子尺度湍流与加热方面取得的研究进展,展望未来在太阳风加热研究中有待解决的科学问题和可能的研究方向.     

Unsolved Problems of Celestial Mechanics — The Solar System

The Unsolved Problems of Celestial Mechanics for the Solar System are divided here into six distinct topics, (1) discrepancies between observations and ephemerides, (2) formation and stability of the solar system, (3) resonances, (4) theories, (5) reference systems, and (6) artificial satellites.This paper was presented as an invited paper at a session of Commission 7, Celestial Mechanics, at the IAU General Assembly in New Delhi, India, in November 1985.     

Energetic particles from the sun

This paper discusses solar cosmic ray phenomena and related topics from the solar physical point of view. Basic physics of the solar atmosphere and solar flare phenomena are, therefore, considered in some detail. Since solar cosmic rays are usually produced by solar flares, we must first understand the processes and mechanism of solar flares, especially the so-called proton flares, in order to understand the acceleration mechanism of solar cosmic rays and their behaviour in both the solar atmosphere and interplanetary space. For this reason, detailed discussion is given on various phenomena associated with solar flares, proton flare characteristics, and the mechanism of solar flares.Since the discovery of solar cosmic rays by Forbush, the interplanetary space has been thought of as medium in which solar cosmic rays propagate. In this paper, the propagation of solar cosmic rays in this space is, therefore, discussed briefly by referring to the observed magnetic properties of this space. Finally, some problems related to the physics of galactic cosmic rays are discussed.Astrophysics and Space Science Review Paper.     

A rope-shaped solar filament and a IIIb flare

On September 14–18, 2000, a medium-small solar active region was observed at Ganyu Station of Purple Mountain Observatory. Its spots were not large, but it had a peculiar active filament. On Sep.16, a flare of importance III_b with rather intense geophysical effects was produced. Our computation of the magnetic structure of the active region reveals that the rope-shaped filament was concerned with a low magnetic arc close to magnetic neutral line. An intense shear of magnetic field occurred near magnetic rope. The QSL analysis shows that a 3-D magnetic reconnection might appear in the vicinity of filament, and this can be used to interpret the formation of a large flare.     

太阳剧烈活动与空间灾害天气

剧烈太阳活动和空间灾害天气的研究 ,是当代空间科学中最前沿、最具挑战性和最能造福人类的课题。这一研究将揭示太阳活动的成因、证认太阳活动和空间灾害天气的因果联系 ,在天文、空间和地球科学交叉领域取得实质性的学科进步 ,为实施我国国家空间天气计划提供坚实的科学基础 ,为发展我国空间科学探测准备新的概念和思路。本文评述了国家基础研究重点规划 (973)项目“剧烈太阳活动与空间灾害天气”的研究进展、科学机遇和进一步努力方向。     

Dynamics of the solar magnetic field from SOHO/MDI

The investigation of the dynamics of magnetic fields from small scales to the large scales is very important for the understanding of the nature of solar activity. It is also the base for producing adequate models of the solar cycle with the purpose to predict the level of solar activity. Since December 1995 the Michelson Doppler Imager (MDI) on board of the Solar and Heliospheric Observatory (SOHO) provides full disk magnetograms and synoptic maps which cover the period of solar cycle 23 and the current minimum. In this paper, I review the following important topics with a focus on the dynamics of the solar magnetic field. The synoptic structure of the solar cycle; the birth of the solar cycle (overlapping cycles 23 and 24); the relationship of the photospheric magnetic activity and the EUV solar corona, polar magnetic fields and dynamo theory (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The magnetic field in the solar atmosphere

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.