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Studies of solar flares and CMEs related to the space solar missions in the future

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Science china(Physics,Mechanics & Astronomy) 2009年第11期52卷 1646-1654页

作者： lin jun1,2. National astronomical {2./yunnan astronomical observatory, chinese academy of sciences, kunming 650011, china 2.Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02.38, USA National astronomical observatories/{2. astronomical observatory Chinese Academy of Sciences Kunming China Harvard-Smithsonian Center for Astrophysics Cambridge USA

Solar eruptions and the related processes involve magnetic fields and plasma flows of various scales in both time and space. These processes include the convective motions of the mass and magnetic field in the photosphere, evolutions of magnetic fields in both the chromosphere and the corona prior to and during the disruption of magnetic fields in response to the photospheric motions. These evolutions constitute a whole process of transporting the magnetic energy and the helicity from the photosphere to the corona, and then to interplanetary space. The present work, on the basis of a solar eruption model, discusses these processes, and the related questions, unanswerable at present, but could be the scientific objectives of the space solar missions in the future.

关键词： solar eruptions magnetic field energy conversion magnetic reconnection current sheet

Temporal variation of hemispheric solar rotation

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Research in Astronomy and Astrophysics 2012年第2期12卷 187-200页

作者： Jing-Lan Xie 1,2.Xiang-jun Shi 1,2.and Jing-Chen Xu 1,2. National astronomical {2. /yunnan observatory,chinese academy of sciences,kunming 650011,china 2.Graduate University of chinese academy of sciences,Beijing 100049,china National astronomical observatories/ {2. observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese academy of sciences Beijing 100049 China

The daily sunspot numbers of the whole disk as well as the northern and southern hemispheres from 1945 January 1 to 2.10 December 31 are used to investi- gate the temporal variation of rotational cycle length through the continuous wavelet transformation analysis method. Auto-correlation function analysis of daily hemi- spheric sunspot numbers shows that the southern hemisphere rotates faster than the northern hemisphere. The results obtained from the wavelet transformation analysis are that no direct relationship exists between the variation trend of the rotational cy- cle length and the solar activity in the two hemispheres and that the rotational cycle length of both hemispheres has no significant period appearing at 11 yr, but has a sig- nificant period of about 7.6 yr. Analysis concerning the solar cycle dependence of the rotational cycle length shows that acceleration seems to appear before the minimum time of solar activity in the whole disk and the northern hemisphere, respectively. Furthermore, the cross-correlation study indicates that the rotational cycle length of the two hemispheres has different phases, and that the rotational cycle length of the whole disk as well as the northern and southern hemispheres, also has phase shifts with corresponding solar activity. In addition, the temporal variation of the north-south （N- S） asymmetry of the rotational cycle length is also studied. This displays the same variation trend as the N-S asymmetry of solar activity in a solar cycle, as well as in the considered time interval, and has two significant periods of 7.7 and 17.5 yr. Moreover, the rotational cycle length and the N-S asymmetry of solar activity are highly corre- lated. It is inferred that the northern hemisphere should rotate faster at the beginning of solar cycle 2..

关键词： Sun: activity - Sun: rotation - Sun: sunspot

Observational Features of Large-Scale Structures as Revealed by the Catastrophe Model of Solar Eruptions

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chinese Journal of Astronomy and Astrophysics 2007年第4期7卷 457-476页

作者： jun lin National {2. observatories/yunnan observatory, chinese academy of sciences, kunming 650011 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02.38, USA National astronomical observatories / {2. observatory Chinese Academy of Sciences Kunming 650011 Harvard-Smithsonian Center for Astrophysics 60 Garden Street Cambridge MA 02138 USA

Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material through a series of equilibrium configurations. The motion brings energy into the coronal magnetic field until the system ceases to be in equilibrium. The catastrophe theory for solar eruptions indicates that loss of mechanical equilibrium constitutes the main trigger mechanism of major eruptions, usually shown up as solar flares, eruptive prominences, and coronal mass ejections （CMEs）. Magnetic reconnection which takes place at the very beginning of the eruption as a result of plasma instabilities/turbulence inside the current sheet, converts magnetic energy into heating and kinetic energy that are responsible for solar flares, and for accelerating both plasma ejecta （flows and CMEs） and energetic particles. Various manifestations are thus related to one another, and the physics behind these relationships is catastrophe and magnetic reconnection. This work reports on recent progress in both theoretical research and observations on eruptive phenomena showing the above manifestations. We start by displaying the properties of large-scale structures in the corona and the related magnetic fields prior to an eruption, and show various morphological features of the disrupting magnetic fields. Then, in the framework of the catastrophe theory, we look into the physics behind those features investigated in a succession of previous works, and discuss the approaches they used.

关键词： Sun: large-scale magnetic structures - Sun: eruptive processes - Sun: theory and observations - magnetic reconnection and current sheets

Avoided crossings between non-radial modes in low mass RGB stars

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Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： jun-jun Guo1,2.3,Yan Li1,2.and Xiang-jun Lai1,2.1 National astronomical observatories/yunnan observatory,chinese academy of sciences, kunming 650011,china 2.Key Laboratory for the Structure and Evolution of Celestial Objects,chinese academy of sciences,kunming 650011,china 3 Graduate University of chinese academy of sciences,Beijing 100049,china National astronomical observatories/{2. observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese academy of sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2.and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2.and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2.and 3 in frequency and periodéchelle diagrams and find modes of l=2.and 3 fit the two relations better;they are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2.and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2.and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2.and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

A cyclic behavior of CME accelerations for accelerating and decelerating events

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Research in Astronomy and Astrophysics 2009年第10期9卷 1165-1172页

作者： Peng-Xin Gao Ke-jun Li National astronomical observatories / {2. observatory Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese academy of sciences Beijing 100049 China

We investigate the cyclic evolutionary behavior of CME accelerations for accelerating and decelerating CME events in cycle 2. from 1997 January to 2.07 December. It is found that the absolute values of semiannual mean accelerations of both accelerating and decelerating CME events roughly wax and wane in a cycle, delaying the sunspot cycle in time phase. We also investigate the semiannual number of CMEs with positive and neg- ative acceleration and find that there are more decelerating CME events than accelerating CME events during the maximum period of a cycle （about three years）, but there are more accelerating CME events than decelerating CME events during the rest of the time interval of the cycle. Our results seem to suggest that the different driving mechanisms may be acting accelerate and decelerate CME events; for accelerating CME events, the propelling force （Fp） statistically seems to play a significant role in pushing CMEs outward; for decelerating CME events, the drag （Fd） statistically seems to play a more effective role in determining CME kinematic evolution in the outer corona. During the maximum period of a cycle, because of the V^2.dependence, Fd is generally stronger; because of the magnetic field dependence, Fp is also generally stronger. Thus, the absolute values of both the negative and positive accelerations are generally larger during that time. Because of the V^2.dependence, Fd may be more effective during the maximum period of a cycle. Hence, there are more decelerating CME events than accelerating CME events during that time. During the minimum time interval of a cycle, CMEs have relatively small speeds, and Fp may be more effective. Therefore, there are more accelerating CME events than decelerating CME events during that time.

关键词： Sun corona -- Sun coronal mass ejections (CMEs)

Can Asymmetry of Solar Activity be Extended into Extended Cycle?

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chinese Journal of Astronomy and Astrophysics 2002年第1期2卷 66-70页

作者： Ke－junLi Jing－XiuWang 等 yunnanobservatory ChineseAcademyofSciencesKunming650011 Nationalastronomicalobservatories ChineseAcademyofSciencesBeijing100012

With the use of the Royal Greenwich observatory data set of sunspot groups, an attempt is made to examine the north-south asymmetry of solar activity in the 'extended' solar cycles. It is inferred that the asymmetry e... 详细信息

关键词： Sun: sunspot - Sun: active cycle - Sun: activity

Three-dimensional Distribution of the Escape Photons of Hα Flares

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chinese Journal of Astronomy and Astrophysics 2006年第1期6卷 87-95页

作者： Ming-Guo Sun Zhong-Quan Qu Zhi Xu Xiao-Yu Zhang Cheng-lin XU Shuai Wang Chun-Lan Jin yunnan astronomical {2./National astronomical observatories Chinese Academy ofn Sciences Kunming 650011 Department of Astronomy Nanjing University Nanjing 210093 Graduate University of the chinese academy of sciences Beijing 100049

A technique for obtaining a three-dimensional distribution of received photons in Hα flares in the solar atmosphere is presented. It is well known that during flares hydrogen atoms in the chromosphere and photosphere are excited （even ionized） by the downward heating of non-thermal particles and then emit Hα photons. We trace back these Hα photons to their original layers by use of the contribution function in the theory of spectral line formation, and so acquire their three-dimensional （3D） distribution. This technique is applied to the two-ribbon flare of 2.02.January 2.. The atmospheric models are obtained by fitting the ＂quasi-profiles＂ with the help of the generally used model atmospheres. Since the variety of the 3D images reflects the response of the atmospheric layers to the impact of energy transport, an analysis of the development of the flare is given through a comparison of the 3D images with the 2. temperature distribution.

关键词： line: formation - radiative transfer - sun: flares

The Chiralities of Three Filaments in AR7500

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天文研究与技术 1999年第S1期 433-437页

作者： Jiang Yunchun 1,2.3 , Luan Di 1,2., lin Ganghua 1,3 , Wang Jingxiu 1,3 1 (National astronomical {2., The chinese academy of sciences, Beijing 100012. china) 2.(yunnan observatory, The chinese academy of sciences, kunming 65001

An analysis of structure and evolution of three filaments in AR7500 ON May, 1993 is presented. The three filaments show the following remarkable peculiarities: 1) a sinistral filament lies between two dextral filaments and meets them at two cusps. One of the cusps is rooted in positive polarity plage region while the other in a small decaying spot with negative polarity. 2. Both chromospheric plagette associated fibrils near the filaments and the transverse magnetic fields of the photosphere beneath the filaments almost parallel to the long axis of these filaments, suggesting the dominance of axial field of filaments; the spots near filament’s ends, however, do not show clearly counterclockwise or clockwise superpenumbral fibril pattern. 3) The three filaments do not merge into a single filament during 8 day observation. This can be explained by considering that the magnetic fields along their long axes are in different directions at two cusps. When one of dextral filaments and the sinistral filarment eventually dissipate into fibrils connecting the opposite polarity regions, their jointing cusps can be still clearly observed due to their opposite chiralities.

关键词： Sun: filament Sun:magnetic field

一个复杂太阳射电爆发及其微波源和远紫外冕环特征的初步研究

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天文学报 2004年第4期45卷 389-401页

作者：王霖谢瑞祥汪敏许春刘玉英中国科学院国家天文台云南天文台昆明650011 中国科学院国家天史台北京100012

利用太阳射电宽带频谱仪(0.7-7.6 GHz)于2.01年10月19目观测到的复杂太阳射电大爆发,呈现出许多有趣的特征.结合NoRH(Nobevama Radio Heliograph)的高空间分辨率射电成像观测及TRACE(Transition Region and Coronal Explorer)在远紫外(EUV)波段的高空间分辨率成像观测资料,分析了该爆发的射电频谱特征和微波射电源的演化以及它们与复杂的EUV日冕环系统的关系.该爆发是一个双带大耀斑的射电表征.前一部分以宽带(从厘米到米波)爆发为主,机制是回旋同步辐射,所对应的是环足源的辐射;后一部分以窄带(分米到米波)分米波爆发为主,机制是等离子体辐射和回旋共振辐射的联合,对应的是环顶源的辐射.

关键词：太阳射电爆发射电源耀斑日冕观测资料微波源演化 EUV 米波宽带