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Study of the primordial lithium abundance

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Science China(Physics,Mechanics & Astronomy) 2011年第S1期54卷 67-72页

作者： LI ZhiHong1, LI ErTao1, SU Jun1, LI YunJu1, BAI XiXiang1, GUO Bing1, WANG YouBao1, CHEN YongShou1, HOU SuQing1, ZENG Sheng1, LIAN Gang1, SHI JianRong2.& LIU WeiPing1 1 China Institute of Atomic Energy, beijing 102.13, China 2.ational astronomical Observatories,{2., beijing 100012, China China Inst Atom Energy Beijing 102413 Peoples R China chinese Acad Sci Natl Astron Observ Beijing 100012 Peoples R China

Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, beijing. The Standard BBN (SBBN) network calculations are then performed to investigate the primordial Lithium abundance. The result shows that these nuclear reactions have minimal effect on the SBBN abundances of 6Li and 7Li.

关键词： big bang nucleosynthesis element abundance nuclear reaction network

Solar Flare Activity and Variability of Electric Current Helicity

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chinese Journal of Astronomy and Astrophysics 2002年第1期2卷 81-91页

作者： KimJikSu Hong－QiZhang 等 PyongyangastronomicalObservatory AcademyofSciencesDPRofKorea NationalastronomicalObservatories ChineseAcademyofSciencesBeijing100012

Recent study using Huairou vector magnetograph data shows that durlug flare activity, the current helicity exhibits rapid and substantial variations and, in some cases, a recovering phase. We considered various representative the magnetic configurations. First, interacting twisted magnetic flux tubes are analyzed separately for positive, negative and mixed-sign helicity regions. The results show that the helicity during flares decreases in positive-sign, and increases in negative-sign regions. Then, flaring arcade also shows that the magnitude of the helicity decreases after flares. We also investigated current sheets formed by sheared magnetic field and showed that the current helicity (with either positive and negative signs) vanishes after reconnection. The emergence of twisted flux tubes which can trigger flares may be another source of flare-associated variability of current helicity. We demonstrate the relevance of current helicity to the description of flare activity by comparing its variation with that of shear angle in the active region AR 6891.

关键词： Sun: flare -Sun: current helicity - Sun: magnetic shear

Atmospheric Excitation of Time Variable Length-of-Day on Seasonal Scales

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chinese Journal of Astronomy and Astrophysics 2006年第1期6卷 120-124页

作者： Li-Hua Ma Yan-Ben Han National astronomical Observatories Chinese Academy of Sciences Beijing 100012

We use the method of wavelet transform to analyze the time series of the Earth＇s rotation rate of the EOP （IERS） C04. The result shows that the seasonal （annual and semiannual） variation of the length-of-day （LOD） has temporal variability in its period length and amplitude. During 1965.0-2.01.0, the periods of the semiannual and annual components varied mainly from 175-day to 190-day and from 360-day to 370-day, respectively; while their amplitudes varied by more than 0.2.ms and 0.1 ms, respectively. Analyzing the axial component of atmospheric angular momentum （AAM） during this period, we have found that time-variations of period lengths and amplitudes also exist in the seasonal oscillations of the axial AAM and are in good consistency with those of the seasonal LOD change. The time variation of the axial AAM can explain largely the change of the LOD on seasonal scales.

关键词： Earth rotation -- seasonal variation -- wavelet transform

On the Lower Energy Cutoff of Nonthermal Electrons in Solar Flares

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 453-459页

作者： Wei－QunGan You－PingLi 等 PurplemountainObservatory ChineseAcademyofSciencesNanjing210008 NationalastronomicalObservatories Ch

A quantitative method to determine the lower energy cutoff (Ec) of power-law electron beams is established. We apply this method to the 54 hard X-ray events observed with BATSE/Compton Gamma Ray Observatory (CGRO). The results show that about 75% of the observed broken double power-law spectra of hard X-rays can be explained by a lower energy cutoff in the power-law electron beams. The values of Ec, varying among the flares, are all greater than the usually accepted 2. keV! On average, E~ is about 69 keV. So high a lower energy cutoff of nonthermal electrons implies that nonthermal electrons might not be as important in powering solar flares as was previously thought. Further significance of this finding is discussed.

关键词： Sun: hard X-rays - Sun: gamma-rays - Sun: flares - Sun: particles TheSun

A comparative analysis on two solar proton events

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chinese Science Bulletin 2007年第1期52卷 47-51页

作者： LE GuiMing1,2.3,4, HAN YanBen2.& ZHANG YiJun3 1 Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, China Meteorological Administration, beijing 100081, China 2.National astronomical Observatories,{2., beijing 100012, China 3 chinese academy of Meteorological sciences, China Meteorological Administration, beijing 100081, China 4 National Center for Space Weather, China Meteorological Administration, beijing 100081, China Key Laboratory of Radiometric Calibration and Validation for EnvironmentalSatellites China Meteorological Administration Beijing 100081 China

This paper presents a comparative analysis on the two Solar Proton Events (SPE), which occurred on 14 July 2.00 (Bastille Day) and 2. October 2.03 (2.OCT03) respectively. It is found that although the peak flux of the latter seemed to be greater than that of the former based on geostationary observations, the maximum intensities of the energetic protons (>10 MeV and 30 MeV) during the Bastille Day event were all higher than those of the 2.OCT03 event according to the interplanetary observations. Further analysis indicated that the quantity of the seed particles, which could be accelerated to the energies exceeding 10 and 30 MeV by the Coronal Mass Ejection (CME)-driven shock on 14 July 2.00, was far larger than that of the 2.OCT03 event. In the Bastille Day case, when the CME approached to the height around 14 R⊙, the CME-driven shock would reach its maximum capacity in accelerating the solar en- ergetic protons (>100 MeV). In contrast, on 2. October 2.03, when CME approached to the height about 58R⊙, the CME-driven shock reached its highest potential in accelerating the solar energetic protons of the same category. At this moment, the peak flux (>100 MeV) was about 155 pfu, which was much lower than 355 pfu measured on 14 July 2.00. This demonstrated that in the Bastille Day event, the quantity of the seed particles, which could be accelerated to the energy beyond 100 MeV, was significantly larger than its counterpart in the 2.OCT03 case. Therefore, the peak flux of an SPE event depends not only on the interplanetary intensity of the solar energetic particles, but also on the velocity of the associated CME-driven shock, and the quantity of the seed particles as well as on the interplanetary magnetic en- vironment. This paper also reveals that the magnetic sheath associated with ICME on 2. October 2.03 captured a large number of solar energetic protons, including those having energy greater than 100 MeV.

关键词：太阳质子 CME 太阳耀斑太阳系

Two-fluid Dynamics in Clusters of Galaxies

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chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 6-20页

作者： Yu-Qing LouNational astronomical Observatories, chinese academy of sciences,{2.Department of Physics & Tsinghua Center for Astrophysics (THCA), Tsinghua University, beijing 100084 Department of Astronomy and Astrophysics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 USA National astronomical Observatories Chinese Academy of Sciences Beijing 100012

We develop a theoretical formulation for the large-scale dynamics of galaxy clusters involving two spherical 'isothermal fluids' coupled by their mutual gravity and derive asymptotic similarity solutions analytically. One of the fluids roughly approximates the massive dark matter halo, while the other describes the hot gas, the relatively small mass contribution from the galaxies being subsumed in the gas. By properly choosing the self-similar variables, it is possible to consistently transform the set of time-dependent two-fluid equations of spherical symmetry with self-gravity into a set of coupled nonlinear ordinary differential equations (ODEs). We focus on the analytical analysis and discuss applications of the solutions to galaxy clusters.

关键词： dark matter - hydrodynamics - ISM: general - galaxies: clusters -outflows winds - shocks

Evolution of Vertical Electric Currents and Flares in An Active Region

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天文研究与技术 1999年第S1期 419-423页

作者： Li Wei 1, 2., Ai Guoxiang 1, 2.1 (beijing astronomical Observatory, The{2., beijing 100012, China) 2.(National astronomical Observatories, The{2., beijing 100012, China)

In this paper, solar active region (AR) 6891 is studied. The long term temporal (over a 8 day period) relationahip between vertical current evolution and flare are examined. We found that the day to day variation of the flare number in the active region is more closly associated with the variation of net current intensity than that of total current intensity. The increase in negative current in the weak following polarity area is due to the reduction in negative current in the strong preceding area.

关键词： in An Active Region Evolution of Vertical Electric Currents and Flares

Statistics of Galactic Supernova Remnants

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chinese Journal of Astronomy and Astrophysics 2005年第2期5卷 165-174页

作者： Jian-WenXu Xi-ZhenZhang Jin-LinHan NationalastronomicalObservatories ChineseAcademyofSciencesBeijing100012

We collected the basic parameters of 2.1 supernova remnants (SNRs) in ourGalaxy, namely, distances (d) from the Sun, linear diameters (D), Galactic heights (Z), estimatedages (t), luminosities (L), surface brightness (Σ) and flux densities (S_1) at 1-GHz frequency andspectral indices (α). We tried to find possible correlations between these parameters. As expected,the linear diameters were found to increase with ages for the shell-type remnants, and also to havea tendency to increase with the Galactic heights. Both the surface brightness and luminosity ofSNRs at 1-GHz tend to decrease with the linear diameter and with age. No other relations between theparameters were found.

关键词： methods: statistical (ISM:) supernova remnants

Petrology and mineral chemistry of new ureilites found in Grove Mountains, Antarctica

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Progress in Natural Science:Materials International 2008年第4期18卷 431-439页

作者： Bingkui Miaoa,b,, Yangting Linb, Guiqin Wangc, Daode Wangc, Ziyuan Ouyangd a Key Laboratory of Geological Engineering Center of Guangxi Province, Guilin University of Technology, Guilin 541004, China b State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, chinese academy of sciences, beijing 10002., China c Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, chinese academy of sciences, Guangzhou 510640, Chinad National astronomical Observatories, chinese academy of sciences, beijing 100012, China Key Laboratory of Geological Engineering Center of Guangxi Province Guilin University of Technology Guilin 541004 China State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou 510640 China National astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Petrography and mineral chemistry of two new ureilites, GRV 02.512.and 02.931, from the Grove Mountains, Antarctica, are reported in this paper. GRV 02.512.exhibits a typical ureilite texture, and consists of 48.3% olivine, 9.4% pigeonite and 38.1% carbo- naceous interstitial material and/or reduction product. GRV 02.931 has a cataclastic porphyritic texture, and consists of 19.1% olivine and 14.1% pigeonite embedded in 66.3% carbonaceous interstitial material and/or reduction product. The coarse-grained olivine and pigeonite in both meteorites have homogeneous cores, and they are FeO-rich within the range of the ferroan subgroup (subgroup I) of olivine-pigeonite ureilites. All olivine grains of the meteorites show reduction zones along boundaries and cracks. Abundant diamond coexists with graphite as graphite-rich patches and veins in the carbonaceous interstitial material. Petrogenesis of both meteorites and the origin of diamond are discussed.

关键词： Meteorite Achondrite Ureilite Diamond Antarctica