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How to estimate the effect of an intense meteor shower on human space activities

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Science China(Physics,Mechanics & Astronomy) 2009年第8期52卷 1161-1168页

作者： WU GuangJie National Astronomical observatories/yunnan {2.,chinese academy of sciences,kunming 650011,China National Astronomical observatories/yunnan {2. Chinese Academy of Sciences Kunming 650011 China

In the present age,the potential threat to space projects coming from some intense meteor storms has been ***,the increasing activities of mankind in space for scientific,commercial and military purposes have led to an increase in safety-related problems about the satellites,space stations and *** new techniques for observing meteors and meteor showers have been ***,how to estimate even predict the effect of an intense meteor shower should be further *** initial definition about a meteor storm based on visual observations with a Zenithal Hourly Rate of over one thousand seems insufficient,since it only means a storm or burst of meteors in *** 2.06 the author suggested a synthetical index of the potential threats about intense activities of meteors;however,it is too complex to determine several *** this paper,the author suggests a Special True Number Flux Density(STNFD).Set a certain energy-limit,or a certain electric-charge-limit,and then calculate the number flux *** the comparison between two of the 10 strong meteor showers in recent years it is found that the important factor affecting the space flight security is not only the number of meteoroids,but also their velocities,their average energy and the population index *** show that Giacobinids,even June Bootids,should be one of the most hazardous meteor showers.

关键词： meteors meteorites and tektites spacecraft/atmosphere interactions observation and data reduction techniques

An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I. Hydrodynamics

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chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 680-688页

作者： Cong yu National Astronomical observatories / {2. Astronomical observatory, chinese academy of sciences, kunming 650011 Graduate School of chinese academy of sciences, Beijing 100049 Graduate School of chinese academy of sciences Beijing 100049

Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrodynamic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory （WENO） scheme to fifth order accuracy in space, lILLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing （TVD） Runge-Kutta scheme. Extensive testing and comparison with schemes that *** characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.

关键词： accretion - hydrodynamics- method numerical - shock waves

A Test on Different Types of the Time Curve of Hardness Ratio of Gamma-Ray Bursts based on the Curvature Effect

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chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 451-464页

作者： lan-Wei Jia National Astronomical observatories/{2. observatory,chinese academy of sciences,kunming 650011,China Graduate School of chinese academy of sciences,Beijing 100049,China National Astronomical observatories/ yunnan observatory Chinese Academy of Sciences Kunming 650011 China and Graduate School of chinese academy of sciences Beijing 100049 China

We analyzed a sample of 66 gamma-ray bursts （GRBs） and statistically confirmed the prediction on the time curve of the hardness ratio of GRBs made by Qin et al. based on the curvature effect. In their analysis, GRB pulses are divided into three types according to the shape of their raw hardness ratio （RHR） time curves, defined as to include the background counts to the signal counts, so as to make use of counts within small time intervals. Of the three types, very hard sources exhibit a perfect pulse-like profile （type 1）, hard bursts possess a pulse-like profile with a dip in the decay phase （type 2., and soft bursts show no pulse-like profile but have only a dipped profile （type 3）. In terms of the conventional hardness ratio, type 3 sources are indeed generally softer than those of type 1 and type 2. in agreement with the prediction. We found that the minimum value of RHR is sensitive in distinguishing the different types. We propose that GRB pulses can be classified according to the minimum value of RHR and that the different type sources may be connected with different strengths of the shock or/and the magnetic field.

关键词： gamma-rays burst -- gamma-rays observations - methods statistical

An Alternative Explanation for a Screw-like Meteoric Train Photographed by Double-Station Observations

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chinese Journal of Astronomy and Astrophysics 2007年第6期7卷 814-822页

作者： Guang-Jie Wu1,2.1 National Astronomical observatories/yunnan {2.,chinese academy of sciences,kunming 650011 2.Purple Mountain {2.,chinese academy of sciences,Nanjing 2.0008 Purple Mountain observatory Chinese Academy of Sciences Nanjing 210008

Two-station observation of meteors, especially a meteor trains, provides an effective approach to the measurement of the physical parameters. We have collected four special groups of photographs of meteoric trains taken at two stations during Leonids 2.01. One representative group has been measured and analyzed in detail. An analysis has been reported in our first paper. In this paper, an alternative explanation for the screw-like meteoric train is suggested based on some physical calculations. The results reveal that this train has a screw-like structure and, apparently, spoke beams. The mother meteor of this train may be negatively charged and moves forward along a left-hand screw trajectory under the effect of the geomagnetic field. The spoke beams might be the visual effect of the long time exposure of many particles released from the disintegrated meteoroid.

关键词： meteors meteoroids -- magnetic fields

What does the Sun tell and hint now?

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Research in Astronomy and Astrophysics 2009年第9期9卷 959-965页

作者： Ke-Jun Li1,2.1 National Astronomical observatories /yunnan {2.,chinese academy of sciences,kunming 650011,China 2.Key Laboratory of Solar Activity,National Astronomical observatories,chinese academy of sciences,Beijing 100012.China National Astronomical observatories/yunnan {2. Chinese Academy of Sciences Kunming 650011 China Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Some historical records, which have held since the beginning of modern solar activity cycles, are being broken by the present Sun： cycle 2. records the longest cycle length and fall time; latitudes of high-latitude sunspots belonging to a new cycle around the minimum time of the cycle are statistically the lowest at present, compared with those of other cycles; there are only one or no sunspots in a month appearing at high latitudes for 58 months, which is the first time that such a long duration has been observed. The solar dynamo is believed to be slowing down due to：（1） the minimum smoothed monthly mean sunspot number is the smallest since cycle 16 onwards, and even probably among all modern solar cycles; and （2. once the time interval between the first observations of two neighboring sunspot groups is larger than 14 d, it should be approximately regarded as an observation of no sunspots on the visible solar disk, called a spotless event. Spotless events occur with the highest frequency around the minimum time of cycle 2., and the longest spotless event also appears around the minimum time for observations of the Sun since cycle 16. Cycle 2. is expected to have the lowest level of sunspot activity from cycle 16 onwards and even probably for all of the modern solar cycles.

关键词： Sun: activity -- Sun: general -- sunspots

The Chemical Classification of the AGB Star IRAS 17515-2.07

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chinese Journal of Astronomy and Astrophysics 2003年第6期3卷 551-554页

作者： Pei-Sheng Chen and Pin Zhang1National Astronomical observatories, yunnan observatory,{2., kunming 650011 2.osmic Ray Institute, yunnan University, kunming 650091 Cosmic Ray Institute Yunnan University Kunming 650091

The chemical classification of IRAS 17515-2.07 has been debated for a longtime. Up to now there are two contenders, oxygen-rich or carbon-rich. We believe that IRAS17515-2.07 is an oxygen-rich source: because (ⅰ) it shows the silicate self-absorbed emission; (ⅱ)in the near infrared-IRAS diagram it is located in the oxygen-rich object region and (ⅲ)particularly, it has detected SiO maser emission.

关键词： stars: AGB stars: chemical classification stars: maser infrared: stars

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 observatories /{2. observatory,chinese academy of sciences,kunming 650011,China 2.Graduate University of chinese academy of sciences,Beijing 100049,China National Astronomical observatories/ yunnan 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

The relationship of extended radio power and broad emission line luminosity in blazars

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Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 240-243页

作者： LIU HongTao & Bai JinMing National Astronomical observatories/yunnan {2.,chinese academy of sciences,kunming 650011,China chinese Acad Sci Yunnan Observ Natl Astron Observ Kunming 650011 Peoples R China

The relationship between broad line luminosity LBLR and extended radio power PE is *** the log PE-log LBLR diagram,FSRQs populate the region of higher luminosity relative to BL Lacs,and FR II BL Lacs are between FSRQs and FR I BL *** these blazars,there is a significant correlation between LBLR and *** regression line scales as PE ∝ L0B.L87R ± *** slope of this scaling relation is consistent with that derived from the simple theoretical ***,the unification of BL Lacs and FRSQs into a single population finds a statistical basis,and a disk-jet symbiosis in blazars is *** II BL Lacs are probably at an intermediate stage in the sequence from FSRQs to BL Lacs with FR I BL Lacs at the end of this sequence.

关键词： accretion black hole physics BL Laceratae objects:general galaxies:nuclei quasars:general

A puzzle of the radio-quiet quasar PG 1407+2.5:Are optical and X-ray emissions produced from a relativistic jet?

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Science China(Physics,Mechanics & Astronomy) 2011年第1期54卷 183-186页

作者： CHEN Liang 1,2.3 & BAI JinMing 1,2.1 National Astronomical observatories/yunnan {2.,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 1. National Astronomical observatories/yunnan {2. Chinese Academy of Sciences Kunming 650011 China2. Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

PG 1407+2.5 is a radio quiet quasar that has a relativistic *** this report,we show some peculiar properties of its optical and X-ray emissions,which indicate possible non-thermal origins produced from the *** use a simple synchrotron + synchrotron self Compton (SSC) model to fit the emissions with different ratios of energy densities between the magnetic field and electrons (η≡U B/U e),which predicts a different γ-ray *** First LAT AGN Catalog (1LAC) did not include PG 1407+2.5,which indicates an upper limit of γ-ray *** upper limit constrains the ratio to be unreasonably large (η≥10 4-5).This inversely indicates that the optical and X-ray emissions may not be produced from the beaming *** discuss the physical implications of these results.

关键词： active galactic nuclei jet non-thermal emission PG 1407+2.5