流星雨摄影观测记录的罕见现象

2001年狮子座流星雨,是几百年来难得有机会在中国观测到的一场流星暴。在我们收集到的照相观测资料中,发现了一些特殊的、还未引起广泛注意的流星现象。"蛇行"的流星以及螺旋形并带有辐条结构的流星余迹,早在我国古代记录中就可以找到印证。现代的照相技术,不仅直观地显示了文字难以描述的颜色、形态和变化,而且提供了可永久性进行测量的记录。其中包括罕见的对流星余迹的双站观测资料。用常规的"高空风作用"难以解释这些观测现象。它们可能反映了流星带电体与地球磁场的相互作用。     

流星雨双站观测的预备计算

本文叙述了流星雨双站观测预备计算的原理,这些原理自1987年以来已在实践中应用。     

昭平、惜福和哈密铁陨石的矿物岩石学研究和化学群分类

详细分析了中国新近发现的3块铁陨石即：昭平、惜福和哈密的矿物组成和化学成分，并根据它们的化学元素（Ga、Ge、Ni和Ir等）含量进行了分群；昭平和惜福铁陨石分别属于IAB的低Ni低Au亚群和ⅢCD铁陨石群，哈密铁陨石因为其本身的Ga和Ge的含量很低以及实验仪器的精度限制，只能得知该陨石的Ga含量小于2ppm、Ge含量小于10ppm，根据其化学元素含量、结构特征和矿物组成，初步判断哈密铁陨石应属于未分群铁陨石．     

论在空间灾害性天气条件下低频太阳射电观测在预警心脑血管事件中的作用

太阳活动是对地球及人类生活影响最直接的天文活动,在航空航天、通信、电力以及人体健康方面影响着人类的生产生活。通过以往的一些研究结果分析非光学(non-optical)范畴的太阳活动例如日冕物质抛射、太阳射电爆发与某些人类疾病呈正相关性,这与低频太阳活动对日地空间的影响有密切联系。采用云南天文台2012年上半年70 MHz~1 500 MHz波段观测数据与昆明医科大学第一附属医院心脑血管病例结合进行相关分析,得到利用低频太阳活动爆发对人体影响预警的时间延迟因子(与等离子体抛射物质到达地球有关)。通过研究证明利用直接太阳低频射电观测数据能够较之于之前国际上利用宇宙线的福布希下降进行的空间天气预警提前2~3 d,有效地提高了预警效果,为下一步基于低频空间异动观测数据现报——健康实时预警系统的建立打下了工作基础。     

恒星尘埃的实验室研究--实验天体物理学

原始球粒陨石含有来自恒星的微小固体颗粒(微米级),这些尘埃的同位素组成与太阳系物质截然不同,它们是目前唯一能直接获得的恒星固体样品．已发现的恒星尘埃有金刚石、石墨、碳化硅、刚玉、尖晶石、氮化物、和硅酸盐等,它们的母体恒星包括红巨星,AGB恒星、新星和超新星．对恒星尘埃的研究,使得更深入地了解星系的化学演化历史、恒星内部的核反应和湍流机制、恒星大气中尘埃的形成、星际介质物理现象等．恒星尘埃把天体物理领域延伸到了微观世界,它有机地结合了地球化学实验技术和天体物理理论,开辟了一门崭新的天文学分支实验天体物理学．     

强X射线事件与太阳黑子群的McIntosh分类及形态快速变化

本文对1981.7.1—1982.12.31的强硬X射线事件(peak rate of the count≥1000),太阳黑子群的McIntosh分类及黑子形态的快速变化作了统计。分析了它们之间的关系。文中将最大黑子型别为K的13种McIntosh分类作为强X射线爆发的判据,可捕捉到63％的强X射线事件,其报准率为24％,虚报率为76％。若把既有形态快速变化又存在K结构的黑子群作为预报判据,则报准率可升至60％,虚报率可降至40％,与前者比较虚报率下降80％左右。     

北京天文台对FFS事件的观测研究

从观测手段和取得的资料两个方面,评价了两个太阳峰年中北京天文台所观测到的太阳射电爆发中毫秒级快速精细结构（FFS）的观测结果．估计了新的观测仪器在第23周峰年将取得的观测结果．也讨论了在观测研究中值得重视的一些问题．     

太阳的空间观测与研究Ι—太阳电磁波 辐射的观测与研究概况

太阳空间观测为揭示太阳新的观测现象与研究开拓了新的途径。空间观测具有全波段、全时段、全方位以及无大气抖动和大气散射光等观测优点。本文着重探讨了太阳空间长波射电观测、Ｘ射线观测、紫外线观测的成就与研究结果。这些波段（包括光学）的爆发均起因于太阳大气中被加速的荷能电子与太阳等离子体、磁场相互作用而产生的电磁辐射,其能量约占太阳耀斑总量的１／４,即１０２５Ｊ。     

Observation and Research on Strong Meteor Showers and Their Catastrophic Space Weather Events

During the first international joint observation of the Leo strong meteor shower, multidisciplinary and multi-media synthetic observation of Leo and Draco strong meteor showers and their catastrophic space weather events were carried out. The comprehensive analysis of the observed and related data of the Leo, Perseus and Draco strong meteor showers obtained for near half a century (from 1957 to 2003) fully verifies that the non-sporadic periodic strong meteor shower may lead to catastrophic space weather events. Preliminary identification is made of the following: the mechanism of formation of strong meteor showers, the law of occurrence of the f_bE_s abnormal peak and serious safety hazards for astronavigation. Also discussed in this paper are the evolutionary process of cometary dust, the law of occurrence and loss of cosmic dust storm and the mechanism of maintaining cosmic dust in the mid-latitude E_s layer.     

1998～2000年狮子座流星雨的预报和观测

"1998年狮子座流星雨可能是暴雨,最佳观测地在东亚"的预报,客观上加速了中国对流星雨的现代研究。几年来,对狮子座流星雨的观测和研究,是在全国狮子座流星雨联测小组的组织和领导下发展起来的。这包括使用目视方法、照相方法和无线电方法的观测,以及组织广大天文爱好者在全国范围内的观测。我们的确也观测到了很多重要的现象,如流星雨的纤维结构、尺度分布和质量密度分布的变化等等。我们发展了数据处理方法,将处理其它天文观测数据的"时间窗"方法移植到了流星雨的数据处理中。这一方法如今在流星雨研究中已经在世界上普遍使用了。我们还提出了流星雨的质量流参量ZHMR,它对于今后流星雨的观测比较和预报可能更加有用。在雷达观测方面,我们观测到了1998年所期待的流星雨强度主峰。在此主峰过了大约18h之后,又观测到了地球电离层的反常爆发。从1998年连续两天狮子座流星雨不同的表现,以及从全国不同地区的观测得到的流星质量分布系数的差异,我们提出了大、小2种不同粒子的混合流模型,很好地解释了观测到的现象。从天体力学的基本公式出发,我们发现流星群轨道升交点和其母彗星轨道升交点之差,不仅与当时的抛射速度,而且与彗星抛出这些尘埃粒子时在轨道上的位置有关。对于1998年的观测,最可能的是这些粒子是     

The Canadian Meteor Orbit Radar: system overview and preliminary results

This paper describes the Canadian Meteor Orbit Radar (CMOR) that has been in operation since late 2001. CMOR is a 3 station meteor radar operating at a frequency of 29.85 MHz near Tavistock, Ont. To avoid bias against fragmenting meteoroids that is inherent in the traditional multi-station method of Gill and Davies (Mon. Not. R Astron. Soc. 116 (1955) 105), we use a completely geometrical method similar to that used in the AMOR system (Quart. J. R. Astron. Soc. 35 (1994) 293) based on the interferometric determination of the echo directions and the time delays of echoes from two remote stations to obtain the trajectories and speeds of meteoroids. We describe the hardware and some of the software and present some preliminary results that provide a good indication of present capabilities of the system. Typically, we can measure 1500 individual trajectories, and hence orbits, per day with a mean accuracy of 6° in direction and about 10% in speed. A small subset of these for which it is possible to measure the speeds using Hocking's (Radio. Sci. 35 (2000) 1205) method yield speeds with a precision of about 5%. The purpose of this paper is to show that the radiants and speeds necessary for the computation of orbits are well measured rather than to discuss any orbital surveys.     

Activity Profile of the Sextantid Meteor Shower

The detailed activity profile of the Sextandids - one of the day-time meteor showers - is poorly known and still unclear. Using the forward-scatter radio technique we have successfully been able to obtain further detailed overall activity profile of the Sextantids for seven consecutive years: 1991–1997. Analysis confirmed the Sextantid activity duration in solar longitude (J2000) of at least 184–193° and the maximum solar longitude at 188.35 ± 0.10° with a full width at half maximum (FWHM) of 2.0 ± 0.2°. Performing the numerical integrations, we also substantiated a possibility of the association between Apollo-type asteroid (3200) Phaethon and the Sextantids. Furthermore, we roughly estimated relative maximum flux rate of Sextantids : Geminids as 1 : 3 amplitude ratio. Depending upon the flux rates and the time lags of the orbital evolution with Phaethon, we conclude that the Sextantids are at a more progressive stage of orbital evolution than the Geminids if both meteor streams are really associated with Phaethon. This revised version was published online in July 2006 with corrections to the Cover Date.     

IAU Meteor Database of photographic orbits – version 2003

The IAU Meteor Data Center in Lund has acted as a central depository for meteor orbits obtained by photographic, video and radar techniques. The database of precisely reduced photographic meteors contains data on 4581 meteor orbits obtained by 17 different stations or groups in the period 1936–1996. The orbital and geophysical data are available in two separate files as well as in an alternative file with the merged data. In various studies of meteoroid streams as well as in studies of the sporadic meteor background, it is often necessary to utilize both the orbital and the geophysical data files. Since the database is a compilation of partial, not perfectly compatible catalogues from many observing stations, the merging of parameters from one data set to another may sometimes present problems. The present contribution is a note on some problems encountered in the merging procedure. Moreover, it is evident that the database includes a small amount of erroneous data – either in the observations or in the subsequent data reductions. The latter error is not surprising in view of the lack of modern computers at several stations in the past. A final, corrected version of the IAU MDC Lund photographic meteor orbits (eq. 2000.0) can now be requested through the homepage of the Astronomical Institute, Slovak Academy of Sciences (http://www.astro.sk/~ne/IAUMDC/Ph2003/database.html).     

Possible Detection of GEMINID 2007 Meteor Shower During Day-Time from VLF Radiation Spectra

The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiation spectra in Tripura (23.50° N, 91.25° E), India, is presented here. The field experiments were performed during 12–17th December, 2007 inside Tripura University campus located at a hilly place in the North-Eastern part of India. A well calibrated software VLF receiver was used to perform the field experiments. Analyses of data reveal an hourly average rate of the shower around 50. The VLF emissions lie in the range from 8 kHz to 13 kHz which is 10 to 15 times higher than previous reports. The mean duration of each VLF emission calculated from dynamic spectra is found to be 6 s and the mean bandwidth is 3.6 kHz. The temporal variation of VLF emission duration and bandwidth of VLF radiation is also studied. The results strongly support the fact that VLF electromagnetic waves are produced during the passage of meteors in the atmosphere. The experiment also makes the study of dynamic VLF spectra as a strong tool to detect low intensity meteor shower during daytime.     

March 1, 2005 Daylight Fireball Over Galicia (NW of Spain) and Minho (N. Portugal)

A daylight bolide was observed over Galicia (NW Spain) and Minho (N. Portugal) on March 1, 2005 at 15 h10 min ± 3 min UTC. We interviewed 23 eyewitnesses of the event in order to obtain the azimuth, altitude, and slope of the fireball’s trajectory. Reports suggest an atmospheric ending height below 20 km, indicating that meteorite survival was likely. From the reconstructed trajectory and the fireball’s duration, we obtained the approximate heliocentric orbits for the meteoroid. Assuming an entry velocity higher than 20 km s⁻¹ which is consistent with its estimated duration, the meteoroid originated in the asteroid belt.     

Prospects for meteor shower activity in the venusian atmosphere

We investigate the possibility of detectable meteor shower activity in the atmosphere of Venus. We compare the Venus-approaching population of known periodic comets, suspected cometary asteroids and meteor streams with that of the Earth. We find that a similar number of Halley-type comets but a substantially lesser population of Jupiter family comets approach Venus. Parent bodies of prominent meteor showers that might occur at Venus have been determined based on minimum orbital distance. These are: Comets 1P/Halley, parent of the η Aquarid and Orionid streams at the Earth; 45P/Honda-Mrkos-Pajdusakova which currently approaches the venusian orbit to 0.0016 AU; three Halley-type comets (12P/Pons-Brooks, 27P/Crommelin and 122P/de Vico), all intercepting the planet's orbit within a 5-day arc in solar longitude; and Asteroid (3200) Phaethon, parent of the December Geminids at the Earth. In addition, several minor streams and a number of cometary asteroid orbits are found to approach the orbit of Venus sufficiently close to raise the possibility of some activity at that planet. Using an analytical approach described in Adolfsson et al. (Icarus 119 (1996) 144) we show that venusian meteors would be as bright or up to 2 magnitudes brighter than their Earth counterparts and reach maximum luminosity at an altitude range of 100-120, 20-30 km higher than at the Earth, in a predominantly clear region of the atmosphere. We discuss the feasibility of observing venusian showers based on current capabilities and conclude that a downward-looking Venus-orbiting meteor detector would be more suitable for these purposes than Earth-based monitoring. The former would detect a shower of an equivalent Zenithal Hourly Rate of at least several tens of meteors.     

A technique for calculating meteor plasma density and meteoroid mass from radar head echo scattering

Large-aperture radars detect the high-density plasma that forms in the vicinity of a meteoroid and moves approximately at its velocity; reflections from these plasmas are called head echoes. To determine the head plasma density and configuration, we model the interaction of a radar wave with the plasma without using assumptions about plasma density. This paper presents a scattering method that enables us to convert measurements of radar cross-section (RCS) from a head echo into plasma density by applying a spherical scattering model. We use three methods to validate our model. First, we compare the maximum plasma densities determined from the spherical solution using 30 head echoes detected simultaneously at VHF and UHF. Second, we use a head echo detected simultaneously at VHF, UHF and L-band to compare plasma densities at all frequencies. Finally, we apply our spherical solution to 723 VHF head echoes and calculate plasma density, line density and meteoroid mass in order to compare these values with those obtained from a meteoroid ablation and ionization model. In all three comparisons, our results show that the spherical solution produces consistent results across a wide frequency range and agrees well with the single-body ablation model.     

TV Observation of the Daytime Meteor Shower; The Arietids

We have carried out multi-station TV observations since 1994 in order to determine the orbit of the Arietid daytime meteor stream. In 1999, one possible Arietid meteor was recorded by our simultaneous observations and its orbit was determined. In 2003, two Arietid meteors were observed from two stations of our observing site, those orbits were determined precisely, the orbital elements were in good agreement with each other. This is the first time that determination of the precise orbit of the Arietids has been made from optical observations. The orbit of these Arietid meteors, and comparison with the orbit obtained from radar observations are discussed.