Semi-empirical models of the white-light flare on October 24, 1991

On October 24, 1991, a white-light flare was observed both from space and from the ground. A multi-waveband spectral analysis shows that the peak time of the continuum emission coincides well with that of a radio burst at 2840 MHz and with the hard X-ray emission. Three semi-empirical models, corresponding to the pre-flare condition and to the peak time of continuum emission both with and without non-thermal excitation and ionization of hydrogen by an electron beam, have been obtained. The results indicate that there is fast heating both in the chromosphere and the photosphere. Some evidence is given that this WLF is very likely a result of bombardment by an electron beam. By taking into account non-thermal effects, the chromospheric temperature of the semi-empirical model is significantly reduced.     

A modified land surface temperature split window retrieval algorithm and its applications over China

Due to the difficulties in correcting the influences of the atmosphere absorbability and the Earth surface emissivity diversification, the retrieval of LST (land surface temperature) from satellite data is a challenging task. In this paper, a modified Becker's split window LST inversion algorithm is developed for retrieving LST from the NOAA-16/17 AVHRR data. A new set of parameters for Becker's LST algorithm is proposed. The algorithm is developed from a surface brightness temperature dataset generated from the MODTRAN program, which uses a range of surface parameters and atmospheric quantities as inputs. The 10-day composites of the channels 4 and 5 brightness temperature data of NOAA-17 AVHRR (1-km resolution) are used to generate the clear-sky LST. As a validation of the algorithm, the retrieved LST is compared with MODIS LST of same period and area. The two LST products are found to be consistent, with the absolute difference being about 2.5 K for most areas. The NOAA retrieved LST is also compared with in-situ ground surface 0-cm measurements taken from 257 meteorological stations, which cover overall China area for the three periods of satellite observations. The comparison shows that the correlation between the retrieved LST and in-situ measurements is over 0.90 and the RMSE (root mean square error) is about 3.4 K.     

IAG2001年科学大会与大地测量学的最新进展

扼要报导了国际大地测量学术界的一次重要会议－IAG2001年科学大会。根据会议的学术报告，对坐标系统的统一与协调，全球重力场研究，导航卫星的应用，地壳形变与地球动力学等方面的研究进展作了详细介绍。     

Catastrophe of Coronal Magnetic Flux Ropes Caused by Photospheric Motions

Using a 2.5-D, time-dependent ideal MHD model in Cartesian coordinates, we carried out numerical simulations to investigate the equilibrium and evolution properties of a magnetic configuration that consists of a coronal magnetic flux rope and a partly open photospheric background field, which is equivalent to that produced by a two-patch magnetic source on the photospheric surface. The axial and annular magnetic fluxes of the flux rope are given and fixed. The global magnetic configuration evolves in response to three types of changes of the background field: decreasing of the distance between the two sources, shrinking of the size of each source, and increasing of the shear in the closed component of the background field. As a result, the geometrical parameters of the flux rope, i.e. the height of the rope axis, the half-width of the rope and the length of the vertical current sheet below the rope, change due to the variation of the background field. It is shown that for a given coronal magnetic flux rope in a partly open background field, the variation of the geometrical parameters of the flux rope displays a catastrophic behavior, namely, there exists a critical point for each case, at which an infinitesimal change of the background field leads to a loss of equilibrium, and thus a jump of the flux rope. The implication of such a catastrophe in solar active phenomena is briefly discussed.     

浙江中生代浅成热液金银成矿作用的耗散结构模型

浙江中生代主要浅成热液金银矿床在蚀变-矿化过程中的一些物理化学特征参数(如T、P、St和ρ等)呈非线性的变化关系,其控制变量是P、T和PH值.推断条带(或环带)状构造的矿脉(石)是由减压沸腾作用造成的.据Drummond等(1985)沸腾的模拟计算和研究表明,[H+]浓度是决定沸腾热液中的Au、Ag等成矿元素命运的主要因素.因此,可以[H+]浓度(状态变量)作为序参量来反映成矿溶液中Au、Ag浓度的变化趋势;并建立其自组织过程的动力学方程与开放沸腾热液系统Au、Ag沉淀的耗散结构模型.     

Optical Identifications of X—ray Selected AGNs

During the ROSAT All-Sky Survey (RASS; Voges 1992, 1997) about 80,000 X-ray sourceswith a detection likelihood 2 10 were detected, from which 18,811 sources having a PSPC countrate larger than 0.05 ets s--1 and detection likelihood 3 15 were compiled in the RASS-BSC(VOges et al. 1996a). More than 65% RASS sources remain unidentified (Voges et al. 1996b).The optical spectroscopic study of these RASS sources is essential for understanding them moreclearly.The idelltification of X-…     

类星体红移分布△ln（1＋z）＝0．205周期性的一种解释

根据红移定义１＋ｚ＝λｉ／λ０ｉ，我们认为类星体红移分布ｌｎ（１＋ｚ）周期性受两个因素影响。首先，决定类星体红移的主要线（如Ｌα１２１６，ＣＩＶ１５４９，ＣＩＩＩ１９０９，ＭｇＩＩ２７９８，ＮｅＶ３４２６，ＯＩＩ３７２７，ＮｅＩＩＩ３８６８，Ｈγ４３４０，Ｈβ４８６１，ＯＩＩＩ５００７）固有波长可能构成０．２０５的周期性；另外，这些谱线的观测波长进入一定光学窗口对红移有一定限制，在一定条件下，它正好在某些红移出现峰值，并与ｌｎ（１＋ｚ）＝０．２０５预言峰值一致。我们还在这两个基本考虑下进行模拟取样，发现有明显周期性，定量上证实了我们的基本考虑。本文是类星体红移分布的一种解释，它能说明为什么统计分布不同样品能得到不同的结论。进而，我们认为红移分布周期性不能成为内禀红移观点的观测支持。     

SEA LEVEL RISE OF THE ZHUJIANG RIVER DELTA AND NEOTECTONICS

A linear regression analysis of 28 selected tide-gauge stations of the Zhujiang Estuary shows that there has been a tendency of local sea level rise at a rate of 2.028 mm per year. The origin of the variation is significantly attributed to the local tectonic movement of discrepant fault-block. Based on this, four types of relative local sea level changes are classified. According to calculation, half of the fertile land, or 800 km2 of the delta plain will have been submerged by sea water by about 2040. This will yield a significant influence on the economic construction and human activities.     

A Two-Dimensional Alfvén-Wave-Driven Solar Wind Model

This paper presents a two-dimensional, Alfvén-wave-driven solar wind model, in which the wave energy is assumed to cascade from the low-frequency Alfvén waves to high-frequency ion cyclotron waves and to be transferred to the solar wind protons by cyclotron resonance at the Kolmogorov rate. A typical structure in the meridional plane consisting of a coronal streamer near the Sun, a fast wind in high latitudes, and a slow wind across the heliospheric current sheet, is found. The fast wind obtained in the polar region is essentially similar to that derived by previous one-dimensional flow-tube models, and its density profile in the vicinity of the Sun roughly matches relevant observations. The proton conditions at 1 AU are also consistent with observations for both the fast and slow winds. The Alfvén waves appear in the fast- and slow-wind regions simultaneously and have comparable amplitudes, which agrees with Helios observations. The acceleration and heating of the solar wind by the Alfvén waves are found to occur mainly in the near-Sun region. It is demonstrated in terms of one-dimensional calculations that the distinct properties of the fast and slow winds are mainly attributed to different geometries of the flow tubes associated with the two sorts of winds. In addition, the 2-D and 1-D simulations give essentially the same results for both the fast and the slow winds.     

奎先达坂考察报告

作者于１９９５年９月对新疆天山南坡的奎先达坂进行考察，记述了考察的印象并对下一步的视宁度观测提出了具体建议。