准噶尔盆地南缘侏罗系碎屑成分特征及其对构造属性、盆山格局的指示意义

砂岩碎屑成分分析是进行沉积物源岩石类型、构造属性和盆山演化分析的重要途径。准噶尔盆地南缘侏罗系物源构造属性以“再旋回造山带”、“弧造山带”和部分“岩浆弧”物源为特征,物源岩石类型主要为中酸性岩浆岩、变质岩和沉积岩,岩石成分、重矿物含量及其组合显示东、西剖面在物源上存在一定差异。天山内部侏罗系物源构造属性以“再旋回造山带”、“混合造山带”为主,物源岩石类型主要为中酸性岩浆岩和变质岩,但各剖面的岩石成分、重矿物组合特征及相对含量差异较大。综合天山内部与准噶尔盆地南缘野外剖面沉积特征、岩屑成分及钻井岩心分析表明,天山地区早、中侏罗世盆山格局以盆地沉积范围大、天山正地形较小为特征,不存在地理分割明显的天山山脉,侏罗纪盆地南缘至少存在三个物源体系(西准噶尔山、克拉麦里山和(古)天山);晚侏罗世一早白垩世早期,岩石成分成熟度偏低,砾岩等粗碎屑沉积明显增多,同时不稳定重矿物及其组合稍有增加可能与晚侏罗世天山构造格局分异、构造活动相对活跃有关,天山山脉明显隆升并造就天山南北沉积环境的巨大差异。     

Closed magnetic structures in the chromosphere and in the transition region

Using simultaneous observations of the same solar regions in the lines H and Civ 1548 Å, we have derived schematic models of closed magnetic lines from dynamical constraints. We conclude that the magnetic loops are closed at higher levels above facular than above non-facular regions. This result remains valid whatever are the assumed density models and even if we take into account the 3 min oscillations. The center-to-limb behaviour is well predicted by taking into account the relative opacity in chromosphere and transition region.     

Dynamical fine structure of a quiescent prominence

A quiescent prominence has been observed with the MSDP spectrograph at the Pic du Midi Observatory. H profiles are obtained simultaneously in a 2D field, allowing a statistical analysis. The standard deviations of Doppler shifts and line widths are investigated as functions of the line intensity. The observations are compared with numerical simulations assuming that the prominence is made of identical threads, the velocity of which is distributed according to gaussian functions. The processing of simulations is very close to the processing of observations. The mixing by seeing effects and the transfer of radiation across several threads along the line of sight are considered. The results are consistent with the values derived by Engvold et al. (1989) and Zirker and Koutchmy (1989, 1990, 1991).The best fits are obtained with the following conditions. The temperature is 8500 K. In the middle range of intensities, each pixel results typically from the mixing of 6 velocity threads, the optical thickness of which is roughly 0.2 at H center, and the geometrical thickness larger than 1000 km. It is likely that the velocity threads have larger sizes than the density threads. The fit of the results is improved by taking into account a slight scatter of source functions throughout the prominence.In the central parts of the prominence, the fit is obtained by assuming that the line-of-sight velocities of the threads have a gaussian probability function (standard deviation 7 km s^–1).In the edges, we suggest larger scatter of velocities, and two combined dispersions. The velocity threads observed along a given line of sight are supposed to have neighbouring velocities (dispersion 7 km s^–1) around a mean value taken at random inside another distribution function (dispersion 7 km s^–1).     

Dynamical fine structure of a quiescent filament

A quiescent filament was observed near the center of the disk (N5, W5) with the MSDP spectrograph of the 50 cm refractor of the Pic-du-Midi Observatory on June 17, 1986. We focus our study on the statistical moments of the Dopplershift,V ₁, and the intensity,I ₁, at the center of a chord of the Hα profile (±0.256 Å), versus the minimum intensityI ₀. We use a statistical model simulating a numbern _max of threads (of optical thicknessτ ₀ and source functionS ₀), seen over the chromosphere. The threadsj along the same line-of-sighti are identical except for the velocityv _j (gaussian distributionv ₀,σ _v). We search for the best fit between the observed and simulated quantities:V ₁,σ (V ₁),I ₁,σ(I ₁), and the histogram of theI ₀ values over the field of view. A good fit is obtained with: (a) threads characterized byτ ₀ = 0.2,S ₀ = 0.06 (unit of the continuum at disk center), mean upward velocityv ₀ = 1.7 km s⁻¹ and gaussian-type velocity distributionσ _v = 3.5 km s⁻¹. Other possible values ofτ ₀ andσ _v are discussed; (b) underlying chromosphere deduced from observed quiet Sun (outside the filament) by modifying the chromospheric velocities: additional mean upward velocity 0.7 km s⁻¹, standard deviation reduced by a factorF _c ∼ 0.7. The results are discussed in connection with the values deduced from prominence observations.     

Wave reflections in the solar atmosphere

The small phase-lag between velocities observed at different chromospheric levels is interpreted as being due to acoustic waves reflected by the very hot atmospheric layers of the chromosphere-corona transition zone. We consider first an isothermal slab, then a realistic solar atmospheric model and calculate weighting functions for velocities in Ca ii lines. It is shown that taking into account these functions and integrating over horizontal wave numbers leads to a good agreement with previous observations (Mein, 1977) in the case of 8498 and 8542 Ca ii lines. For the K line, the less good agreement shows that magnetoacoustic waves become important in the upper chromospheric layers.     

Ejection of chromospheric material associated with injection of electrons in the solar corona

Observations of a type III radio event and of concurrent H absorbing features are related. They were obtained with the Nançay Radioheliograph and the Multichannel Subtractive Double Pass spectrograph operating in H at Meudon. We are looking for the signature at chromosphere levels of the acceleration of the elctron beams triggering the type III bursts. Some promising results are pointed out: the relationship between velocities in H and the occurrence of the type III bursts, the shape of H line which reveals turbulent motions, the presence of parasitic magnetic polarity and the probable existence of a shock wave. A schematic scenario of the phenomenon is proposed, taking into account the observational constraints.     

Filament channel structures in a Si iv line related to a 3d magnetic model

A recent 3D magnetic model of filament support (Aulanier and Démoulin, 1998) has shown that specific morphologies derived from the model, based on SOHO/MDI magnetograms, match quite well with the observations of a filament observed in H and Caii lines with the German telescope VTT in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some predictions of this model concern the filament channel. To continue the comparison of model and data, we have investigated the same filament region observed in ultraviolet by the SOHO spectrometers SUMER and CDS. The elongated EUV fine structures in the filament channel observed in the Siiv 1393.76 Å line by SUMER have similar orientations and locations to features predicted by the model of Aulanier et al. (1999a). These regions are near the bases of field lines which tangentially join to the photosphere in so called 'bald patches' and are parts of large arcades above the filament channel. In addition, we consider the Siiv Doppler shifts in these structures and compare them to what might be expected from the model field structure. Our study also suggests that the filament has a very low opacity in Siiv, lower than that of the Ov line observed by CDS.     

近20年来长江三角洲海岸带典型区土地利用变化与生态环境效应研究

【研究目的】近20年来,长江三角洲海岸带地区土地类型结构发生显著转化,海岸带开发与保护的矛盾凸显。本文旨在开展长江三角洲海岸带典型区土地利用变化与生态环境效应研究,为海岸带地区的土地资源可持续利用、海岸带环境保护提供科学依据。【研究方法】利用美国Landsat卫星系列遥感影像和中国资源卫星系列遥感影像,采用自动监督分类并结合目视解译,获取了研究区1995—2015年共5期土地利用分类数据,分析土地利用变化特征和趋势,探讨长江三角洲海岸带典型区城镇发展、围填海时空变化及生态环境效应。【研究结果】长江三角洲海岸带典型区（南通、上海、嘉兴、宁波和舟山）1995年至2015年,土地利用变化明显,耕地大幅度减少,比例从1995年的68.8%降为2015年的55.7%;城镇建设用地迅速扩张,年平均增加192.8 km²。【结论】在快速城市化过程中,人口、单位面积能源消耗等快速增加,环境问题凸显,大量的耕地转为建设用地,围填海使滨海湿地面积快速减小和消失,导致CO₂和污染物释放与吸收严重失衡,海洋环境受流域和沿海城镇化建设的影响明显,长江口及邻近海域近20年来赤潮频发,研究区陆域和海洋环境压力增加。创新点：选取长江三角洲海岸带典型区,首次以1995—2015年5期序列遥感影像数据为基础,采用空间叠加分析方法,着重分析了建设用地和围填海区域的时空演化特征;以人类活动为主线,综合多种海洋环境指标,分析快速城市化进程中,建设用地和围填海导致的生态环境效应。     

海洋测深中垂直分置海底混响信号的仿真分析

海洋测深中,海底混响信号是测深仪回波信号检测的主要内容。测深仪通常采用信号的相关处理方法对其进行检测,因此在设计测深仪的回波处理单元时,系统地分析海底混响信号的相关特性就显得尤为重要,对混响信号仿真是分析其特性的有效手段。基于单元散射理论,依据海底散射系数的空间相关半径划分散射单元,给出垂直分置海底混响信号的仿真方法。研究结果表明,该模型物理意义明确,计算简单。仿真得到的海底混响信号具有非常好的空间相关性和时间自相关性,与实测的海底混响信号相符,可用于对混响场特性的分析,改善测深仪的设计,从而有效提高测深仪的测量精度。     

Structure and evolution of velocities in quiescent filaments

Simultaneous observations of radial velocities in a quiescent prominence seen in H on the disk and in the underlaying photosphere have been obtained in the Meudon Observatory: Doppler shifts in photospheric lines are weaker than in the surrounding regions (<0.3 km s^-1); the scale of velocity structures is smaller (<10⁴ km). The vertical component of velocities cannot be neglected. H Doppler shifts show that: (a) Highest velocities are often correlated with high brightness horizontal gradients, which suggests that filament and surrounding bright regions belong to the same geometrical and dynamical structure. (b) Fast motions (7 km s^-1) have short life-times (a few minutes). (c) Slow motions in dark regions (<3 km s^-1) are associated with blue shifts and may last several hours. This behaviour was confirmed in many other cases by filament observations with the 3-wavelength H patrol. This is consistent with EUV observations of the transition zone around prominences, but disagrees with downward motions as seen at the limb, unless these motions do not refer to material velocities.