Comparative Planetary Space Physics     

Wei Yong  Rong Zhaojin  Zhong Jun  Chai Lihui  Yue Xin&#x  an  Liu Libo  Yu Sheng  Zhu Rixiang  Wan Weixing 《地球科学进展》2017,32(1):15-20

It has been 60 years since the space physics as new branch of geophysics started to grow in 1957 when the space age was opened by a small satellite called sputnik. The knowledge of Earth and planetary space has been significantly extended and deepened, but the questions we are facing today are more challenging. A consensus reached is that we have to regard the Earth (planet) as an integrated system including all spheres from the inner core to the magnetosphere, and we should try to investigate some questions standing on the ground of interdisciplinary study, especially those questions related to Earth’s (planetary) evolution. Space environment as the outer part of a planetary system, commonly exists in all planets but also exhibits strong diversity. Here, we introduce the short history of basic ideas and methods of comparative study, the advantages on understanding of some issues of global scale, and the prospect from comparative perspective.  相似文献   

Natural oligotrophy vs. pollution-induced eutrophy on the SE Mediterranean shallow shelf (Israel): Environmental parameters and benthic foraminifera     

Orit Hyams-Kaphzan  Ahuva Almogi-Labin  Chaim Benjamini  Barak Herut 《Marine pollution bulletin》2009,58(12):1888-1902

The eastern Mediterranean is naturally highly oligotrophic, but urbanization along the Levant coast has led to raised organic and nutrient loads. This study tracks living foraminiferal assemblages at two sites near an activated sewage sludge outfall from 11/2003 to 5/2004. Oligotrophic site PL29 shows seasonal variations in O_2, chlorophyll a, and organic carbon, and has an abundant, diverse benthic foraminiferal assemblage living at various in-sediment depths. At eutrophic site PL3, ∼16 years of sludge injection favor a depleted assemblage primarily of opportunist foraminifera. This site shows less seasonality, is subjected to organic matter overload, O₂-stress, and periodic anoxia, foraminifera are less abundant and diverse, and live at shallower depths. The assemblages at both sites represent a common pool of species, with Ammonia tepida highly dominant. Benthic foraminifera were therefore found to be sensitive to trophic trajectories, respond on sub-seasonal time-scales, and track injection and dispersal of organic loads on the shelf.  相似文献   

真鲷饵料生物褶皱臂尾轮虫和眼点拟微绿藻的大量培养     

刘新富  雷霁霖  刘忠强  柳学周 《海洋科学》2000,24(5):47-51

于1992～1994年 ,在中国水科院黄海水产研究所小麦岛试验基地(青岛)进行的“中日合作真鲷增殖放流项目”执行期间 ,对真鲷饵料生物———眼点拟微绿藻 (Nannochloropsisoculata)和L型褶皱臂尾轮虫 (Branchionus plicatilis)进行了大量培养。眼点拟微绿藻的平均接种密度为1211.3×104个/ml,经5～6d的室内或室外露天培养即可达到平均为2341.0×104 个/ml的收获密度 ;采用眼点拟微绿藻和新鲜面包酵母作为混合饵料 ;褶皱臂尾轮虫 (L型 )培养3～4d即可由接种时平均密度148.0个/ml,增长至平均216.8个/ml的采收密度。眼点拟微绿藻和轮虫的日间增殖密度分别是12.8 %和26.6 %。每生产108个褶皱臂尾轮虫需要消耗0.73m3眼点拟微绿藻 (密度为2000×104/ml)和790.8g 鲜面包酵母。采用此法 ,作者连续3a成功地为每年百万尾以上真鲷苗种提供了足够的生物饵料。总结3a苗种培育和生物饵料培养之间的关系 ,作者认为 ,大规模稳定生产海水鱼类苗种时,育苗与饵料生物培养 (褶皱臂尾轮虫和眼点拟微绿藻 )水体的合理比例应为1∶1～1.5∶3。  相似文献   

基础设施与人类生存环境之关系研究   总被引：18，自引：4，他引：18  

金凤君 《地理科学进展》2001,20(3):276-285

人类在其发展中倾注了大量的人力、物车、财力建设基础设施，希图构筑理想生存环境。但基础设施为人类带来了什么？对人类的发展产生了何种影响？如何认识基础设施在人类生存环境演化中的作用？本文从积极角度阐述了基础设施与人类生存环境之关系，透视了基础设施在活动空间扩展、资源共享和生存环境优化方面的作用与意义。  相似文献   

湖南中部中泥盆世的轮藻化石及其生活环境探讨     

曾德敏  胡济民 《湖南地质》2001,20(2):89-91,97

湖南中部长沙、宁乡、益阳、安化、涟源、邵东等县，中泥盆统跳马涧组和棋子桥组产丰富的轮藻化石，以宁乡县崔坪峡塘剖面为代表，有3属7种1型1新种，并首次发现了轮藻植物节部化石，建立了2个化石带：（1）Trochiliscus ingricus-Eochara changshaensis组合带，分布在跳马涧组，时代为中泥盆世早期；（2）Sycidium顶峰带，分布在棋子桥组，时代为中泥盆世晚期，并对轮藻的生活环境进行了探讨。  相似文献   

Single planet formation regime in the high-ionization environment:Possible origin of hot Jupiters and super-Earths     

Yusuke Imaeda  Toshikazu Ebisuzaki 《地学前缘(英文版)》2018,9(4):1023-1031

We studied the particle growth in a protoplanetary disk in a high-ionization environment and found that icy planet formation is inactive for a disk with an ionization rate 100 times higher than that of the present Solar System. In particular, in the case of M 10~(-7.4)M_☉yr~(-1), only rocky planet formation occurs. In such a case, all the solid materials in the disk drift inward, eventually reach the inner MRI front,and accumulate there. They form a dense, thin sub-disk of solid particles, which undergoes gravitational instability to form rocky planetesimals. The planetesimals rapidly grow into a planet through pebble accretion. Consequently, rocky planets tend to be much larger than planets formed through other regimes(tandem planet formation regime and dispersed planet formation regime), in which icy planet formation actively takes place. These rocky planets may evolve into hot Jupiters if they grow fast enough to the critical core mass of the runaway gas accretion before the dispersal of the disk gas, or they may evolve into super-Earths if the gas dispersed sufficiently early.  相似文献   

太阳绕太阳系质心运动22年周期及其与太阳活动的联系          下载免费PDF全文

刘复刚  王建 《地球物理学报》2014,57(11):3834-3840

对于太阳活动22年周期的成因机制长期存在着争论.本文借助于行星会合指数以及开普勒第三定律,对太阳绕太阳系质心运动周期进行了分析计算.结果发现,太阳绕太阳系质心运动存在22.1826年显著周期,这与太阳磁场变化的22.20年周期相吻合.并从太阳系角动量守恒的角度解释了两者之间的成因联系:在太阳绕太阳系质心运动的准22年周期中,太阳系质心与太阳质心逐步接近而后逐步分离.当两个质心之间的距离接近零的时候,太阳轨道角动量与自转角动量叠加,会导致太阳自转角速度的加快;当两个质心之间的距离逐渐远离的时候,则导致太阳自转角速度的减慢.这可能是引发太阳活动和太阳磁场变化的原因.这一新认识为太阳活动准22年周期成因机制的解释提供了新的线索和依据.  相似文献   

A unified model for hydrogen in the Earth and Moon: No one expects the Theia contribution     

《Chemie der Erde / Geochemistry》2019,79(4):125546

The Moon is thought to have formed after a planetary embryo, known as Theia, collided with the proto-Earth 4.5 billion years ago. This so-called Giant Impact was the last major event during Earth’s accretion, and its effects on the composition of the Earth and the newly forming Moon would be measureable today. Recent work on lunar samples has revealed that the Moon’s water was not lost as a result of this giant impact. Instead, the Moon appears to contain multiple hydrogen reservoirs with diverse deuterium-to-hydrogen (D/H) ratios. For the first time, we incorporate hydrogen isotopic measurements of lunar samples to help constrain the composition of Theia. We show that the Moon incorporated very low-D/H (δD ≈ -750‰) materials that only could have derived from solar nebula H₂ ingassed into the magma ocean of a large (∼0.4 M_E) planetary embryo that was largely devoid of chondritic water. We infer Theia was a very large body comparable in size to the proto-Earth, and was composed almost entirely of enstatite chondrite-like material. These conclusions limit the type of impact to a “merger” model of similarly-sized bodies, or possibly a “hit-and-run” model, and they rule out models that mix isotopes too effectively.  相似文献   

Hurricane damage along natural and hardened estuarine shorelines: Using homeowner experiences to promote nature-based coastal protection     

《Marine Policy》2017

Growing coastal populations, rising sea levels, and likely increases in the frequency of major storm events will intensify coastal vulnerability in coming decades. Decisions regarding how and when to fortify estuarine shorelines against coastal hazards, such as erosion, flooding, and attendant property damages, rest largely in the hands of waterfront-property owners. Traditionally, hard engineered structures (e.g. bulkheads, revetments, seawalls) have been used to protect coastal properties, based on the assumption that these structures are durable and effective at preventing erosion. This study evaluates the validity of these assumptions by merging results from 689 surveys of waterfront-property owners in NC with empirical shoreline damage data collected along estuarine shorelines after Hurricanes Irene (2011) and Arthur (2014). The data show: 1) homeowners perceive bulkheads to be the most durable and effective at preventing erosion, but also the most costly; 2) compared to residents with revetments and natural shorelines, property owners with bulkheads reported double the price to repair hurricane damage to their property and four times the cost for annual shoreline maintenance; 3) 93% of evident post-hurricane shoreline damage was attributable to bulkheads or bulkhead hybrids and a higher proportion of surveyed homeowners with bulkheads reported having property damage from hurricanes; and, 4) shoreline hardening increased by 3.5% from 2011 to 2016 along 39 km of the Outer Banks. These results suggest that bulkheads are not meeting waterfront property-owner expectations despite continued use, and that nature-based coastal protection schemes may be able to more effectively align with homeowner needs.  相似文献   

http://dx.doi.org/10.1016/j.gsf.2016.06.011     

Yusuke Imaeda  Toshikazu Ebisuzaki 《地学前缘(英文版)》2017,8(2):223-231

We present a new united theory of planet formation,which includes magneto-rotational instability(MRl) and porous aggregation of solid particles in a consistent way.We show that the "tandem planet formation" regime is likely to result in solar system-like planetary systems.In the tandem planet formation regime,planetesimals form at two distinct sites:the outer and inner edges of the MRl suppressed region.The former is likely to be the source of the outer gas giants,and the latter is the source for the inner volatile-free rocky planets.Our study spans disks with a various range of accretion rates,and we find that tandem planet formation can occur for M = 10~(7.3)- 10~(-6.9)M_⊙yr~(-1).The rocky planets form between 0.4-2 AU,while the icy planets form between 6-30 All;no planets form in 2—6 AU region for any accretion rate.This is consistent with the gap in the solid component distribution in the solar system,which has only a relatively small Mars and a very small amount of material in the main asteroid belt from 2-6 AU.The tandem regime is consistent with the idea that the Earth was initially formed as a completely volatile-free planet.Water and other volatile elements came later through the accretion of icy material by occasional inward scattering from the outer regions.Reactions between reductive minerals,such as schreibersite(Fe-jP),and water are essential to supply energy and nutrients for primitive life on Earth.  相似文献