Detection of high-energy solar neutrons and protons by ground level detectors on April 15, 2001     

Y. Muraki  Y. Matsubara  S. Masuda  S. Sakakibara  T. Sako  K. Watanabe  R. Bütikofer  E.O. Flückiger  A. Chilingarian  G. Hovsepyan  F. Kakimoto  T. Terasawa  Y. Tsunesada  H. Tokuno  A. Velarde  P. Evenson  J. Poirier  T. Sakai 《Astroparticle Physics》2008,29(4):229-242

In association with the large solar flare of April 15, 2001, the Chacaltaya neutron monitor observed a 3.6σ enhancement of the counting rate between 13:51 and 14:15 UT. Since the enhancement was observed beginning 11 min before the GLE, solar neutrons must be involved in this enhancement. The integral energy spectrum of solar neutrons can be expressed by a simple power law in energy with the index γ=-3.0±1.0. On the other hand, an integral energy spectrum of solar protons has been obtained in the energy range between 650 MeV and 12 GeV. The spectrum can also be expressed by a power law with the power index γ=-2.75±0.15. The flux of solar protons observed at Chacaltaya (at 12 GeV) was already one order less than the flux of the galactic cosmic rays. It may be the first simultaneous observation of the energy spectra of both high-energy protons and neutrons. Comparing the Yohkoh soft X-ray telescope images with the observed particle time profiles, an interesting picture of the particle acceleration mechanism has been deduced.  相似文献   

山东半岛风电爬坡事件的识别与天气分析研究     

郭燕玲  赵晶  周林  张文煜  郭振海 《气候与环境研究》2017,22(1):97-107

根据山东省24个风电场2013年全年每15 min的风电输出功率实测数据以及相应的WRF(Weather Research and Forecasting)气象预测数据和FNL(Final Operational Global Analysis)再分析资料,分析了区域大规模风电爬坡现象与大尺度天气系统演变的联系。结果显示,大尺度天气系统,特别是阻塞高压系统,是诱发山东地区大规模风电爬坡的重要因素;爬坡事件的预测应当考虑天气演变的因素。进一步结合旋转门(The Swinging Door,TSD)算法重新讨论了爬坡事件的定义与识别,并在此基础上分析了爬坡事件的特征及其可预报性;并指出风电功率上报、考核制度应当重点考虑爬坡时间段的预测水平,以提高电网运行的稳定性。  相似文献   

北阿尔金地区古元古代岩体LA-ICP-MS锆石U-Pb年龄及其地质意义     

王斌  王永  陈柏林  陈正乐  吴玉  孟令通  何江涛  王玉刚  韩梅梅  祁万修  刘兵  赵雷 《地质通报》2017,36(6):964-976

北阿尔金是塔里木克拉通变质基底的主要出露区之一。对该区具有侵入接触关系的正长花岗岩和花岗片麻岩进行了LA-ICP-MS锆石U-Pb定年研究。正长花岗岩中的锆石多呈椭圆状,具有振荡环带结构,部分颗粒中可见老锆石残核,Th/U值较高,亏损轻稀土元素,富集重稀土元素,具有负Eu异常和正Ce异常的特点,表明该组锆石为岩浆成因。定年结果获得1903±13Ma和2506±55Ma两组年龄加权平均值,前者代表岩体的结晶年龄,后者为捕获锆石年龄,结合区域年代学资料,认为正长花岗岩岩浆侵入过程中可能捕获了太古宇米兰群的古老基底锆石。花岗片麻岩中16个测点的锆石~(207)Pb/~(206)Pb年龄集中于1802±28Ma,代表了岩体侵位时代,其余5个测点的锆石~(207)Pb/~(206)Pb年龄为1911~1951Ma,说明岩浆侵位过程中捕获了部分正长花岗岩的物质。区域地质与同位素年代学研究表明,北阿尔金地区广泛存在2.0~1.8Ga的构造-热事件。获得的花岗质岩石的1.9~1.8Ga的年龄结果,直接证实了北阿尔金存在约1.9Ga的岩浆作用,可能为古元古代Columbia超大陆汇聚事件在该地区的响应,为探讨塔里木板块前寒武纪构造-热事件演化历史提供了新资料。古元古代末期约1.8Ga的花岗片麻岩,代表了后造山伸展阶段的岩浆活动。  相似文献   

基于随机事件集的风暴潮重现期计算的合理性研究          下载免费PDF全文

李旋  龚茂珣  亢兴  陈昞睿 《海洋通报》2017,36(4):424-430

为了研究随机事件集实际应用于计算南通如东岸段风暴增水的合理性问题,基于ADCIRC模型模拟影响南通如东岸段基于随机事件集的风暴增水,然后利用P-Ⅲ型曲线对年增水极值进行拟合,得到各典型重现期下的增水值,并与由28年历史资料拟合得到的各重现期下增水值进行对比。结果表明,在历史资料长度所及的28年以及以下重现期,基于随机事件集模拟得到的重现期增水值与基于历史实测资料的比较符合,说明随机事件集的结果在低重现期情况下结果良好。对于高重现期增水值,基于随机事件集的拟合结果显著大于基于历史资料的拟合结果。由于历史资料时间太短,不足以发生非常极端的风暴潮事件,故对高重现期的拟合结果难以保证可信度,所以不能排除随机事件集拟合结果的合理性。随机事件集在南通如东岸段对低重现期增水估计准确,同时也能较充分地估计高重现期增水,在目前缺乏百年千年时间尺度的实测资料的情况下,不失为一种良好的风暴增水重现期计算工具。在全球变暖情况下,超强台风出现几率大大增加,典型重现期增水值也会相应提高,为了预防风暴灾害的侵袭,需要加深加固海堤、江堤等海岸工程。  相似文献   

汉南地区晋宁晚期铜-金成矿事件的确认及意义   总被引：1，自引：0，他引：1  

崔建军  曲玮  高福平  郑光高  赵文平  陈龙耀  李淼  刘林  于新兵 《矿床地质》2017,36(3):659-674

汉南地区位于扬子克拉通北缘西段。目前,在川、陕两省已在该区发现了数十个矿床(点)。其中,广泛分布的铜-金矿床(点)具有热液型矿化特征,成矿条件有利,具有寻找大-中型矿床的远景。为了查明这些铜-金矿产资源的形成时代,文章运用LA-ICP-MS锆石U-Pb法和单矿物~(40)Ar/~(39)Ar法对汉南地区有代表性的矿床(点)进行了成矿年代学研究。其结果显示,潘坝成矿期热液脉的锆石U-Pb年龄为(744±10)Ma,黑云母和钾长石~(40)Ar/~(39)Ar视年龄介于740 Ma~700 Ma之间。元山寺的成矿期白云母~(40)Ar/~(39)Ar坪年龄为(744±4)Ma,等时线年龄为(748±7)Ma。由于本次测试选择了成矿期矿物,其结果可以代表成矿时代。因此,汉南很可能存在晋宁晚期的铜-金成矿事件。根据区域地质演化历史,笔者认为汉南铜-金矿化(744 Ma)是造山晚期加厚岩石圈下部(山根)拆沉的结果。  相似文献   

Combined zircon and cassiterite U–Pb dating of the Piaotang granite-related tungsten–tin deposit,southern Jiangxi tungsten district,China     

《Ore Geology Reviews》2017

The large low-grade Piaotang W–Sn deposit in the southern Jiangxi tungsten district of the eastern Nanling Range, South China, is related to a hidden granite pluton of Jurassic age. The magmatic-hydrothermal system displays a zonation from an inner greisen zone to quartz veins and to peripheral veinlets/stringers (Five-floor zonation model). Most mineralization is in quartz veins with wolframite > cassiterite. The hidden granite pluton in underground exposures comprises three intrusive units, i.e. biotite granite, two-mica granite and muscovite granite. The latter unit is spatially associated with the W–Sn deposit.Combined LA-MC-ICP-MS U–Pb dating of igneous zircon and LA-ICP-MS U–Pb dating of hydrothermal cassiterite are used to constrain the timing of granitic magmatism and hydrothermal mineralization. Zircon from the three granite units has a weighted average ²⁰⁶Pb/²³⁸U age of 159.8 ± 0.3 Ma (2 σ, MSWD = 0.3). The cathodoluminescence (CL) textures indicate that some of the cassiterite crystals from the wolframite-cassiterite quartz vein system have growth zonations, i.e. zone I in the core and zone II in the rim. Dating on cassiterite (zone II) yields a weighted average ²⁰⁶Pb/²³⁸U age of 159.5 ± 1.5 Ma (2 σ, MSWD = 0.4), i.e. the magmatic and hydrothermal systems are synchronous. This confirms the classical model of granite-related tin–tungsten mineralization, and is against the view of a broader time gap of >6 Myr between granite magmatism and W–Sn mineralization which has been previously proposed for the southern Jiangxi tungsten district. The elevated trace element concentrations of Zr, U, Nb, Ta, W and Ti suggest that cassiterite (zone II) formed in a high-temperature quartz vein system related to the Piaotang granite pluton.  相似文献   

中国西北极端降水事件年内非均匀性特征分析   总被引：10，自引：2，他引：8  

杨金虎  江志红  王鹏祥  张小明 《中国沙漠》2008,28(1):178-184

 基于中国西北五省（区）1960—2004年112个台站逐日降水资料,根据百分位值方法定义了不同台站的极端降水阈值,引入了表征时间分配特征的新参数——极端降水事件集中度和集中期,对中国西北极端降水事件的年内非均匀性特征进行了分析,结果表明：西北年极端降水事件集中度及集中期的平均和异常空间分布都存在很大的区域差异,并且其异常空间分布均可分为6个关键区;而从时间演变来看,各个关键区年极端降水事件的集中度与集中期均表现出了显著的年代际振荡特征,但各分区年代际变化特征并不一致;另外西北东、西部年极端降水事件集中度与集中期表现出反向的变化趋势。  相似文献   

Suppression of internal multiples based on virtual events     

LIU Yi  LIU Yang  LU Qi 《世界地质(英文版)》2013,16(2):113-120

In practical seismic exploration, internal multiples generated when the wave impedance of medium is strong, and seismic records are recorded. The method of virtual event repress internal multiples is to move scattered points from underground to the surface, similar to the method of the surface-related multiple elimination (SRME). The method of SRME belongs to the prediction-subtraction approaches to eliminate internal multiples, prediction method is based on building a brand new way of seismic wave propagation (virtual reflection and virtual event), so that it has forward and backward wave propagation, and through convolution with significant wave to predict the internal multiples. Due to required data needing field information of full-wave, the authors use Seislet transform interpolating the missing data to ensure the premise of internal multiples prediction. The test data show that the above method has achieved good results.  相似文献   

中国热浪事件的大气扰动结构及其稳定性分析   总被引：4，自引：3，他引：1       下载免费PDF全文

钱维宏  丁婷 《地球物理学报》2012,55(5):1487-1500

利用对流层至平流层大气变量的物理分解,本文发现400 hPa上的天气尺度温度扰动正值和250 hPa上的天气尺度高度扰动正值能够指示地面上的高温和热浪事件.理论和观测分析发现,当扰动静止波中心出现在40°N-45°N时,准静止波波长较长,影响范围大,持续时间久,容易在中国形成区域持续性热浪事件.在江南-华南、长江沿江及河套-华北的区域,干热浪事件静止波的稳定时间在6.5天以上.对流层大气天气尺度扰动波动在垂直方向具有倾斜特征,250 hPa高度上,静止波稳定位置比地面热浪区域中心普遍偏北6~12个纬距.在低纬度(副热带高压带南侧),大气中向西北方向移动的天气尺度扰动,只有到达副高脊线以北的西风带后,才能形成静止波.  相似文献   

A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport     

Peng Gao  James Puckett 《地球表面变化过程与地形》2012,37(2):169-179

In this study, we proposed a new approach for linking event sediment sources to downstream sediment transport in a watershed in central New York. This approach is based on a new concept of spatial scale, sub‐watershed area (SWA), defined as a sub‐watershed within which all eroded soils are transported out without deposition during a hydrological event. Using (rainfall) event data collected between July and November, 2007 from several SWAs of the studied watershed, we developed an empirical equation that has one independent variable, mean SWA slope. This equation was then used to determine event‐averaged unit soil erosion rate, Q_S/A, (in kg/km²/hr) for all SWAs in the studied watershed and calculate event‐averaged gross erosion E_ea (in kg/hr). The event gross erosion E_t (in kilograms) was subsequently computed as the product of E_ea and the mean event duration, T (in hours) determined using event hydrographs at the outlet of the studied watershed. Next, we developed two linear sediment rating curves (SRCs) for small and big events based on the event data obtained at the watershed outlet. These SRCs, together with T, allowed us to determine event sediment yield SY_e (in kilograms) for all events during the study period. By comparing E_t with SY_e, developing empirical equations (i) between E_t and SY_e and (ii) for event sediment delivery ratio, respectively, we revealed the event dynamic processes connecting sediment sources and downstream sediment transport. During small events, sediment transport in streams was at capacity and dominated by the deposition process, whereas during big events, it was below capacity and controlled by the erosion process. The key of applying this approach to other watersheds is establishing their empirical equations for Q_S/A and appropriately determining their numbers of SWAs. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献