A Statistical Study of Rapid Sunspot Structure Change Associated with Flares

We reported recently some rapid changes of sunspot structure in white-light(WL) associated with major flares.We extend the study to smaller events and present here results of a statistical study of this phenomenon.In total,we investigate 403 events from 1998 May 9 to 2004 July 17,including 40 X-class,174 M-class,and 189 C-class flares.By monitoring the structure of the flaring active regions using the WL observations from the Transition Region and Coronal Explorer(TRACE),we find that segments in the outer sunspot structure decayed rapidly right after many flares;and that,on the other hand,the central part of sunspots near the flare-associated magnetic neutral line became darkened.These rapid and permanent changes are evidenced in the time profiles of WL mean intensity and are not likely resulted from the flare emissions.Our study further shows that the outer sunspot structure decay as well as the central structure darkening are more likely to be detected in larger solar flares.For X-class flares,over 40% events show distinct sunspot structure change.For M-and C-class flares,this percentage drops to 17% and 10%,respectively.The results of this statistical study support our previously proposed reconnection picture,i.e.,the flare-related magnetic fields evolve from a highly inclined to a more vertical configuration.     

Sensitive response of desert vegetation to moisture change based on a near-annual resolution pollen record from Gahai Lake in the Qaidam Basin, northwest China

We present a 50-year pollen record at near-annual resolution from Gahai Lake in the Qaidam Basin on the northeastern Tibetan Plateau. Chronology of a 22-cm short core was established by ²¹⁰Pb and ¹³⁷Cs analysis. The pollen results at 0.5 cm intervals show large changes in Artemisia/Chenopodiaceae (A/C) ratios from < 0.2 to 0.95 in the last 50 years. High (low) A/C ratios represent increase (decrease) in steppe pollen production, which correspond to high (low) relative humidity observed at nearby Delingha weather station. On the basis of good correspondence with instrumental records and carbonate content from Gahai Lake, we conclude that A/C ratio is sensitive to moisture change and can be a very useful index in reconstructing paleoclimate of arid regions. Comparison with pollen and snow accumulation data from Dunde ice core suggests that effective moisture at low and high elevations shows the opposite relationship when mountain precipitation was extremely high, possibly due to topography-induced uplifting and subsiding air dynamics.     

Magnetic Twist and Writhe of δ Active Regions

We have selected 104 active regions with a δ magnetic configuration from 1996 to 2002 to study how important a role the kink instability plays in such active regions. In this study, we employ the systematic tilt angle of each active region as a proxy for the writhe of a flux tube and the force-free parameter, α_best, as a proxy for the magnetic field twist in the flux tube. It is found that 65–67% of the active regions have the same sign of twist and writhe. About 34% (32%) of the active regions violate (follow) the Hale-Nicholson and Joy's Laws (HNJL) but follow (violate) the hemispheric helicity rule (HHR). Sixty-one (61) of the 104 active regions studied each produced more than five large flares. Active regions violating HNJL, but following HHR, have a much stronger tendency to produce X-class flares and/or strong proton events. Comparing with previous studies for active regions with well-defined (simpler) bipolar magnetic configuration, it is found that the numbers following both HNJL and HHR are significantly lower in the δ-configuration case, while numbers violating one of the laws and the rule significantly increase with the increase of the magnetic complexity of the active regions. These results support the prediction for the presence of a kink instability, that the twist and writhe of the magnetic fields exhibit the same sign for δ active regions (Linton et al., Astrophys. J. 507, 40, 1998, Astrophys. J. 522, 1205, 1999; Fan et al., Astrophys. J. 521, 460, 1999). Finally, we analyze possible origins of the twist and writhe of the magnetic fields for the active regions studied.     

Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 m equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 m EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K₂SO₄,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.     

横断山脉地区大气环流演变特征分析

应用Lamb-Jenkinson大气环流分型方法对横断山脉地区的8个经度×10个纬度范围内1948-2012年逐日平均的海平面气压场进行环流分型,由日平均海平面气压场算出6个环流指数（u、v、V、ξu、ξv、ξ）,并由此划分出27种不同的环流型。分型结果表明：横断山脉地区主要环流分型为E型、NE型、SE型、N型和C型,其频率分别为：21.4%、14.6%、13.7%、9.8%和9.5%;E和NE型环流频率逐渐增加,C型环流型频率逐渐减少。春季横断山脉地区主导环流比较繁琐;NE、N型为夏季的主要环流型,但E型环流在夏季的频率也相当大;秋季和冬季横断山脉地区的主导环流型都为E型和SE型。夏季主导环流型持续时间较长,冬季也是主导环流持续的时间较长,个别年份主导环流型持续时间超过了一个月,这主要与横断山脉地区复杂的地形有联系。     

湖南锡田矿田花岗岩时空分布与钨锡成矿关系:来自锆石U-Pb年代学与岩石地球化学的约束

锡田钨锡多金属矿田位于南岭成矿带中段,发育多期次岩浆活动与钨锡成矿. 为了厘清花岗岩与钨锡成矿的时空关系,采用野外调查、显微鉴定、锆石U-Pb同位素定年与岩石地球化学的方法对矿田内多期次花岗岩岩体（脉）的空间分布、岩石类型、成岩时代、地球化学组成等进行了研究. 结果表明,锡田矿田发生了三期岩浆事件,分别为加里东期（435~441 Ma）、印支期（220~230 Ma）、燕山期（141~160 Ma）;三期花岗岩普遍富集大离子亲石元素Rb、K、U、Th等,亏损Ti、P、Sr、Ba等微量元素,具明显的负Eu异常,其中加里东期花岗岩与印支期花岗岩为S型花岗岩,而燕山期花岗岩为A型花岗岩;不同时期花岗岩中的成矿元素从加里东期→印支期→燕山期逐渐升高,特别是W、Sn元素在燕山期白云母与二云母花岗岩中最为富集,这与华南地区燕山期钨锡大爆发的时间是一致的;印支期岩体接触带发育少量矽卡岩型Fe-Cu-W多金属矿床,燕山期岩体接触带也发育矽卡岩型W-Sn多金属矿床,并在附近陡倾的张裂隙中发育多个中大型石英脉型W-Sn矿床,而加里东期岩体附近尚未发现钨锡矿化. 因此,锡田矿田的多期次花岗岩与钨锡多金属成矿是时空耦合的,且成矿以燕山期矽卡岩型与石英脉型钨锡矿为主.      

长江流域沿江镉异常源追踪与定量评估的方法技术研究:以长江流域安徽段为例

长江全流域性的Cd异常是被中国正在进行的多目标地球化学调查发现的重大生态环境问题。以长江流域安徽段为研究对象,对沿江镉异常源追踪与定量评估的方法技术进行了系统研究。通过对安徽段长江干流及其主要支流悬浮物中元素含量的测量查明:悬浮物是流域内重金属元素大跨度迁移的主要载体;Cd在悬浮物中的富集程度远远大于其他重金属元素,这或许正是Cd可以形成沿江流域性异常的主要原因;长江干流悬浮物中重金属元素含量的变化明显受到沿江支流的影响。安徽段长江干流及其主要支流重金属元素输出通量定量计算结果表明:秋蒲河是安徽段重金属元素输出通量最大的支流,每年在安徽段长江两岸土壤中沉积下约4.45t的Cd。利用悬浮物加密测量、1∶5万土壤测量和岩石测量对顺安河流域Cd异常源追踪结果显示:内生金属矿床特别是铅锌矿是悬浮物中Cd的最大的供应源。采用河漫滩沉积物分层采样技术和同位素测年技术,初步恢复了研究区Cd等重金属元素沉积和污染的地球化学历史,对研究区Cd等重金属元素异常的未来演变趋势进行了预警预测。     

塔里木盆地西南缘的岩石组合及其构造演化

塔里木盆地西南缘可划分为喀喇昆仑、西昆仑、塔里木等三个地层区和康西瓦、库地等两个缝合带。自震旦纪以来,该区经历了震旦纪—泥盆纪和石炭纪—第四纪两大构造旋回。对应每一旋回,喀喇昆仑地层区和塔里木地层区发育有被动大陆边缘盆地和碰撞造山两种类型的岩石组合。西昆仑地层区发育了被动大陆边缘盆地、俯冲消减带和碰撞造山等三种类型的岩石组合。康西瓦缝合带是康西瓦洋经历了震旦纪—中泥盆世和早石炭世—晚侏罗世两次开合后的遗迹,它既是喀喇昆仑和西昆仑两个地层区的分界线,又是羌塘和塔里木两个板块的分界线;库地缝合带则是库地洋经历早石炭世—早二叠世一次开合的遗迹,分割了西昆仑和塔里木这两个地层区。     

Observations of Giant Pulses of the Crab Pulsar

The Crab Pulsar was observed at 1540 MHz with the 25m radio telescope at Urumqi with a filterbank de-dispersion backend. A total of 2436 giant pulses with pulse energies larger than 4300 Jy μs were detected in two observing sets. All of these giant pulses are located in the main pulse (MP) and inter pulse (IP) windows of the average profile of the Crab Pulsar. The ratio of the numbers of giant pulses detected in the IP and MP windows is about 0.05. Our results show that, at 1540 MHz, the emission in the IP is contributed by giant and normal pulses, while that in the MP is almost dominated by giant pulses. The distribution of energy of the 2436 giant pulses at 1540 MHz can be described by a power-law with index α=3.13±0.09. The intrinsic threshold of giant pulse energy in the MP window is about 1400 Jy μs at 1540 MHz.     

扬子克拉通北缘中元古界神农架群沉积特征*

神农架群(约1400—1000 Ma)发育于扬子克拉通北缘鄂西北地区,自下而上发育有下亚群(大岩坪组、马槽园组、乱石沟组、大窝坑组和矿石山组)、中亚群(台子组、野马河组、温水河组和石槽河组)及上亚群(送子园组和瓦岗溪组)。每亚群均由相对较深水相碎屑岩和浅水碳酸盐岩组成。一系列岩石组合特征、宏微观沉积组构和沉积构造等表明,神农架群发育环潮坪相藻碳酸盐岩、浅海相碎屑岩、台缘浅滩颗粒碳酸盐岩和台缘斜坡砾屑碳酸盐岩等4类沉积组合,形成于远端变陡型缓坡型碳酸盐岩台地背景。环潮坪沉积分布最广,遍布于所有碳酸盐岩地层,不同类型叠层石发育,构成向上变浅沉积序列;进积作用强烈,干裂构造、蒸发岩等常见;沉积相带由浅潮下、潮坪及潮上带组成。浅海碎屑岩沉积组合主要见于台子组及大岩坪组,由砂岩、粉砂岩与泥岩组成,石英砂岩分选和磨圆较好,自生海绿石常见,平行层理、水平—波状层理发育,泥岩中自生黄铁矿发育,总体经历了滨岸浅滩—浅海陆棚—碎屑潮坪—局限台地等的高频变化。台缘浅滩颗粒碳酸盐岩以鲕粒白云岩、砾屑白云岩(及内碎屑白云岩)和斜歪锥、柱状叠层石为特征,主要见于乱石沟组、野马河组;大窝坑组及石槽河组以鲕粒和砂—砾屑白云岩及藻碎屑(团块或凝块石)为特征;大中型板状交错层理、递变—平行层理和冲刷—侵蚀构造普遍,表明浅潮下带强水动力条件环境。台缘斜坡砾屑碳酸盐岩发育在大岩坪组中上部及马槽园组,由滑塌堆积的透镜状、巨厚层状巨—粗—细砾岩和砂岩组成,砾岩成分以白云岩等为主,可见大型交错层理、波痕和侵蚀—冲刷等沉积构造。对神农架群沉积序列、沉积特征及沉积演化过程的研究,为扬子克拉通中元古代晚期的盆地演化与重建、沉积充填过程及地层—沉积对比研究提供了基础资料及依据。