Magneto-acoustic wave oscillations in solar spicules     

A. Ajabshirizadeh  E. Tavabi  S. Koutchmy 《Astrophysics and Space Science》2009,319(1):31-35

Some observations suggest that solar spicules show small amplitude and high frequency oscillations of magneto-acoustic waves, which arise from photospheric granular forcing. We apply the method of MHD seismology to determine the period of kink waves. For this purposes, the oscillations of a magnetic cylinder embedded in a field-free environment is investigated. Finally, diagnostic diagrams displaying the oscillatory period in terms of some equilibrium parameters are provided to allow a comparison between theoretical results and those coming from observations.   相似文献   

Fitting of expanding magnetic clouds: A statistical study     

A. Lynnyk  M. Vandas 《Planetary and Space Science》2009,57(12):1375-1380

Magnetic clouds (MCs) observed by Wind during the 1995-2003 years and listed in Lepping et al. [2006. A summary of WIND magnetic clouds for years 1995-2003: model-fitted parameters, associated errors and classifications. Ann. Geophys. 24(1), 215-245] are fitted using force-free cylindrical flux rope models. The cloud parameters yielded by a static model are compared with those obtained from a modified model that includes magnetic cloud expansion. The deviations of these fits from observations are quantified using 1 h averages of measured parameters by Wind. In the case of the static MC model, the deviations between fitted and observed magnetic fields increase with the magnetic strength and with the MC radius. The comparison of both the static and the dynamic models reveals that the modified model with expansion provides better fits in the range of low expansion speeds , whereas the results are not conclusive for larger expansion speeds. The dynamic model provides better fits than static one in 70% of investigated MCs. We conclude that the expansion of magnetic clouds plays an important role in the MC formation and propagation but a further progress requires determination of cloud parameters from a model with expansion self-consistently involved.  相似文献   

Contaminant fluxes from point and diffuse sources from abandoned mines in the River Tamar catchment, UK     

Krongkaew Mighanetara  Charlotte B. Braungardt  John S. Rieuwerts  Fethi Azizi   《Journal of Geochemical Exploration》2009,100(2-3):116-124

Acid mine waters have the potential to seriously impair the environmental quality of aquatic systems long after mining activities have ceased. This detailed study of dissolved and particulate metal fluxes from adits, drains and streams in the River Tamar catchment, southwest England, showed that seven specific sources, of the 25 adits and streams surveyed, accounted for more than 75% each of the 13 t a^− 1 Fe, 4.3 t a^− 1 Mn, 4.2 t a^− 1 Cu, 3.6 t a^− 1 Zn and 1.4 t a^− 1 As that we estimated to be discharged annually from the abandoned metalliferous mining area centred around Calstock and Gunnislake. Upstream of this study area, widespread multi-metallic mineralisation contributed to the flux of Fe, Mn, As, Co, Cu and Zn within the River Tamar. Simple mass balance calculations indicated that a large proportion (≥ 50% for most dissolved and particulate metals) of the metal flux in the River Tamar was unaccounted for by our survey, and therefore is likely to have an important diffuse component, which is subject to ongoing investigations. Potential impacts of mine contamination on the estuarine environment are discussed. The study provided information necessary to prioritise monitoring and remediation efforts in the context of sustainable catchment management.  相似文献   

大孔径闪烁仪的通量印痕分析与应用   总被引：1，自引：0，他引：1  

蔡旭晖  朱明佳  刘绍民  徐自为 《地球科学进展》2010,25(11):1166-1174

针对北京密云站的长期通量观测进行大孔径闪烁仪的平均印痕区域分析.首先从2008年全年8 152组湍流观测资料,以整体湍流特征量σu/u*以及其他数据合理性判据进行质量控制,获得6 806组有效数据;然后用一个解析解模型逐时次计算大孔径闪烁仪的二维印痕,并进行统计平均,获得各季平均印痕分布;将当地气象条件根据风向、风速和稳定度分为12类,分别统计各类条件的平均印痕分布.最后,以实测感热通量为例,计算当地实际湍流通量的气候平均印痕区域.结果表明,当地大孔径闪烁仪的平均通量印痕季节变化不大;各类气象条件中,稳定度和风向是影响印痕区域大小和方向的重要因素,风速影响相对较小;以实际湍流通量为权重的气候平均印痕可更准确反映观测结果的空间代表性,其分布与简单平均的印痕分布有所不同.  相似文献   

大孔径闪烁仪法测算低丘山地人工混交林显热通量的可行性分析     

张劲松  孟平  郑宁  黄辉  高峻 《地球科学进展》2010,25(11):1283-1290

利用位于河南省济源市的华北低丘山地30年生栓皮栋-侧柏-刺槐人工混交林2009年主要生长季节(5-9月)湍流通量及空气结构参数等观测数据,确定迭代法为该下垫面条件下大孔径闪烁仪(LAS)测算显热通量的计算法,测算白天大气非稳定层结状况下的显热通量(HLAS).并采用通量印痕模型,对LAS法通量源区内由2台涡度相关系统观测得到的显热通量进行订正,得到源区内总显热通量值(HfEC).分析LAS法与涡度相关法的显热通量测算或测定值的相关性,结果表明:HLAS与HfEC的线性相关系数可达0.93.说明在分析通量印痕和通量源区的基础上,采用LAS法测算低丘山地人工混交林显热通量具有较好的可行性.  相似文献   

Expulsion of magnetic flux lines from the growing superconducting core of a magnetised quark star     

Somenath Chakrabarty 《Astrophysics and Space Science》2008,314(1-3):105-112

The expulsion of magnetic flux lines from a growing superconducting core of a quark star has been investigated. The idea of impurity diffusion in molten alloys and an identical mechanism of baryon number transport from hot quark-gluon-plasma phase to hadronic phase during quark-hadron phase transition in the early universe, micro-second after big bang has been used. The possibility of Mullins-Sekerka normal-superconducting interface instability has also been studied.  相似文献   

安徽歙县伏川蛇蚊岩矿     

甘远生 《云南地质》2011,30(3):329-331

伏川超基性岩体已全部蚀变成蛇纹岩,原岩为贵橄榄岩及顽火辉石岩,可用于熔剂材料。  相似文献   

水下图像基于 GAN 去模糊的增强技术          下载免费PDF全文

王宏妫  史先鹏 《海洋科学进展》2022,40(2):342-350

利用海洋模式FVCOM(FiniteVolume,primitiveequationCommunityOceanModel)建立了一个高分辨率的舟山附近海域潮汐潮流模型,通过与历史实测资料进行对比验证了模型模拟结果的可靠性,表明模型可以较好地描述舟山附近海域潮汐潮流运动状况。基于模型的模拟结果,估算与分析了舟山西堠门水道的潮流能资源,结果表明,西堠门水道的潮流以往复流为主,年平均流速和年最大流速分别超过1.2m/s和2.6m/s,年平均能流密度和年最大能流密度分别超过1.2kW/m2 和6.5kW/m2;西堠门水道的平均流速和平均能流密度存在3处峰值区,其值大小由西北向东南递增;西堠门水道流速和能流密度的季节分布特征相似,1月(冬季)的流速和能流密度最大,4月(春季)和10月(秋季)次之,7月(夏季)最小。结合潮流能发电站选址原则,本文认为册子岛西北岬角处海域可选为西堠门水道潮流能发电站的最佳场址,其总平均功率和有效功率分别为30.0 MW 和4.5 MW,与当前已经运行的潮流能发电站相比较,该选址区域的发电能力较为可观,具有极大开发潜力。  相似文献   

Influence of the solar activity on the Indian Monsoon rainfall   总被引：1，自引：0，他引：1  

K. M. Hiremath  P. I. Mandi 《New Astronomy》2004,9(8):651-662

We use 130 years data for studying correlative effects due to solar cycle and activity phenomena on the occurrence of the Indian Monsoon rainfall. We compute the correlation coefficients and significance of correlation coefficients for the seasonal and the annual data. We find that: (i) for the whole years 1871–2000, the spring and southwest monsoon rainfall variabilities have significant positive correlations with the sunspot activity during the corresponding period, (ii) the FFT and the wavelet analyses of the southwest monsoon rainfall variability show the periods 2.7, 16 and 22 year, respectively (similar to the periods found in sunspot occurrence data) and, (iii) there is a long-term trend indicating a gradual decrease of occurrence of rainfall variability by nearly 2.3 ± 1.3 mm/year and increase of sunspot activity by nearly 3.9 ± 1.5 sunspots/year compared to the activity of previous solar cycle.

We speculate in this study a possible physical connection between the occurrence of the rainfall variability and the sunspot activity, and the flux of galactic cosmic rays. Owing to long-term positive and significant correlation of the spring and southwest monsoon rainfall variabilities with the sunspot activity, it is suggested that solar activity may be included as one of the crucial parameter in modeling and predicting the Indian monsoon rainfall.  相似文献   

Some Opinions on Rock-Weathering-Related Carbon Sinks from the IPCC Fifth Assessment Report   总被引：2，自引：0，他引：2  

Pu Junbing  Jiang Zhongcheng  Yuan Daoxian  Zhang Cheng 《地球科学进展》2015,30(10):1081-1090

Many recent researches show that rock-weathering-related carbon sink, especially carbonate-weathering-related carbon sink, actively takes part in the modern global carbon cycle, which might greatly contribute to balancing global carbon budget. Some new opinions on flux, time scale and effect of rock-weathering-related carbon sink were released in IPCC fifth Assessment Report (AR5). The flux of global rock-weathering-related carbon sink is about 0.4 Pg C/a in AR5 report, which accounts for about 1/2~1/3 of unbalanced global carbon budget. New time scale of global rock-weathering-related carbon sink was released. Time scale of silicate-weathering-related carbon sink is 10⁴~ 10⁶ year, while carbonate-weathering-related carbon sink (karst processes) is 10³~10⁴ year. A highlight is that rock-weathering-related carbon sink is listed as one of four carbon dioxide removal methods in AR5 report, whose time scale is 10²~ 10³ year. Although AR5 report released these new opinions, it is still thought that the rate of global rock-weathering-related carbon sink is currently too small to offset the rate at which fossil fuel CO₂ is being emitted. According to many researches in the field of rock weathering science in the past decades, this review discussed the shortage in carbon flux, time scale and effect of rock-weathering-related carbon sink in AR5 report. Many recent researches indicated that the carbon sink originated from carbonate rock weathering was a fast and sensitive geochemical process, which showed multiple time scales (diel, seasonal, annual or storm event). A new model based on H₂O carbonate-CO₂-aquatic phototroph interaction was established, which coupled geological, land surface water, and submerged phototroph carbon cycle process. The global carbon sink from carbonate rock weathering in new model is 0.477 Pg C/a,which accounts for about 39%~59% of unbalanced global carbon budget. Some key scientific issues on rate, stability, controlling mechanisms and scaling of rock-weathering-related carbon sink should be vitally concerned in the future, which could greatly contribute to balancing the global carbon budget.  相似文献