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21.
Type-I bursts (i.e. noise storms) are the earliest-known type of solar radio emission at the meter wavelength. They are believed to be excited by non-thermal energetic electrons accelerated in the corona. The underlying dynamic process and exact emission mechanism still remain unresolved. Here, with a combined analysis of extreme ultraviolet (EUV), radio and photospheric magnetic field data of unprecedented quality recorded during a type-I storm on 30 July 2011, we identify a good correlation between the radio bursts and the co-spatial EUV and magnetic activities. The EUV activities manifest themselves as three major brightening stripes above a region adjacent to a compact sunspot, while the magnetic field there presents multiple moving magnetic features (MMFs) with persistent coalescence or cancelation and a morphologically similar three-part distribution. We find that the type-I intensities are correlated with those of the EUV emissions at various wavelengths with a correlation coefficient of 0.7?–?0.8. In addition, in the region between the brightening EUV stripes and the radio sources there appear consistent dynamic motions with a series of bi-directional flows, suggesting ongoing small-scale reconnection there. Mainly based on the induced connection between the magnetic motion at the photosphere and the EUV and radio activities in the corona, we suggest that the observed type-I noise storms and the EUV brightening activities are the consequence of small-scale magnetic reconnection driven by MMFs. This is in support of the original proposal made by Bentley et al. (Solar Phys. 193, 227, 2000). 相似文献
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闽东南地区降雨侵蚀力的初步研究 总被引:7,自引:0,他引:7
本文利用实测降雨与径流小区资料对闽东南地区不同降雨类型的雨强等特点及其对土壤侵蚀的影响进行了分析;提出了60分钟瞬时最大雨强为侵蚀性降雨指标,其指标在该地区为I60≥9mm;建立了研究区年侵蚀力R值的简便算式,并根据谝绘制了研究区R值分布图。 相似文献
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A STUDY ON THE RELATIONSHIP BETWEEN THE ROTATION OF BINARY TYPHOONS AND STEERING CURRENT 总被引:1,自引:0,他引:1
Many studies show that, within a certain distance (ca. 700-800 n mi), two typhoons forming a binary typhoon (BT) system would rotate as a whole and attract each other, which is known as “Fuji-whara Effect” (FE). This paper indicates that only 30.3% of BTs has experienced remarkable cyclonic rotation with a 12-hr angle ≥+10° when two components are less than 20° lat apart, and that the probability is much higher with the eastern, component in the NE than in the SE quadrant for the western one, implying the steering effect of the environmental flow field (EFF) on them.47 observations from 13 BTs are separately used for calculating the angular velocity due to FE and EFF and the results are compared. The conclusion can be stated as follows: FE is dominant with the centers of two elements below 7° lat apart; the EFF steering current plays a major role when they are in the range of 7-15° and for a distance above 15° the principle of FE holds no longer. 相似文献
26.
在详细介绍模糊信息分配原理的基础上,结合模糊近似推论及信息集中原理,以地电手段为例,将模糊信息处理法应用于地震的三要素预报,取得了良好的结果。实践证明这种新方法在地震预报的各种手段中均有推广价值,方法本身具有客观、自完善功能,并可用于其它领域的模糊关系处理上。 相似文献
27.
红粘土地区水泥土强度的试验研究 总被引:7,自引:0,他引:7
红粘土是亚热带气候条件下形成的一种特殊土质。含有红粘土的地基多具有上硬下软的特点,下部红粘土为天然地基软弱下卧层。采用深层搅拌法处理,可充分发挥上部硬塑红粘土的作用,形成复合地基。通过试验得到了水泥红粘土的基本力学参数。在对试验结果进行回归分析后,给出了水泥土强度的影响因素及其与强度的关系,以及不同水泥掺量、龄期水泥土之间的强度推算公式。 相似文献
28.
分析1950年以来中等强度以上的ElNiño和LaNina当年和次年夏季(7月)低纬度风场和500hPa高度距平场,发现有不同的特征。其中中-西太平洋近赤道地区850、200hPa上风场异常变化十分明显,这种异常变化与南北半球大气相互作用有密切关系。在500hPa高度距平场上,北半球中、高和低纬地区表现出不同的正、负距平分布型式。上述特点对气候短期预测有一定参考意义。 相似文献
29.
External seismic stability of vertical geosynthetic-reinforced soil walls using pseudo-static method
Analysis of external stability of vertical geosynthetic-reinforced soil (GRS) walls is very important in the seismic prone zone. The scope of this paper is to obtain required minimum reinforcement length, L min, for external seismic stability of vertical GRS walls by pseudo-static limit equilibrium method. Then, L min can be calculated to resist sliding, eccentricity, and bearing capacity failure modes. The parameters considered include both horizontal and vertical seismic coefficients (k h and k v ), surcharge load (q), wall height (H) and the properties of retained backfill, GRS, and foundation soil. Results show that L min against sliding failure mode, L min,S , increases more quickly than that against the other two failure modes with the increase in k h , q, or unit weight of retained backfill, γ b , while L min,S decreases more quickly than that against the other two failure modes with increase in friction angle of retained backfill, ? b , or unit weight of GRS, γ r . For the different failure modes, the effect of k v on L min is not identical with the change of k h , and in addition, L min/H will tend to remain unchanged with the increase in H. In general, L min against bearing capacity failure mode, L min,BC, is larger than L min against the other two failure modes. However, L min,BC will be less than L min against eccentricity failure mode, L min,E , for k h exceeding 0.35, or friction angle of foundation soil, ? f , exceeding 37°, and L min,BC will also be less than L min,S for friction angle of GRS, ? r , being no more than 26°. 相似文献
30.
采用风廓线雷达5波束探测模式的数据对测风精度进行评估分析,用垂直波束和其中两个相邻倾斜波束的探测数据构成一对计算因子,通过对同一距离高度上的4对计算因子进行误差分析,评估风廓线雷达的测风精度,得到水平风在垂直指向连续高度上的精度。对北京延庆CFL-08风廓线雷达2010年3,6,9,12月4个典型代表月份逐日连续探测资料进行了处理分析,结果表明:该雷达满足风速误差不大于1.5 m·s-1、风向误差不大于10°探测精度要求的最大探测高度6月、9月为8 km,3月、12月为6 km,基本符合该雷达探测高度的设计要求。信噪比、大气风场的不均匀性是影响雷达测风精度的主要因素:信噪比影响了高空的测风精度,-15 dB可以作为判断雷达测风可信数据最大探测高度的阈值;晴空大气出现的风场不均匀性对风廓线雷达的测风精度影响不大,降水出现时环境风场不均匀性造成水平风向、风速的测量误差较大,不能满足测风精度要求,特别是对流性降水发生前的1~2 h,水平风向、风速的方差增长迅速,可以作为强降水出现的预警指标。 相似文献