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对北京十三陵地磁台站2005年全年的地磁数据进行了统计分析,总结了该地区Pc6脉动的周期分布和发生率等特征.对Pc6脉动与TID的关系也做了一些尝试性探讨.我们选择北京大学多普勒雷达观测到TID事件同十三陵台站观测到Pc6脉动进行比较研究,在2004年12月23日至2006年3月11日这段时间内,共有42个事件满足要求.经过分析发现TID事件与Pc 6脉动在波动频率和波形上有比较好的相关性,讨论了Pc6脉动与TID可能的诱发源. 相似文献
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南极中山站和戴维斯站(不变磁纬74.5°)白天中午位于磁层极隙区,两站均安装了完全相同的感应式磁力计,选择1997年3月和1996年6、9、12月两站的数据,运用快速傅里叶变换和波形检查方法选择Pc3脉动事件,然后用信号互谱技术进行统计分析.结果如下:在中山站-戴维斯站,Pc3脉动主要出现于白天,尤其是中午/磁中午附近;Pc3脉动振幅及发生率均在6月份最小,在其他月份大些;Pc3脉动传播方向,白天主要向西.这些可能反映了电离层电导率和日侧电离层电流系统对Pc3脉动的影响. 相似文献
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采用IMAGE链22个台站的地磁脉动10 s数据，分析了2000年6月15～16日磁暴期间Pc5地磁脉动的频率、振幅、位相和极化特征：（1）磁暴初相和主相期间Pc5脉动的主频率随纬度的升高而降低，但是恢复相期间主频率随纬度的升高而升高，主相期间Pc5的主频率比初相和恢复相期间的低；（2）Pc5脉动初相期间的振幅有一个主峰在64°N附近，主相期间在66°N附近，恢复相期间在71°N附近；位相在主峰两侧随着纬度变化了大约180°， 从初相到恢复相主峰位置向高纬地区大约移动了7°；（3）Pc5地磁脉动的偏振极化椭圆初相期间在PEL站（6346°N）接近线偏振，主相期间在MAS站（6607°N）接近线偏振，恢复相期间在BJN站（7133°N）接近线偏振，并分别在这几个台站两侧的偏振椭圆的旋转方向反向. 相似文献
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南极中山站和戴维斯站均位于极隙区纬度附近,均安装了完全相同的感应式磁力计.选择两站的数据,1997年3月和1996年6、9、12月,运用信号互谱技术进行统计分析,结果得到:在中山站-戴维斯站,Pc5脉动出现时间范围较广,但以地方时中午/磁中午及磁午夜附近出现频次多,其振幅、传播及发生率季节变化不大.振幅白天变化小,中午有小峰,夜间有时有大值.传播方向白天以磁中午为界,晨侧向西传播,直至磁凌晨;昏侧向东传播,约在5:00MLT处转向.夜间约以20:00 MLT为界,之前向西传播,之后向东传播,磁黄昏附近,Pc5脉动传播方向变化较多,显得不规则.这些特征,反映了Pc5脉动在不同地方时段有不同的起源. 相似文献
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2007年3月3日位于磁层昏侧THEMIS的5颗卫星、同步轨道晨侧和午前的GOES 3颗卫星和地面地磁台站同时观测到了持续近4 h的Pc5 ULF波.我们用交叉小波相关分析计算脉动的传播速度,用MVA分析求解脉动的传播方向,然后结合两者的计算结果获得了Pc5相速度矢量信息.THEMIS卫星观测到Pc5具有压缩特性,且向阳传播,速度约在6~20 km/s左右,相比于磁层中阿尔芬速度(1000 km/s)较低.这些Pc5 ULF波动可能产生于磁尾或磁层内部不稳定性.GOES 3颗卫星观测到不同情况的Pc5 ULF波,极向模占主要成分,且具有波包结构,具有阿尔芬驻波特性,可能产生于K-H(Kelvin-Helmholtz)不稳定性.地面台站观测到ULF波扰动幅度随纬度升高而增强,Pc5脉动在地理纬度60°附近达到最大值, Dumont durville台站观测到的脉动与THEMIS观测到波形有很好的相似性. 相似文献
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作者在前一篇文章里分析每月五天国际磁扰日在太阳自轉周里的頻率分布,得到下述两个結論: 1.国际地磁干扰日在太阳自轉周里确实存在着一个不变的頻率分布,地磁場发生干扰的可能性,在頻率高的日序里約为在頻率低的日序里的二倍。 2.太阳的活动性,在太阳經圈上的分布是不均勻的,有些部分活动性強,有些部分活动性弱。 相似文献
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基于江苏省新沂台和山东省马陵山台同(近)场地观测的地磁场、地电场和分量应变观测数据,详细分析了两台站地电场日变化的波形、变幅、相位和优势周期成分以及日变幅的季节效应和台址电性条件对其的影响,并在此基础上分析了地电场日变化的机理.结果显示:① 两台站地电场日变化主要为两次起伏变化,主相起伏集中在当地午前午后时段,且起伏波形与磁场日变化的起伏波形大致相同,存在相位差,但主相起伏时段与磁场对时间的偏导曲线上的日变化起伏时段大致对应;地电场变化与磁场正交分量的变化显著相关,且与同方向的分量应变显著相关;地电场日变化波形与分量应变日变波形有很大差异;② 两台站地电场、地磁场日变化的优势周期为12 h,8 h,24 h,最显著周期为12 h,其中12 h和24 h周期成分是应变分量的优势周期;③ 两台站同方向地电场日变化的波形高度相似,但同台正交分量之间的日变幅有方向性差异;朔望月时段的日变幅大于上下弦月时段,日变幅有夏季大于冬季的季节效应;台址电导率越低,日变幅越大.地电场日变化既表现为广域性特征,又表现为局部性特征.地电场日变化机理分析认为,地电场日变化是由月日潮汐力和太阳风引起的电离层活动所导致,同时还受到季节、台址电性条件等多因素的影响. 相似文献
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目前,在远海开阔性海域磁测中,尚难以有效设立日变站,致使日变改正仍存在着困难.本文利用地磁台站实测资料对地磁日变的纬度分布特征进行研究,发现日变值随纬度变化具有由Sq电流中心向南北两侧递增的规律,且二者之间的关系可用二次函数近似描述。以此规律为基础我们建立了纬度改正方法,该方法以经度链为基站,利用基站数据得到日变值与磁纬度的拟合函数以进行纬度改正,再调整时差作为经度校正即得到计算站的日变值.实测数据计算结果表明,相较于加权平均法,此方法在远距离(经度差达40°)仍能保持较高的校正精度(4 nT),因而能更好地适用于远海磁测. 相似文献
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The time variability of diurnal tides was investigated by analyzing gravity observations from global superconducting gravimeter (SG) stations with running time intervals. Through least-square and Bayesian approaches, FCN resonance parameters were estimated for each data section after obtaining the tidal parameters of mainly diurnal tidal waves. The correlation of the time variation in diurnal tidal waves and FCN period was discussed. For comparison, a similar method was used to analyze VLBI observations to study the time variability of nutation terms and FCN period. The variation trend of the FCN period totally depends on the Ψ1 wave in tidal gravity and on the retrograde annual term in nutation. We observed a similar variation trend in the FCN periods obtained from different SG stations worldwide and VLBI observations. The relation between diurnal tides and LOD variations is discussed and the possible mechanisms of the decadal variation in FCN periods were discussed. 相似文献
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本文应用中国大陆两条经度链和两条纬度链上共37个地电场台站的观测数据,研究了地电场日变化的时/频域特征,结果认为,绝大多数台站的日变化表现为两次起伏的半日波,紧临午前午后出现;按FFT振幅谱由大到小,其主要周期成分依次为12.4/12、8、24 h等,与潮汐调和分量周期一致;纬度效应主要表现为沿经度链的日变化幅度与纬度高/低有关,日变化相位差与当地时差吻合;Loyd季节的J季节日变化幅度最大、E季节其次、D季节最小.讨论了产生日变化主要周期成分的可能原因,认为月日引潮力引起的地面涡旋电流强度变化和太阳风引起的空间电磁活动共同产生了地电日变化的半日波周期成分. 相似文献
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William P. O'Connor 《Pure and Applied Geophysics》1976,114(6):933-943
Summary The atmospheric electric potential gradient was recorded continuously by a field mill at Fargo, North Dakota, for the period August, 1972–March, 1973. Hourly averages were taken by the equal areas technique to eliminate short period variations. The diurnal variation of monthly averages is shown for the fair weather periods and all weather. In addition, the diurnal variation is shown for all positive values of the potential gradient, which excludes periods of major local space charge generators, but includes periods when the potential gradient might be influenced by regional conditions not otherwise present during fair weather. For a given month the diurnal variation curves are generally similar, with the fair weather curve giving the highest values, and all weather curve giving the lowest values. The months September–November have similar curves with the lowest values and least deviation from the average. The months December–February have similar curves with the highest values.Harmonic analysis is used to compute the times of maxima and contributions to variance of the first four harmonics for each diurnal variation curve. The fair weather first harmonic accounts for the majority of variance and has a maximum near 19.5 h GMT. It is attributed to the global diurnal variation of potential gradient due to thunderstorm activity in the tropics. The second harmonic has one maximum occurring from 9–12 h local time and is attributed to the austausch effect of convection, where ions affect the conductivity of the air locally.The differences in these monthly diurnal variation curves emphasize that the season of year, weather conditions, and length of time over which data is averaged must be specified in atmospheric electricity studies if meaningful conclusions are to be drawn. 相似文献
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结合同台观测的水平地电场数据,研究坪城垂直地电场观测数据,结果表明:(1)采用固体不极化电极进行垂直地电场观测,同一极距的观测结果基本一致,而铅板电极与固体不极化电极之间存在较大的电位差;(2)垂直地电场日变化形态清晰,长极距测道(A1C1、A2C1和A3C1测道)日变幅为5.85 mV/km左右,短极距(B1C1、B2C1和B3C1测道)日变幅为10.02 mV/km左右;(3)垂直向观测的地电场日变化优势周期在12 h和24 h。 相似文献
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利用新建中山站高频雷达2010年4月到2011年2月的观测数据,研究了中山站高频雷达回波的日变化特征以及地磁活动的影响. 研究结果表明,中山站高频雷达回波具有明显的日变化特征且受地磁活动影响较大. 雷达回波发生率的峰值在地磁活动较小时处于日侧;随着地磁活动的增强,峰值减小并向夜侧移动. 另外,平均多普勒视线速度具有明显的昼夜分布,夜侧主要为正向速度,即朝向雷达,日侧主要为负向速度,即远离雷达;随着地磁活动的增强,平均回波强度和平均多普勒视线速度的峰值都会增加,而多普勒谱宽则会减小. 相似文献
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Parts of the consecutive apparent resistivity monitoring stations of China have recorded clear diurnal variations. The relative amplitudes of diurnal variations at these stations range from 1.3‰ to 5.8‰. The daily accuracies of apparent resistivity observation are better than 1‰, because the background electromagnetic noise is rather low at these stations. Therefore, the diurnal variations of apparent resistivity recorded at these stations are real phenomena. The diurnal variation shapes can be divided into two opposite types according to their characteristics. One type is that the apparent resistivity data decreases during the daytime but increases during the nighttime(Type 1). The other type is the apparent resistivity data increases during the daytime but decreases during the nighttime(Type 2). There is a correspondence between the diurnal and annual variation patterns of apparent resistivity. For the monitoring direction with diurnal variation of Type 1, the apparent resistivity decreases in summer and increases in winter. However, for the monitoring direction with diurnal variation of Type 2, the apparent resistivity increases in summer and decreases in winter.
We take an analysis on the mechanism of apparent resistivity diurnal variation, combining the influence factors of water-bearing medium's resistivity, the electric structure of stations, and the apparent resistivity sensitivity coefficient(SC)theory. Intuitively, diurnal variation of apparent resistivity is caused by diurnal variation of medium resistivity in the measured area. The diurnal variation of medium resistivity will inevitably be caused by the factors with diurnal variation. Among the possible factors, there is diural variation in earth tide and temperature.
Our analysis displays that apparent resistivity diurnal variation is not caused by the usually-believed earth tide, but by the ground temperature difference between daytime and nighttime. The earth tide strain is too small to cause remarkable effects on the apparent resistivity data. On the other hand, the daily tide strain has two peak-valley variations, and its phase and amplitude has a period of approximate 28 days. However, the apparent resistivity data do not show these corresponding features to earth tide. Furthermore, the detection range of current apparent resistivity stations is within a depth of several hundred meters. Within this depth range, the medium deformation caused by solid tide can be regarded as uniform change. Therefore, all monitoring directions and all stations will have the same pattern of diurnal variation.
In general, the temperature increases in the daytime but decreases in the nighttime. For most water-bearing rock and soil medium, its resistivity decreases as temperature increases and increases as temperature decreases. Diurnal temperature difference affects about 0.4m of soil depth. Therefore, resistivity of this surface thin soil layer decreases in the daytime while increases in the nighttime. Under layered medium model, SC of each layer represents its contribution to the apparent resistivity. For the stations with positive SC of surface layer, apparent resistivity decreases in the daytime but increases in the nighttime. While for the stations with negative SC of surface layer, apparent resistivity diurnal variations display the opposite shape. 相似文献