共查询到19条相似文献，搜索用时 218 毫秒
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《地震地磁观测与研究》2016,(6)
通过将廊坊、富克地磁台站数据与国内地磁台站十三陵、三亚台以及国际标准地磁台站MMB台的观测数据对比分析,发现各地磁台站数据变化幅度相近、相关性高,对地磁暴有明显响应,且磁暴期间各时段扰动幅度相近。同时,以高质量地磁数据为基础,采用快速傅里叶变换,对廊坊与富克地磁台站的地磁观测数据开展地磁脉动提取,研究发现,两个台站在地磁暴期间均能观测到明显的Pi1、Pi2、Pc5地磁脉动,且Pc5的持续时间、平均强度、变化幅度和Pi1的持续时间、变化幅度及Pi2的变化幅度均有明显增加,为今后开展地磁脉动与高能电子增强事件相关性研究奠定了基础。 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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本文利用低纬地磁台站的Pi1、Pi2地磁脉动（Pi1-2）资料和地球同步轨道的Pc5地磁脉动资料,对2004年1月到2006年12月38个磁暴事件的地磁脉动参数进行了统计分析.在此基础上,考虑相对论电子的局部加速机制,并加入损失机制,建立了一个初步的磁暴期间地球同步轨道相对论电子通量对数值的预报模型.利用该模型,我们对上述38个磁暴事件进行预报试验,最优化结果是：相对论电子通量对数值的预测值和观测值之间的线性相关系数为0.82,预报效率为0.67.这说明该模式具有较好的预报效果,也表明利用地磁脉动参数进行相对论电子通量预报是可行的. 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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亚暴期间磁尾等离子体片离子注入内磁层能够激发电磁离子回旋(EMIC)波.对应于这种EMIC波,地面磁力仪可观测到周期逐渐减小的地磁脉动(IPDP).利用GOES卫星数据,地磁指数和加拿大CARISMA地磁台站的数据,我们研究了IPDP事件的产生与亚暴磁尾注入的关系.同时利用CARISMA地磁台链中的MCMU和MSTK两个台站,从2005年4月到2014年5月期间的观测数据,统计分析了亚暴期间的IPDP事件,研究了IPDP事件的出现率关于季节和磁地方时的分布特征.我们总共获得128个两个台站同时观测的IPDP事件.该类事件关于季节分布的发生率,冬季最小,为13.28%,春季最大,为32.81%,结果表明IPDP事件关于季节分布的发生率受到电离层电导率及亚暴发生率的影响.两个台站同时观测到的IPDP事件最大出现率出现在15—18 MLT(磁地方时),结果表明IPDP事件主要由亚暴期间产生的能量离子注入内磁层,西向漂移遇到等离子体层羽状结构(Plume)区的高密度等离子体所激发. 相似文献
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本文分析了1988年12月和1989年1月在长春、北京、兰州3个台站上观测的地磁脉动资料,研究了3个台站同时记录到的Pi2地磁脉动的频谱特征和偏振特性,进而对低纬Pi2地磁脉动的产生和传播机制做了理论研究. 相似文献
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研究了2001年11月14日昆仑山MS8.1大地震前新疆地区宽频带地震仪记录到的异常扰动事件.新疆地震台网在发生强震的前三天记录到了强烈的扰动信号.由于新疆地震台距离昆仑山大地震的震中很近,因此该震前扰动的成因备受关注,一直被认为可能是与大地震相关的慢地震事件,可能是大地震的某种前兆现象.本研究扩大了观测异常扰动事件的范围,分析了欧亚大陆187个宽频带地震仪在2001年11月的观测记录,发现这些地震仪在11月10—12日期间都记录到了时频特征类似的强扰动信号,其中最强的扰动信号出现在挪威台站KONO.调查研究发现挪威海域在11月10—12日期间出现了一次超强北极风暴,我们对扰动源位置初步定位后发现大地震前欧亚大陆各台站记录的最大扰动信号主要来源于挪威西南海岸.本文的研究结果确认昆仑山大地震前新疆台网记录到的强烈震前扰动信号不是与大地震相关的慢地震事件,而是挪威海域北极风暴激发的微地震（地脉动）.本文进一步研究表明北极风暴激发的地脉动可显著影响中国大陆的地震和重力观测.在分析中国大陆地震台网记录的强扰动信号时,北极风暴的影响不能忽视. 相似文献
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依托“中国地震数据观测网络”项目,中国地震局地震预测研究所建立了以十三陵地震中心台为前兆台网部,8个无人值守的前兆台站为一体的前兆观测系统。 这套系统利用中国联通的CDMA 1X网络将台站接入到Internet网络,并利用VPN(Virtual Private Network)技术在Internet网络上开辟一条安全、 稳定传输隧道,实现了前兆台站、 观测设备与十三陵前兆台网部的信息集成。 文中以十三陵地震前兆观测系统为例,主要介绍了如何利用CDMA 1X 无线网络和VPN(Virtual Private Network)技术实现前兆观测系统信息集成。 十三陵地震前兆观测系统的正常运行证明,利用CDMA 1X +VPN技术的前兆观测系统组网模式可以做到投资少、 见效快、传输可靠等优势,值得推广应用。 相似文献
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We conducted a statistical analysis of the physical characteristics of the micropulsation activity (Pc3 and Pc4 range) detected, during the austral summer 1994/95, at Terra Nova Bay (Antarctica, corrected latitude 80.0°S), a station which is few degrees poleward of those where most of the Antarctic measurements in these frequency ranges have been performed. The emerging overview suggests that the correspondence between the pulsation power and the external parameters (solar wind speed, interplanetary magnetic field magnitude and orientation) is significantly stronger than at somewhat lower latitudes. The day-to-day power variability was found to be strictly related to the general level of the geomagnetic activity, and the power level sharply maximizes at local magnetic noon. In the Pc4 range peaks of correlation with the SW speed are found in the dawn and dusk sides of the Earths magnetosphere and the daily variation of the polarization pattern is closely consistent with that found at auroral latitudes and at lower frequencies. In the Pc3 range the correlation coefficient between the pulsation power and the SW speed has maximum values in the local morning, and the frequency of selected events reveals a strong IMF control during closed magnetospheric conditions. The local time dependence of the correlation coefficient between the pulsation power and the cone angle reveals an additional control by the IMF orientation, which becomes more explicit around local noon. 相似文献
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G. Chisham D. Orr T. K. Yeoman D. K. Milling M. Lester J. A. Davies 《Annales Geophysicae》1995,13(2):159-167
In this study over 100 Pc5 events observed on the SAMNET magnetometer array have been catalogued. The ground horizontal polarization of these waves has been investigated and it has been shown that there are large differences between the polarization azimuth distributions on either side of noon. In the morning the azimuth distributions are spread evenly across all possible orientations whereas in the afternoon they are predominantly in a North-South orientation. The difference appears to be the result of a specific polarization pattern that occurred across the SAMNET array for 31 of the Pc5 events. These 31 Pc5 events all occurred in the morning sector, close to the dawn terminator. It is suggested that this special polarization pattern is a consequence of ionospheric conductivity gradients that occur at around dawn. This theory is reinforced by the comparison of the local times of these polarization variations with the local time of sunrise. By employing ionospheric conductivity data from the EISCAT radar for two of these Pc5 events, this connection has been studied in more detail. 相似文献
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《Journal of Atmospheric and Solar》2007,69(14):1759-1764
The analysis of 85,800 events (1979–1981) of Moscow ambulance calls, related to the myocardial infarction (MI), demonstrates a seasonal variation with the profound summer minima and winter maxima. Similar results were obtained by analyzing the 25-year (1970–1995) statistical monthly data on the death from infarction in Bulgaria. The estimated high correlation coefficient (0.84) between Moscow and Bulgarian data suggests a common reason. There is a great number of clinical and statistical studies confirming that the MI number rises during geomagnetic disturbances, which have a maximum of occurrence near equinox, not in winter. In order to explain this contradiction we suggest that one of the critical additional factors, which affect a human cardiovascular system, could be geomagnetic Pc1 pulsations at frequencies comparable with the human heart beat rate. The MI variations as well as the Pc1 pulsations exhibit a summer minimum. The comparative analysis of the Moscow ambulance MI data and Pc1 pulsations recorded at the geophysical observatory in Borok is presented. It is shown that in about 70% of the days when an anomalously great number of ambulance calls (AMI) has been registered Pc1 pulsations have been recorded. In the winter season the probability of the simultaneous AMI and Pc1 occurrence was 1.5 times larger than their accidental coincidence. Moreover, it was found that the effects of magnetic storms and Pc1 in AMI were much higher in winter than in summer. We suggest that the seasonal variation of the production of the pineal hormone melatonin leads to a winter instability in the human organisms and increases the sensitivity of the patient to the “negative” influence of Pc1 geomagnetic pulsations in winter. 相似文献
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Summary A local planar approximation of a stratified, inhomogeneous, anisotropic and dissipative ionosphere is presented as an Alfven
quarter-wave plate resonator in the Pc1 micropulsation range. The frequency-amplitude structure of the resonance response
of an isotropic Alfven wave on the Earth's surface and at a given altitude in the ionosphere is studied in comparison to standing
waves in vacuum above an ideal conductor for a particular model of the ionosphere. An asymmetry in the response was found
at both boundary of the resonator, at the Earth's surface and at the given altitude z0. The results are related to the vertical changes of frequency dispersion in the dissipative medium of the ionosphere and
to the vertical profile of the inhomogeneities of the resonator being considered. 相似文献
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Summary The spectral analysis of an hourly section of a synchronized conjugated record of an ULF signal made on the GEOS-1 satellite and the Husafell Observatory (Iceland) on July 13, 1977, has been carried out. The time variations of the spectral frequency-amplitude characteristics of the Pc1 wave packet in the neighbourhood of f 0.5 s–1 at both measurement sites were examined. The transmissibility of the amplitude of the total magnetic component of the wave through the ionosphere towards the Earth's surface, found in the frequency range of the packets, varies from 0.03 to 0.07. Moreover, its time behaviour with the development of the micropulsation disturbance was studied. The frequency shift of the packet spectrum centre towards higher frequencies 0.04 s–1) was determined at the Earth's surface as compared with the satellite conditions. Experimental results served to test the developed automated methods of numerical modelling of ionospheric filtration in the ULF range of Pc1 micropulsations. Good agreement between the experimental and numerical results of the two constructed limiting models of the daytime ionosphere at higher latitudes (low and high solar activity) was achieved. The values of the transmissibility calculated for the Pc1 packet frequencies vary from 0.075 to 0.3 and from 0.025 to 0.06. 相似文献
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In this paper case studies of propagation characteristics of two TIDs are presented which are induced by atmospheric gravity waves in the auroral F-region on a magnetic quiet day. By means of maximum entropy cross-spectral analysis of EISCAT CP2 data, apparent full wave-number vectors of the TIDs are obtained as a function of height. The analysis results show that the two events considered can be classified as moderately large-scale TID and medium-scale TID, respectively. One exhibits a dominant period of about 72 min, a mean horizontal phase speed of about 180 m/s (corresponding to a horizontal wavelength of about 780 km) directed south-eastwards and a vertical phase speed of 55 m/s for a height of about 300 km. The other example shows a dominant period of 44 min, a mean horizontal phase velocity of about 160 m/s (corresponding to a horizontal wavelength of about 420 km) directed southwestwards, and a vertical phase velocity of about 50 m/s at 250 km altitude.Max-Planck-Institut für Aeronomie, Germany. On leave from Department of Space Physics, Wuhan University, China 相似文献
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《Journal of Atmospheric and Solar》2007,69(14):1753-1758
This paper deals with the problem of human impact on the electromagnetic environment of the Earth. We have focused our attention on the Pc1 electromagnetic waves (the frequency range is 0.2–5 Hz), which are spontaneously excited due to the instability of magnetospheric plasma. This paper describes the analysis of the long-term ground-based Pc1 observations to search for the so-called weekend effect, or, more generally, a specific weekly cycle in the Pc1 wave activity. It is supposed that such effects are evident of human origin. The data on the Pc1 occurrence at Borok (Φ=54.05°, Λ=119.44°, L=2.9) in 1958–1992 are examined. The synchronous detection method in the form of superposition epoch analysis has been used. It was found statistically that there is an inherent difference of about 10% in the numbers of Pc1 wave trains between weekdays and weekends. The main conclusion is that the weekly cycle in the Pc1 wave activity is a real geophysical phenomenon. 相似文献
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In the past slow-speed frequency-modulated analogue tape recording techniques have provided the most convenient method for recording ground-based Pc1 pulsation data on a continuous basis. With events occurring often only a few hours in a week, and a Nyquist frequency of 4–5 Hz, direct digital recording is not practical because of the bulk of data accumulated. However, with the recent availability of reasonably priced microcomputers and advanced signal processing techniques it is now possible to preprocess digital data in the field and store only events of interest. A two-component induction coil magnetometer incorporating a Z80 based 64K RAM microcomputer-floppy disk preprocessing system is described. It is capable of recording Pc1 signals in the 0.2–4 Hz band at middle-to-low latitudes with a minimum detectable signal level of 3 pT. The reliability and limitations of the preprocessing techniques utilizing FFT autospectral analysis to recognize Pc1 signals are discussed. 相似文献