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1.
Summary The method of spectral analysis has been modified to render the spectrum not only a function of frequency, but also of damping. The generalized spectra of damped geomagnetic pulsations, recorded at the observatories of Budkov and Dymer, are computed. The degree of damping of these pulsations in the X and Y-components at both stations is determined. The results are compared with results obtained using other methods. 相似文献
2.
A local approximation method based on piecewise sinusoidal models has been proposed in order to study the frequency and amplitude characteristics of geomagnetic pulsations registered at a network of magnetic observatories. It has been established that synchronous variations in the geomagnetic pulsation frequency in the specified frequency band can be studied with the use of calculations performed according to this method. The method was used to analyze the spectral–time structure of Pc3 geomagnetic pulsations registered at the network of equatorial observatories. Local approximation variants have been formed for single-channel and multichannel cases of estimating the geomagnetic pulsation frequency and amplitude, which made it possible to decrease estimation errors via filtering with moving weighted averaging. 相似文献
3.
Pc3 geomagnetic pulsations at near-equatorial latitudes at the initial phase of the magnetic storm of April 5, 2010 总被引：1，自引：0，他引：1
N. G. Kleimenova N. R. Zelinskii O. V. Kozyreva L. M. Malysheva A. A. Solov’ev Sh. R. Bogoutdinov 《Geomagnetism and Aeronomy》2013,53(3):313-320
An analysis of sampled 1-s observational data on geomagnetic pulsations within the Pc3 range on the INTERMAGNET network of near-equatorial and low-latitude observatories spaced over longitude during the initial phase of a moderate magnetic storm (April 5–7, 2010) was carried out for the first time. The obtained results were compared with magnetic observations at the low-latitude Chambon-la-Foret (CLF) and subauroral Kerguelen (PAF) observatories, as well as with observations at six Australian observatories located at low and middle latitudes. Two time intervals were studied in detail: the sudden commencement (SC) of the storm and the onset of the great global substorm. In the first interval, maximal amplitudes of near-equatorial pulsations were observed in the near-noon sector; in the second interval, in the near-midnight sector. The dynamics of the spectral structure of Pc3 pulsations in the considered events was shown to be different in spite of the fact that in both cases an amplification of waves was observed in two close spectral bands of the Pc3 spectrum: ～20–30 and ～30–40 mHz. The considered Pc3 pulsations were characterized by very small azimuthal wavenumbers (0.5 and less). Possible generation mechanisms for the observed Pc3 pulsations are discussed. 相似文献
4.
J. Ver H{o} I. Best M. Vellante H. Lühr M. de Lauretis L. Holló F. Märcz J. Str ues utik 《Annales Geophysicae》1995,13(7):689-697
Using data on the occurrence frequency of geomagnetic pulsations of different periods from three observatories in Central Europe, conclusions are drawn about the occurrence of field line resonances and pulsations directly driven by upstream waves at L-values below 3. It was found that both types occur during the interval studied (first 6 months of the year 1991), but both the occurrence frequency of the two types and the characteristic period of the field line resonance change significantly as compared to other intervals. During Northern winter, pulsation activity is severely damped in solar maximum years, including the year 1991. The decrease in the activity of the pulsations is more significant at shorter periods. 相似文献
5.
通过若干实例,本文讨论了地磁数据分析中的一些方法.这些方法包括时间序列的多项式拟合,相关性分析,频谱分析和小波分析等.在Matlab和AutoSignal软件下实现了以上方法,并基于这些方法研究了地磁场形态和地磁现象的频谱特征.我们分析了Surlari观测台（余纬45.3°,经度26.3°）的地磁时间序列,并与Ottawa（余纬44.6°,〖JP2〗经度284.5°）,Canberra（余纬125.3°,经度149.3°）, Kakioka（余纬53.8°,经度140.2°）,Vernadsky〖JP〗（余纬155.3°,经度295.7°）等台站的结果进行了对比分析,讨论了Fourier变换时间窗和小波基函数选取的影响,有限长时间序列引起的边缘效应,以及小波尺度和Fourier频率的关系等问题.我们采用谱分析和小波分析处理了2007年两个台站的地磁数据,研究了地磁场形态和地磁现象的频谱特征,并讨论了Fourier变换和小波变换的优缺点. 相似文献
6.
Karel Prikner Jaroslay Střeštík Karel Dobeš Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1973,17(4):337-345
Summary Using the method of two-component spectral analysis of planar oscillation events by means of computer processing of A-t records, a series of about 100 samples of geomagnetic beating-type pulsations pc3 was treated. The quantitative data obtained on the internal structure of the pulsations (frequency spectra and polarization characteristics) were treated statistically. The pattern of the daily variations of the frequencies and amplitudes of the fundamental amplitude-dominating frequency components of the pulsations and the daily variations of the polarization characteristics of these components, the ellipticity of the polarization ellipses, the directions of the main axes of these ellipses and the sense of rotation of the disturbance vector along the ellipses were obtained.A part of the results was reported at the XVth General Assembly of the IUGG, Moscow, August 1971. 相似文献
7.
The characteristics of 80 geomagnetic storm spectra have been analyzed and compared for the records at seven observatories:
Beijing, Qingguang, Changli, Guangzhou, Sheshan, Wuchang and Changchun during 1973–1977. The general natures of the spectra
are thus obtained. The results are as follows. First, there are synchronous trends of change in the magnetic storm spectral
amplitude at the seven observatories. Second, the sepctral slopes of all the magnetic storms are almost the same. The yearly
average values of the spectral slopeb are quite steady within the period range from 0.5 to 6.8 hours. This means that the magnetic storms have the same energy
partitioning factor. Third, there are significant changes in the yearly average values of spectral interceptsa for the three observatories of Beijing, Qingguang and Changli which are near the Tangshan earthquake area, but the values
are quite steady for the four observatories of Guangzhou, Sheshan, Wuchang and Changchun which are far from the earthquake
area. It seems that the noticeable changes are related to the great Tangshan earthquake of July 28, 1976. 相似文献
8.
In the framework of the program for setting the Callisto spectrometer network into operation, the spectral measurements were
carried out at the sites of spectrometer locations in India and Russia in winter 2006. The results achieved at Badary, the
site where the Siberian Solar Radio Telescope (SSRT) is located, are presented. The measurements were performed using a broadband
log-periodic antenna connected to the Callisto spectrometer developed at the Institute of Astronomy (Zurich). The results
of these measurements should explain whether spectral studies at frequencies below 1 GHz can be performed using such antennas
or new antennas should be developed. The presented results are compared with the similar results obtained in Switzerland in
the frequency intervals of interest for radio astronomy. Concerning electromagnetic noise, Badary is a better site for observing
the Sun in the 50–800 MHz frequency range as compared to observatories in Switzerland. 相似文献
9.
本文对北京、青光、昌黎、广州、佘山、武昌、长春等7个地磁台1973——1977五年期间80个磁暴的振幅谱进行了分析和对比,得到中低纬度地区磁暴频谱的一般特性.结果表明:①7个台磁暴频谱的变化趋势同步;②在周期0.5——6.8小时的频率范围内,振幅谱的斜率 b 值相当稳定,反映了在此频段内磁暴能量具有恒定的分配因子;③广州、佘山、武昌、长春四台振幅谱截矩 a 的年均值相当稳定,而距唐山震区较近的北京、青光、昌黎三台 a 的年均值均有不同程度的显著变化.这可能与1976年7月28日强烈的唐山地震有关. 相似文献
10.
The influence of the homogeneous and inhomogeneous ionosphere on the orientation angle of the horizontal magnetic vectors of the long-time geomagnetic pulsations is under consideration in this study. It was realized that this angle is small in the case of the homogeneous ionosphere for both the Alfvén and magnetosonic types of oscillations. An increase in the ionospheric electric field was discovered as the ionospheric conductivity changes during the switch from day to night conditions. It is valid only for the initial Alfvén wave. The ionospheric equivalent current systems excited by the initial magnetospheric waves of Alfvén and magnetosonic types as well as their behavior near the terminator were studied for different seasons. For the Alfvén source, seasonal variations of the orientation angle close to sunrise at the equator depend on the type of source: odd or even modes of Alfvén oscillations excite observable pulsations. It was found that the ionospheric two-vortex equivalent current system of the long-period pulsations arising in high-latitudes in the equatorial region alters not only its direction, but its intensity too. The largest anomaly (\sim25% of the source value) would be expected near the terminator. A new experimental method was suggested to recognize the type of incident magnetospheric waves by implementing observations either at a single observatory or at a couple of observatories. In the case of a single observatory it is proposed to study the frequency dependence of the orientation angle of their magnetic components close to sunrise. If the initial wave is magnetosonic, this angle must not be changed as a function of the local time within the wide frequency range of pulsations. When pulsations have an orientation angle sensitive to the presence of the terminator, they may be classified as both Alfvén and magnetosonic. For the Alfvén waves no frequency dependence of the orientational angle is peculiar. On the contrary, magnetosonic waves should be determined as oscillations with an orientational angle proportional to the frequency. These oscillations may be revealed at observatories located on the high-resistance cross sections. The example of the spectral-temporal analysis of pulsation at the equatorial observatory in Huancayo was demonstrated to confirm the proposed experimental technique. A weak dependence of the orientation angle anomaly on the frequency near the terminator was found. The latter is evidence for the dominant contribution of the Alfvén waves to low-latitude and equatorial oscillations. 相似文献
11.
Identification and classification of transient pulses observed in magnetometer array data by time-domain principal component analysis filtering 
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下载免费PDF全文 A method for identification of pulsations in time series of magnetic field data which are simultaneously present in multiple channels of data at one or more sensor locations is described. Candidate pulsations of interest are first identified in geomagnetic time series by inspection.Time series of these ‘‘training events' ' are represented in matrix form and transpose-multiplied to generate timedomain covariance matrices. The ranked eigenvectors of this matrix are stored as a feature of the pulsation. In the second stage of the algorithm, a sliding window(approximately the width of the training event) is moved across the vector-valued time-series comprising the channels on which the training event was observed. At each window position, the data covariance matrix and associated eigenvectors are calculated. We compare the orientation of the dominant eigenvectors of the training data to those from the windowed data and flag windows where the dominant eigenvectors directions are similar. This was successful in automatically identifying pulses which share polarization and appear to be from the same source process. We apply the method to a case study of continuously sampled(50 Hz) data from six observatories, each equipped with threecomponent induction coil magnetometers. We examine a90-day interval of data associated with a cluster of four observatories located within 50 km of Napa, California,together with two remote reference stations-one 100 km to the north of the cluster and the other 350 km south. When the training data contains signals present in the remote reference observatories, we are reliably able to identify and extract global geomagnetic signals such as solar-generatednoise. When training data contains pulsations only observed in the cluster of local observatories, we identify several types of non-plane wave signals having similar polarization. 相似文献
12.
Geomagnetic pulsations of the serpentine-emission (SE) type are considered. A method for estimating the frequency and amplitude parameters in the form of a time function for pulsations—SE and the accompanying spectral components—is suggested. An estimation algorithm is developed on the basis of local approximating polyharmonic models and weighted moving average filtration. Examples of the estimation of the frequency and amplitude parameters of SE pulsations are given. It is proposed that the procedure be used to calculate the estimation errors in SE pulsation frequency parameters and to choose the tuning parameters. 相似文献
13.
Spatial-temporal and spectral features of ground geomagnetic pulsations in the frequency range of 1–5 mHz at the initial phase of a strong magnetic storm of the 24th cycle of solar activity (August 5–6, 2011, with a Dst-variation in the storm maximum of ?110 nT) are analyzed. Large opposite in sign amplitudes of variations in IMF parameters (from ?20 to +20 nT) at a high velocity of the solar wind (～650 km/s) accompanied by intense bursts in solar-wind density (up to ～50 cm?3) were distinctive feature of interplanetary medium conditions causing the storm. Geomagnetic Pi3 pulsations global in longitude and latitude and in-phase in the middle and equatorial latitudes were found. The onset of pulsation generation was caused by a pulse of dynamic pressure of the solar wind (～20 nPa), i.e., by a considerable compression of the magnetosphere. The maximum (2–3 mHz) in the amplitude spectrum of near-equatorial pulsations coincided with the maximum of pulsations in the daytime polar cap. After the next jump of the dynamic pressure of the solar wind (～35 nPa), an additional maximum appeared in the pulsation spectrum in the frequency band of ～3.5–4.5 mHz. Global pulsations suddenly stopped after a sharp decrease in the solar-wind dynamic pressure and corresponding extension of the magnetosphere. The obtained results are compared with the time dynamics of the position and shape of the plasmapause. 相似文献
14.
The solar eclipse on August 11, 1999, observed in the region covered by many geomagnetic observatories, has offered a unique opportunity to look for an effect of the eclipse on geomagnetic pulsations. The pulsation activity digital data have been taken from Budkov Observatory in the Czech Republic (in the X component only), from observatories in Germany (Niemegk, Fürstenfeldbruck, Bad Bergzabern), in Hungary (Nagycenk), and for comparison in South Africa (Hermanus, conjugate-point station), and in Finland (Sodankylä, far from the eclipse zone). At all these stations the field in all three component has been recorded. The pulsation amplitudes in the X component exhibit a long-term minimum near the time of the eclipse. Spectral analysis of selected short intervals confirmed this decrease and also revealed a decrease of the average pulsation period during the eclipse. Such a change in the amplitude or in the period was not observed outside of the eclipse interval or in other days. Investigation in some narrower frequency bands showed that the maximal decrease occurred in the 15–20 s band. All these changes can be found in records from all the stations near the eclipse totality belt, also in records at the conjugate-point station, where no eclipse occurred. No signature has been found in records at the station situated far from the eclipse zone. 相似文献
15.
Summary A method of numerical simulation of the coefficient of reflection of the ionospheric transition layer as a function of frequency is applied to the experimental data related to several series of pearl-type pulsations Pc1 (f = 0.2 – 2 Hz) recorded at the observatories of Kerguelen, Sogra and Nurmijarvi. The inverse problem of modelling, i.e. determining the vertical profiles of ionospheric electron concentration corresponding to the actual experimental situations, was solved approximately. The initial assumption for interpreting the specific nature of the series of Pc1 micropulsations parallel in time was their resonance origin under reflection of the signal at magnetically conjugate ionospheres, Alfvén's resonators, in both of the Earth's hemispheres. 相似文献
16.
Day-time Pc 3–4 (≃5–60 mHz) and night-time Pi 2 (≃5–20 mHz) ULF waves propagating down through the ionosphere can cause oscillations in the Doppler shift of HF radio transmissions that are correlated with the magnetic pulsations recorded on the ground. In order to examine properties of these correlated signals, we conducted a joint HF Doppler/magnetometer experiment for two six-month intervals at a location near L = 1.8. The magnetic pulsations were best correlated with ionospheric oscillations from near the F region peak. The Doppler oscillations were in phase at two different altitudes, and their amplitude increased in proportion to the radio sounding frequency. The same results were obtained for the O- and X-mode radio signals. A surprising finding was a constant phase difference between the pulsations in the ionosphere and on the ground for all frequencies below the local field line resonance frequency, independent of season or local time. These observations have been compared with theoretical predictions of the amplitude and phase of ionospheric Doppler oscillations driven by downgoing Alfvén mode waves. Our results agree with these predictions at or very near the field line resonance frequency but not at other frequencies. We conclude that the majority of the observations, which are for pulsations below the resonant frequency, are associated with downgoing fast mode waves, and models of the wave-ionosphere interaction need to be modified accordingly. 相似文献
17.
根据捷克和斯洛伐克电磁台站的数据 ,得到波西米亚块体地壳和上地幔的电阻率分布模型。估计电阻率时特别使用了短周期和长周期的电磁数据以及用连续谱方法对固定台站数据的分析结果。根据欧洲地磁感应矢量分布绘出了显著的地电不均匀带的地图 ,将波西米亚块体的视电阻率与中欧有关台站的感应标量长度与W1响应做了比较 ,并根据电阻率 /深度图估计了电导率范围 ,该图与替代性理想导体反演相对应 相似文献
18.
Ｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｒａｄｉａｔｉｏｎａｎｏｍａｌｉｅｓｂｅｆｏｒｅｍｏｄｅｒａｔｅａｎｄｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓ关华平，刘桂萍Ｈｕａ－ＰｉｎｇＧＵＡＮａｎｄＧｕｉ－ＰｉｎｇＬＩＵ（ＣｅｎｔｅｒｆｏｒＡｎａｌｙｓｉｓａｎｄＰｒｅｄ... 相似文献
19.
Summary The method of two-component spectral analysis is described in two versions: as the so-called static analysis, in which the pulsation sample being studied is treated as a whole, and as the dynamic analysis, in which the given sample is processed piecewise in order to determine the time variations of various parameters. Both versions were applied to geomagnetic pi2 pulsations. The pi2 oscillations are resolved into several frequency components. The properties of these components are studied in dependence on the frequency and local time. The time variation of the amplitude (attenuation) and the polarization characteristics (precession) of pi2's are also studied. 相似文献
20.
Jaroslav Střeštík Karel Prikner Karel Dobeš Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1973,17(1):27-35
Summary The spectra of nearly 100 samples of Bpc3 pulsations were computed in the X and Y components of data from the Budkov Observatory. These spectra were used to study the daily variations of the fundamental characteristics of the pulsations, the frequency f
0
and amplitude A
0
of the main spectral peaks. The daily variation of the ellipticity of the polarization ellipses of oscillations in frequency f
0
was also studied in the XY-plane.Part of these results was reported at the XVth General Assembly of the IUGG, Moscow, August 1971. 相似文献