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1.
Fractal theory is applied in a quantitative analysis of geomagnetic storms. Fractal dimensions (D) of the attractor for storm data from the Beijing observatory (40.0°N, 116.2°E) using several time intervals are calculated. A maximum value of 1.4 has been obtained for a geomagnetic storm; on quite days the dimension is only slightly larger than 0.5. Data from two storms are analyzed here. Results show that a combination of both D and the magnetic index, k, can perhaps describe the degree of solar disturbance better than the single parameter k.  相似文献   

2.
The relation of the maximal daily average values of the relativistic electron fluxes with an energy higher than 2 MeV, obtained from the measurements on GOES geostationary satellites, during the recovery phase of magnetic storms to the solar wind parameters and magnetospheric activity indices has been considered. The parameters of Pc5 and Pi1 geomagnetic pulsations and the relativistic electron fluxes during the prestorm period and the main phase of magnetic storms have been used together with the traditional indices of geomagnetic activity (A E, K p, D st). A simple model for predicting relativistic electron fluxes has been proposed for the first three days of the magnetic storm recovery phase. The predicted fluxes of the outer radiation belt relativistic electrons well correlate with the observed values (R ∼ 0.8–0.9).  相似文献   

3.
For at least 30 years now it has been well known that the Dst index can be modelled using the solar wind as input. Since then, many attempts have been made to improve the predictability of Dst using different approaches. These attempts are useful, for instance, to understand which features of the solar wind–magnetosphere interactions are most important in producing magnetospheric activity and how the Dst index would improve the space weather forecast. The Dst index is by far the most reliable and simple indication that a magnetic storm is in progress. In this work, the effect of using more than four magnetic stations and shorter time intervals than the hourly averages used in Sugiura's procedures is evaluated. The discussion is based on the results presented by Burton in 1975 and Feldstein in 1984 considering 4 or 12 magnetic stations and time averages of 2.5 min for a magnetic disturbed period that occurred from February 7–28, 1967, including two geomagnetic storms. The analysis has shown that the global representation of a magnetic storm by the standard Dst (Sugiura) is well preserved either using 4, 6, 12 magnetic stations or using 1 h, 2.5 min 1 min averages. A brief review of the current understanding of Dst has been included to support the discussions. The analysis performed has shown that a more refined Dst index (time and number of stations>4) would be useful to investigate the intrinsic processes and the different current systems involved in the ring current development during magnetic storms; the standard Dst, as it is conceived, is quite adequate to monitor geomagnetic storms and identify their overall features; concerning the magnetic stations normally considered, the inclusion of higher magnetic latitude stations (>35) may underestimate the observed Dst.  相似文献   

4.
The search for the magnetic precursors of earthquakes by the method of synchronous detection is described. The data of the Guam Observatory (13.6°N, 144.9°E) located in a seismically active region and the USGS/NEIC catalogue of the National Earthquake Information Center of the U.S. Geological Survey for the period from 1991 to 2009 are used. Earthquakes with magnitudes M ≥ 7 in the range of longitudes from 100° to 170°E are analyzed. The intervals of accumulation cover 40 hours before and 40 hours after an earthquake. The preliminary result reveals an enhancement of fluctuations in the Z-component within 12 hours before the earthquake.  相似文献   

5.
It is shown in a joint analysis of ionospheric vertical sounding data at the arctic Heiss Island and antarctic Vostok stations and the geomagnetic PC index, which characterizes the geoefficient component of the interplanetary magnetic field, that, during a disturbed geomagnetic period when PC > 2 in years of solar activity (SA) maxima in the winter season, positive phases of ionospheric disturbances are predominantly observed. In the nighttime hours, an increase in the critical foF2 frequencies by a factor of 2–3 can occur. In a disturbed geomagnetic period at the PC > 1.5 level in the summer season, negative phases of ionospheric disturbances are mainly observed. In years of maximum and moderate SA, the decrease in foF2, as compared to their median values, happens at night (∼30%). In years of low SA, the decrease value is much lower. At a substantial decrease in the PC index level, in the region of the geomagnetic pole at the Vostok station, in some cases, a substantial increase in the electron density level in the F region occurs with a delay of 0.5 h. At the same time, a significant correlation (r = −0.57) is observed between variations in the PC index and foF2.  相似文献   

6.
The variations in the geomagnetic cutoff rigidity in Irkutsk, Alma-Ata, and Beijing in October–November 2003 were calculated using ground-based measurements of cosmic ray intensity from the worldwide network of stations and GOES spacecraft. The calculated variations in geomagnetic cutoff rigidity are presented together with D st variations of the geomagnetic field. The obtained results are compared to calculations performed using the Tsyganenko model of the magnetosphere.  相似文献   

7.
During magnetic storms (MS’s) in the ionospheric D region, changes in the electron density and corresponding effects on radiowave propagation are observed. The differences in manifestations of MS’s in the lower ionosphere are mainly caused by the time and spatial differences in precipitations of energetic electrons. It is shown that the observed differences in the effects of storms in the D region are related to the differences in the corresponding types of MS’s determined by the observed fluxes of energetic electrons (E ∼ 0.1–2 MeV) at L ≈ 3–8. The storm types are identified by changes in the geomagnetic ap and AE indices and the ap/Dst and AE/Dst ratios during the recovery phase of a storm.  相似文献   

8.
We present a study of peculiarities of the winter nighttime maximum in the critical frequencies f 0 F2 at mid-latitudes of the Asian region. The data of stations located at different longitudes and close latitudes have been used in the analysis: Novosibirsk (54.8°N, 83.2°E), Irkutsk (52.5°N, 104.0°E), and Khabarovsk (48.5°N, 135.1°E). It has been found that the nighttime maximum in f 0 F2 is observed after midnight (∼0200–0400 LT) and is a stable feature of the quiet ionosphere from the middle of October to the middle of March at low solar activity (SA) at all analyzed stations. This interval decreases with increasing SA. The difference between the maximal and minimal f 0 F2 values in nighttime hours is the largest in December–January, and its amplitude is almost independent of SA. Variations in the critical frequency of the h m F2 layer are inversely related to those in the height of the maximum. We have studied periods when the difference between the daytime and nighttime values of f 0 F2 is less than 2 MHz. The intervals of observations of such events at different longitudes do not coincide. No dependence of the winter nighttime maximum amplitude on magnetic activity has been found.  相似文献   

9.
The diurnal variations in the amplitude and parameters of polarization ellipses of the first Schumann resonance according to three magnetic field components, observed on December 1–10, 2007, at the Barentsburg and Lovozero observatories, have been studied. Ellipses have been constructed in the (H, D) and (H, Z) planes. The value of the minor axis, inclination of the major axis, ellipticity, and the rotation direction have been estimated. The vertical magnetic component of the Schumann resonance is three to four times as small as the horizontal component. The difference in the diurnal variations in the ellipse parameters between both observatories has been found. The effect can be caused by a difference in the Earth’s conductivity in the vicinity of the observatories and by conductivity anisotropy. The major axis inclination and ellipticity have semidiurnal components. The polarization vector mostly rotates from D to H in the horizontal plane and from Z to H in the vertical plane at both stations.  相似文献   

10.
Based on large set of observational data (for ∼100 years), it has been demonstrated that the air temperature at midlatitudes in the years close to solar activity maximum is on average higher than in other years by DT = 0.11–0.15 degrees at many meteorological stations. The DT parameter is negative and smaller in magnitude near the equator and poles. A correct (in the energetic sense) physical mechanism by which solar and geomagnetic activities affect the ground level air temperature has been proposed.  相似文献   

11.
A complex of geophysical phenomena (geomagnetic pulsations in different frequency ranges, VLF emissions, riometer absorption, and auroras) during the initial phase of a small recurrent magnetic storm that occurred on February 27–March 2, 2008, at a solar activity minimum has been analyzed. The difference between this storm and other typical magnetic storms consisted in that its initial phase developed under a prolonged period of negative IMF B z values, and the most intense wave-like disturbances during the storm initial phase were observed in the dusk and nighttime magnetospheric sectors rather than in the daytime sector as is observed in the majority of cases. The passage of a dense transient (with N p reaching 30 cm−3) in the solar wind under the southward IMF in the sheath region of the high-speed solar wind stream responsible for the discussed storm caused a great (the AE index is ∼1250 nT) magnetospheric substorm. The appearance of VLF chorus, accompanied by riometer absorption bursts and Pc5 pulsations, in a very long longitudinal interval of auroral latitudes (L ∼ 5) from premidnight to dawn MLT hours has been detected. It has been concluded that a sharp increase in the solar wind dynamic pressure under prolonged negative values of IMF B z resulted in the global (in longitude) development of electron cyclotron instability in the Earth’s magnetosphere.  相似文献   

12.
A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the ＂2005.0 surface spline model of China geomagnetic field＂ created on the basis of the survey data with the ＂1970.0 surface spline model of China geomagnetic field＂, we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carded out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding ＂2005.0 partially revised surface spline model of China geomagnetic field＂. By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper.  相似文献   

13.
Analysis of Pc3 observational data along the 210° magnetic meridian showed a complicated frequency-latitude structure at middle latitudes. The observed period-latitude distributions vary between events with a “noisy source”: the D component has a colored-noise spectrum, while the spectrum of H component exhibits regular peaks that vary with latitude, and events with a “band-limited source”: the spectral power density of the D component is enhanced at certain frequencies throughout the network. For most ULF events a local gap of the H component amplitude has been exhibited at both conjugate stations at L ≃ 2.1. A quantitative interpretation has been given assuming that band-limited MHD emission from an extra-magnetospheric source is distorted by local field line resonances. Resonant frequencies had been singled out with the use of the asymmetry between spectra of H and D components. Additionally, a local resonant frequency at L ≃ 1.6 was determined by the quasi-gradient method using the data from nearly conjugate stations. The experimentally determined local resonance frequencies agree satisfactorily with those obtained from a numerical model of the Alfven resonator with the equatorial plasma density taken by extrapolation of Carpenter-Anderson model. We demonstrate how simple methods of hydromagnetic spectroscopy enable us to monitor simultaneously both the magnitude of the IMF and the magnetospheric plasma density from ULF data.  相似文献   

14.
Changes in the critical frequencies of the F2 layer at several midlatitude stations of ionospheric vertical sounding during a sharp depletion in atmospheric pressure under quiet solar and geomagnetic conditions are analyzed. It is shown that in such periods, the observed foF2 values differ from the mean values by approximately 10–15% and the deviations from the mean could be both negative (in the daytime hours) and positive (at night). Such variations in foF2 could be referred to the known class of ionospheric disturbances observed under a quiet geomagnetic situation, that is, to the so-called “Q-disturbances.” Analysis of wavelet spectra of foF2 variations shows the presence in the F region of oscillations of various periods (from 0.5 to 10 days). The decrease in the amplitude of daily variations during pressure depletion is found. Presumably, the observed effect is caused by the dynamic impact of waves formed in the lower atmosphere on the ionospheric F2 layer.  相似文献   

15.
The results of studying the distribution character of the amplitudes and time intervals between wave packets of Pi2 geomagnetic pulsations, observed during the nighttime development of magnetospheric substorms and in the absence of these phenomena, have been presented. The analog records from the midlatitude Borok Geophysical Observatory (geographic coordinates φ = 58.03°; λ = 38.97°) for 1995 and 1997 have been used to analyze Pi2 pulsations. Three groups of pulsations have been analyzed: Pi2 observed during sub-storms related to the external impact on the magnetosphere, Pi2 spontaneously originating during substorms, and Pi2 observed in the absence of substorms on the nightside of the magnetosphere. Interplanetary magnetic field B y and B z components and the solar wind dynamic pressure (ρV 2) have been considered as possible triggers of magnetospheric substorms. It has been indicated that the distributions of the amplitude and the duration of time intervals between Pi2 bursts are approximated by the power and exponential functions, respectively, which is typical of intermittent processes. The hypothesis that the processes of magnetospheric plasma turbulization can be among the Pi2 pulsation burst sources has been put forward. It is assumed that the obtained characteristic values can be used to qualitatively estimate the degree of plasma turbulence on the nightside of the magnetosphere when a sequence of Pi2 wave packets is excited.  相似文献   

16.
Using observational data of geomagnetic total intensity from 13 stations in the Beijing-Tianjin region, 3 stations in the western Yunnan region of China, and 6 stations in California of U. S. A., the daily variations and their spectra of geomagnetic total intensity were analyzed and compared. The results show that the morphology, the range and spectrum of daily variations in geomagnetic total intensity are basically the same within the local extent of 100–200 km and are different in the large extent of 500 km. The latitude factor of the daily variation range of geomagnetic total intensity is about 1–2 nT/degree within the latitude extent of 25°–40°. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 83–89, 1992. This work is supported by the State Seismological Bureau and the Chinese Joint Seismological Science Foundation, and U.S. Geological Survey.  相似文献   

17.
Variations of geomagnetic components X, Y, and Z recorded in 19 Intermagnet European observatories in 2004 were analysed. The original data from all observatories were preliminarily processed. In the first step, periods longer than three hours were filtered out. In the second step, variations of vertical geomagnetic component Z were separated into external and internal parts. We introduced a non-dimensional index η defined as the square root of a ratio of the energy of the external part of the vertical component to that of the horizontal components. Maps of the surface distribution of a new magnetic index η for the area of Europe at selected time periods were created, and their time changes are presented. The time changes of η for selected observatories are also shown. Moreover, we discuss a very interesting phenomenon we discovered, that has never been described in geophysical literature. Namely, in the recordings of all the observatories we noticed the presence of very regular variations, observed almost exclusively in the vertical component Z, which is quite unusual. These regular variations occur in the form of sinusoidal “wave packets”. The amplitudes of these variations do not depend on the geomagnetic latitude and appear in the records of all the observatories we analyzed. They occur in quiet days, which suggests that their source is in the ionosphere.  相似文献   

18.
Using the minute data of the H component of geomagnetic field from the 20°E magnetic meridian chain and the 30°N magnetic latitudinal chain, the temporal evolution characteristics of the equatorial ring current during the storm on November 7-10, 2004 are studied. It is indicated that the UT-MLT and UT-MLAT graphics extremely exhibit the local time distribution, latitudinal variation and temporal evo- lution of the H component. The results show: (1) The UT-MLT contour clearly shows the increasing of the H component mostly around noon during the initial phase, representing the geomagnetic effect from the magnetopause current system. During the main phase, most negative values of the H com- ponent appear around the dusk-side, indicating the dawn-dusk asymmetric distribution of the ring cur- rent. (2) The contour of UT-MLAT suggests the latitudinal variation of the H component decreasing with the enhancement of the latitudes during geomagnetic storm, which is in good agreement with the Dst index. The latitudinal variations provide a new sight for describing the temporal characteristics of the intensity of the storm-time ring current. (3) Both the contours of UT-MLT and UT-MLAT are useful to monitor the space-time distribution of the equatorial ring current.  相似文献   

19.
The features of the amplitude distributions of magnetic impulse events have been investigated using the observations from a number of high-latitude observatories in the Northern and Southern hemispheres. It has been shown that the tails of the statistical distribution functions of the impulse amplitudes are approximated by a power law of the form f(A) = A −α, where A is the impulse amplitude and α is the exponent. Therefore, the magnetic-impulse generation regime corresponds to the features of the on-off intermittency model. The distribution of the magnetic impulse amplitudes has been analyzed for various geomagnetic latitudes, local times, seasons, solar activity cycle phases, and interplanetary conditions. It has been found that most statistical distributions of magnetic impulse amplitudes have the exponent α larger than 2, which is typical of the chaotic regimes called “strong turbulence.” In some cases, the exponent α is close to 1, which is typical of the regimes generated in a weakly turbulent medium. Qualitative estimates of the plasma wave turbulence level in the high-latitude magnetosphere have been obtained.  相似文献   

20.
A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956–1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V × Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.  相似文献   

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