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1.
Summary Solar and lunar geomagnetic tides inH at Alibag have been determined by spectral analysis of discrete Fourier transforms following the method of Black and the well-known Chapman-Miller method. The seasonal variation inL 2(H) is opposite to that inL 2(D) with maximum in thed season and minimum in thej season. In bothH andD the enhancement due to sunspot activity is larger in lunar tide than in solar tide. Surprisingly, the enhancement due to magnetic activity is greater inL 2(H) than inS 1(H), while the contrary is true for declination. It is inferred that there is a local time component of the storm time variation contrary to the view expressed by Green and Malin. The enhancements in amplitudesL 2 andS 1 inH andD, due to sunspot activity and due to magnetic activity, have been separated. The results show that the amplitude at zero sunspot number increases with magnetic activity in all the four parameters, while the enhancement due to sunspot activity at different levels of magnetic activity decreases with increase ofK p. But if bothK p andR are increasing, whenK p increases enhancement due toR decreases and whenR increases enhancement due toK p decreases.  相似文献   

2.
We have used time-delay feed-forward neural networks to compute the geomagnetic-activity index Dst one hour ahead from a temporal sequence of solar-wind data. The input data include solar-wind density n, velocity V and the southward component Bz of the interplanetary magnetic field. Dst is not included in the input data. The networks implement an explicit functional relationship between the solar wind and the geomagnetic disturbance, including both direct and time-delayed non-linear relations. In this study we especially consider the influence of varying the temporal size of the input-data sequence. The networks are trained on data covering 6600 h, and tested on data covering 2100 h. It is found that the initial and main phases of geomagnetic storms are well predicted, almost independent of the length of the input-data sequence. However, to predict the recovery phase, we have to use up to 20 h of solar-wind input data. The recovery phase is mainly governed by the ring-current loss processes, and is very much dependent on the ring-current history, and thus also the solar-wind history. With due consideration of the time history when optimizing the networks, we can reproduce 84% of the Dst variance.  相似文献   

3.
Geomagnetic solar and lunar daily variationsS andL, at Alibag, India are derived, by the well-known Chapman-Miller method, from the series of homogeneous mean hourly magnetic data of the years 1932 to 1972. The data for all the three elements — declinationD and horizontal and vertical intensitiesH andZ — are analysed, by dividing the data suitably for a study of the seasonal variations, the effect of the changes in the solar and magnetic activities onS andL, the oceanic dynamo contribution toL, and their interactions with each other. The main results are as follows.
  1. ForS the daily pattern and its seasonal progression conform to the type expected from a northern-hemisphere station. On the other hand, the amplitudes of all the four harmonics ofL systematically have higher values in winter, and inD andZ the harmonics show large phase differences between summer and winter. The pattern ofL in winter suggests that the lunar current system consists of a single set of vortices in the summer hemisphere rather than the conventional vortices, one set in each of the hemispheres.
  2. Solar-cycle modulation on the solar ranges as well as on the amplitudes of the first three harmonics ofS is greater than that expected solely from the increase in E-region conductivity, whereas the corresponding modulation onL is comparable to that on the E-region conductivity.
  3. With increasing magnetic activity the first harmonic ofS shows an increase, and the first three harmonics ofL indicate a general decrease, in amplitude.
  4. Of the variability inS 96%, but inL only 32%, is found to be accounted for by the combined effect of the variations in the solar and magnetic activities.
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4.
Summary Measuring, with the aid of two filters, the instantaneous intensity of the solar radiation in two wave lengths ( B = 0.44 , R = 0.64 ) by means of a sun photometer designed byVolz, we carried out determinations of the decadic turbidity coefficientB (=0.5 ) and the wave length exponent of the haze extinction for Mexico City. Observations were made for almost two and a half years (1960 to 1962 period). A seasonal size distribution in both parameters was found. Although the data thus obtained are provenient of a contaminated atmosphere, comparison of our data is made with those found for higher latitudes ofÅngström, Schüepp andVolz. The height of the homogeneous haze layerH D was calculated showing pronounced variations for a given wind direction. The maximum and minimum values ofB enable us to get, by the first approximation, the aerosol size distribution ofJunge for our latitudes. However, for exceptional very clear days having maximum actinometric intensity of the solar radiation the sensitivity of the microamperimeter in theVolz sun photometer fails.  相似文献   

5.
This review deals with how the changes of the large-scale solar magnetic fields are related to the occurrence of solar phenomena, which are associated with geomagnetic storms. The review also describes how artificial neural networks have been used to forecast geomagnetic storms either from daily solar input data or from hourly solar wind data. With solar data as input predictions 1–3 days or a month in advance are possible, while using solar wind data as input predictions about an hour in advance are possible. The predictions one hour ahead of the geomagnetic storm indexD st from only solar wind input data have reached such high accuracy, that they are of practical use in combination with real-time solar wind observations at L1. However, the predictions days and a month ahead need to be much improved in order to be of real practical use.  相似文献   

6.
Summary The lunar daily (L) and lunar monthly (M) variations in horizontal magnetic field (H), maximum electron density (N max ), height of peak ionisation (h max ), semi-thickness (y m ) of theF 2 layer and total electron content (N t ) at Huancayo for the period January 1960 to December 1961 are described. The lunar tidal variations inh max follow sympathetically the variations inH such that an increase of magnetic field causes the raising of height of peak ionisation. Lunar tides inN max are opposite in phase to that ofh max with a delay of about 1–2 hours, suggesting that an increase of height causes a decrease in maximum electron density. The lunar tides in semi-thickness are very similar in phase to that inh max . The lunar tidal effects in any of the parameters are largest inD-months and least inJ-months. The amplitude of lunar tides in maximum electron density seems to increase with increasing height whereas the phase seems to be constant with height. It is concluded that lunar tides in the ionospheric parameters at magnetic equator are greatly controlled by the corresponding geomagnetic variations.Presented at the Third International Symposium on Equatorial Aeronomy, Ahmedabad, 3–10 February 1969.  相似文献   

7.
A layeredP- andS-wave velocity model is obtained for the Friuli seismic area using the arrival time data ofP- andS-waves from local earthquakes. A damped least-squares method is applied in the inversion.The data used are 994P-wave arrival times for 177 events which have epicenters in the region covered by the Friuli seismic network operated by Osservatorio Geofisico sperimentale (OGS) di Trieste, which are jointly inverted for the earthquake hypocenters andP-wave velocity model. TheS-wave velocity model is estimated on the basis of 978S-wave arrival times and the hypocenters obtained from theP-wave arrival time inversion. We also applied an approach thatP- andS-wave arrival time data are jointly used in the inversion (Roecker, 1982). The results show thatS-wave velocity structures obtained from the two methods are quite consistent, butP-wave velocity structures have obvious differences. This is apparent becauseP-waves are more sensitive to the hypocentral location thanS-waves, and the reading errors ofS-wave arrival times, which are much larger than those ofP-waves, bring large location errors in the joint inversion ofP- andS-wave arrival time. The synthetic data tests indicated that when the reading errors ofS-wave arrivals are larger than four times that ofP-wave arrivals, the method proposed in this paper seems more valid thanP- andS-wave data joint inversion. Most of the relocated events occurred in the depth range between 7 and 11 km, just above the biggest jump in velocity. This jump might be related to the detachment line hypothesized byCarulli et al. (1982). From the invertedP- andS-wave velocities, we obtain an average value 1.82 forV p /V s in the first 16 km depth.  相似文献   

8.
The hourly averaged Polar Cap (PC) index was used as the input parameter for the ring current index Dst variation forecasting. The PC index is known to describe well the principal features of the interplanetary magnetic field as well as the total energy input to the magnetosphere. This allowed us to design a neural network that was able to forecast the Dst variations 1 h ahead. 1995 PC and Dst data sets were used for training and testing and 1997 data sets were used for validation. From 15 moderate and strong geomagnetic storms observed during 1997, 10 were successfully forecasted. In 3 cases the observed minimum Dst value was less than the predicted value, and only in 3 cases the neural network was not able to reproduce the features of the geomagnetic storm.  相似文献   

9.
Summary A modified method of computing theS q -range in terms ofR x inH, D andZ has been suggested. Mean quiet-day daily rangesR x , have been computed for five Indian stations usingH, D andZ data for selected years. The seasonal and latitudinal variation ofR x (H), R x (Z) andR x (D) are discusses. Thee-season maximum inR x (H) andR x (Z) is attributed to the decrease in the distance between the foci during equinoxes; the electrojet and theS q -foci movement with seasons have little influence onS q (D). It is inferred that the electrojet current is independent of the worldwideS q current system and stands with its own return currents.The variation of lunar semi-diurnal tide inH[L 2 (H)] with the dip latitude in Indian region shows a secondary peak at 9° N dip latitude. This secondary peak in theL 2 (H) is termed as Lunar secondary electrojet, and it is suggested that this is possibly produced by magneto-acoustic oscillations due to the drift motion of the charged particles that produce the primary jet in a direct transverse to itself.  相似文献   

10.
Global GPS-derived ionosphere maps (GIM) of total electron content (TEC) were transformed into magnetic latitude (MLAT) versus magnetic local time (MLT) frame. TEC enhancement or depletion marked by W index show dominant electron content depressions and the ionosphere–plasmasphere storms increasing by nighttime, at high magnetic latitudes and over the crests of equatorial anomaly. Based on W maps, the planetary Wp index was produced and used for derivation of a catalogue of more than 140 TEC storms during 1999–2009. In total 33 space weather intense storms and 35 moderate storms are revealed with four series of indices (AE, Ap, Dst and Wp) but more than half Wp storms were either partially overlapping in time with magnetic storm or observed autonomously under non-storm magnetosphere conditions. Relation between an annual number of intense Dst storms and Wp storms has been used for their prediction towards the peak of the forthcoming 24th solar cycle.  相似文献   

11.
The main causes of the main phases of geomagnetospheric storms (D st min = ?(37?226) nT) have been studied using a cluster analysis in the form of the nearest neighbor method. Weak, moderate, strong and severe storms (samples) related to the IMF B Z component have been distinguished based on the two-dimensional (with respect to the IMF B Z component and D st index) scale cluster classification of storm main phases. The correlation clustering of 32 interrelated physical processes characterizing each main phase made it possible to determine that interrelated physical processes included the common part of the internal structure for all samples. The studied samples of storm main phases are characterized by different physical development levels, depending on the event scale. The presence of a common part indicates that magnetospheric activity mostly depends on the IMF B Z and B Y components and the coupling functions between them, as well as on the total IMF B value during the main phases of storms of all D st index scales. It has been established that the closest relationships are typical of D st (V 2 B S ) and D st (VB S ), where B S is the IMF southward component, and V is the solar wind velocity. Substorm activity (AE) generated by V 2 B S and VB S is only substantial during the main phases of weak and moderate storms, whereas grouping with respect to the velocity V only shows substantial activity during severe magnetic storms. The role of the Akasofu parameter (?) proved to be less pronounced. It has been indicated that, in a first approximation, it is preferred to use the V 2 B S and VB S coupling functions in order to predict the D st index and estimate the injection function Q during the main phases of geomagnetospheric storms.  相似文献   

12.
Summary The discrepancy between the observed values off 0 E and those computed on the basis of theChapman theory was examined. Taking monthly mean values of stations in various latitudes for the year 1958 it was shown, that the diurnal variation of indexn changes in higher latitudes becoming similar to that in the neighbourhood of the equator. This phenomenon may be attributed to the effect of a vertical drift produced by an overhead current system in that part of the dayside ionosphere. Further it was shown, that the variation of indexn with increasing solar activity is largely due to the increase of the recombination coefficient and that of the scale height.  相似文献   

13.
The paper studies the effect of magnitude errors on heterogeneous catalogs, by applying the apparent magnitude theory (seeTinti andMulargia, 1985a), which proves to be the most natural and rigorous approach to the problem. Heterogeneities in seismic catalogs are due to a number of various sources and affect both instrumental as well as noninstrumental earthquake compilations.The most frequent basis of heterogeneity is certainly that the recent instrumental records are to be combined with the historic and prehistoric event listings to secure a time coverage, considerably longer than the recurrence time of the major earthquakes. Therefore the case which attracts the greatest attention in the present analysis is that of a catalog consisting of a subset of higher quality data, generallyS 1, spanning the interval T 1 (the instrumental catalog), and of a second subset of more uncertain magnitude determination, generallyS 2, covering a vastly longer interval T 2 (the historic and/or the geologic catalog). The magnitude threshold of the subcatalogS 1 is supposedly smaller than that ofS 2, which, as we will see, is one of the major causes of discrepancy between the apparent magnitude and the true magnitude distributions. We will further suppose that true magnitude occurrences conform to theGutenberg-Richter (GR) law, because the assumption simplified the analysis without reducing the relevancy of our findings.The main results are: 1) the apparent occurrence rate exceeds the true occurrence rate from a certain magnitude onward, saym GR; 2) the apparent occurrence rate shows two distinct GR regimes separated by an intermediate transition region. The offset between the two regimes is the essential outcome ofS 1 being heterogeneous with respect toS 2. The most important consequences of this study are that: 1) it provides a basis to infer the parameters of the true magnitude distribution, by correcting the bias deriving from heterogeneous magnitude errors; 2) it demonstrates that the double GR decay, that several authors have taken as the incontestable proof of the failure of the GR law and of the experimental evidence of the characteristic earthquake theory, is instead perfectly consistent with a GR-type seismicity.  相似文献   

14.
Summary The article describes lunar daily magnetic variation inH, D andZ components of the earth's magnetic field at Istanbul. Maximum occurs at 10.03 l.hr. (lunar hour) in theH component, 3.38 l.hr. in theD and 2.15 l.hr. in theZ component, during the period 1949 to 1968. Also, the seasonal variation of the lunar magnetic variation has been determined and it is seen that the variation of the phase inD andZ are opposite from the phase of the lunar variation inH, and the amplitudes of the lunar variation inH, D andZ are greatest during the northern solstice.  相似文献   

15.
In a large coil with vertical axis the current is adjusted so thatZ=0. A smaller coil of a new type with four sets of cylindrical turns is placed with its axis horizontal. ThisD-coil is provided with a telescope pointing at a mark nearly in the magnetic meridian. A proton magnetometer sensor is placed in the common centre of the coils. Two series of readings are taken with theD-coil in the erect and inverted position respectively. Variations ofD, H, F, andD-coil current are recorded. A simple formula gives the mean value ofD.  相似文献   

16.
A review of modern dynamic models of the Earth’s magnetosphere (the A2000 paraboloid model and Tsyganenko’s T01 model) is presented. For the magnetic storm of January 9–11, 1997, the results of joint calculations of the magnetospheric magnetic field are presented and contributions of the large-scale magnetospheric currents to the D st variations are analyzed. Both models were shown to be well consistent with measurement data; the contribution of the magnetotail current system to D st is comparable to the contribution of the ring current. At the same time, the relative dynamics of magnetospheric current systems are different in different models. The differences in the magnetic field variation profiles for various current systems calculated by the A2000 and T01 models are explained by model parameterizations.  相似文献   

17.
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   

18.
Cataclasis and processes of particle size reduction   总被引：6，自引：0，他引：6  
The particle size distribution (P.S.D.) of fragmented geological materials is affected by the fragmentation process, initial size distribution, number of fracturing events, energy input, strain, and confining pressure. A summary of literature shows that the fractal dimension (D) of the P.S.D. is increased by the number of fracturing events, energy input, strain, and confining pressure. Cenozoic cataclasis of granite, granodiorites, gneisses and arkose seen in cores from the Cajon Pass drillhole, southern California, produced P.S.D.s with values ofD that varied from 1.88 to 3.08. Each rock type has a characteristic and more limited range ofD. Areas of dilatant texture and modeI fracture-fillings have low average values (2.32 and 2.37) compared to an average value of 2.67 in shear fracture-fillingsD has a good inverse correlation with average particle size. Data from fault rocks in the San Gabriel fault zone, southern California (Anderson et al., 1983) have been reanalyzed to show that values ofD are higher (2.10–5.52) and average particle size is lower than the Cajon Pass samples, but the ranges of values overlap, and the inverse correlation betweenD and average particle size is extended. Microstructural observations combined with these results suggest that three processes contributed to particle size reduction during cataclasis. The first process of feldspar alteration, which leads to low values ofD, has not been previously recognized. The second process is probably constrained comminution (Sammis et al., 1987), since the averageD in shear fracture-fillings is close to the value of 2.58 predicted by this theory. A further stage of particle size reduction is demonstrated by an increase ofD with cataclasis. This third process is selective fracture of larger particles, which may also operate during localization and the cataclastic flow-to-faulting transition as observed in experiments. A transition from constrained comminution to selective fracture of large particles, and increasingD values with cataclastic evolution and grain size reduction, may be general features of experimental and natural cataclasis.  相似文献   

19.
Lunar and solar atmospheric tidal oscillations have been determined with reasonable accuracy from a ten-year record of hourly mercury-barometer readings, corrected to mean-sea-level, at Rarotonga (Cook Islands), 21.2°S. For the lunar semidiurnal tide, the annual determination shows an amplitude (56 b) slightly lower and a phase (51°) much smaller than the values (58 b, 72°) that would be derived, for the position of Rarotonga, from the spherical harmonic analysis given byHaurwitz andCowley (1969). The seasonal variation of this oscillation, as given by the monthly and J, E, D values, shows most of the characteristic features found in world-wide determinations. In particular, the near equality of the J, D amplitudes at Rarotonga tends to support theHaurwitz andCowley (1969) suggestion of negative J-D values in southern middle latitudes. For the solar tides, the semidiurnal and terdiurnal oscillations at Rarotonga are similar to those found at other stations in the south-west Pacific region. However, for the diurnal oscillation, the annual amplitude (232 b) is only about half the value (465 b) indicated for the position of Rarotonga by the world maps of theS 1(p) annual harmonic coefficients given byHaurwitz (1965). It thus seems likely that the relatively small area of lowS 1(p) annual amplitude in the eastern part of the south Pacific, as indicated by these maps, is much more extensive than formerly supposed.  相似文献   

20.
Summary Regional variations have been indicated in the slope of theP travel-time curve in the shadow zone of the earth's core. Further study is needed since the uncertainties of the slope are large, especially for the observations from North American stations. There is no significant difference between themean slope of theP travel-time curve in the 95°102.9 range and those obtained byJeffreys, andJeffreys andBullen. However, there is a significant difference between themean slope in the 103° to 135° range as obtained in this study, and those obtained byJeffreys andBullen, and in a later revision byJeffreys. Themean travel-time curve ofP in the shadow zone of the earth's core should be lowered. A trial travel-time table is given with amean slope of 4.41 sec/deg. This table is in close agreement with the times obtained byGutenberg andRichter, and with the trial travel-times ofLehmann. Under the assumption of diffraction the longitudinal wave velocity has been determined to be 13.7 km/sec at the core-mantle boundary.This paper was presented at the Annual Meeting of the Seismological Society of America Reno, Nevada, 1966.  相似文献   

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