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1.
Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H) is associated with a simultaneous increase of eastward geomagnetic field (Y). It is shown that during the counter electrojet period when H is negative, Y also becomes negative. Thus, the diurnal variation of Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej). At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej), a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.  相似文献   

2.
Summary The derivatives of the harmonicsP n (k) (sin O)cos kTO andP n (k) (sin O)sin kTO, occurring in the development of the lunar disturbing potential, are derived upto n=4 and for k== 0, 1, ..., n. The equatorial co-ordinates OTO are referred to the Moon's mass centre; the procedure for the solar disturbing potential is formally identical.  相似文献   

3.
Summary The problem of the propagation of finite Love Waves in a heterogeneous elastic half space lying over a homogeneous elastic half space, using the quasilinear stress-strain relation due toS. Ferhst [4] is considered in detail. The variations of the parameter in the layer assumed to be of the form 1= 0e z, 0e z where is a constant andz is distance measured from the surface into the layer.  相似文献   

4.
Résumé Les observations des variations luni-solaires de la gravité en divers points du globe ne donnent pas des valuers très concordantes pour le facteur lié au module de rigidité de la Terre. On démontre ici que la répartition croissante des densités vers le centre de la Terre a pour conséquence d'amplifier encore les effets dus à l'élasticité. En adoptant la répartition deBullen, on aurait =1+0.244h>1, (h étant le premier nombre deLove). En outre une relation simple lie les facteurs et (déviations de la verticale). La valuer deh déduite de telles observations ne peut conduire directement à une valeur significative du module de rigidité du globe car il faut encore tenir compte des variations de la période et de l'amplitude du mouvement chandlérien du pôle.
Summary Observations of luni-solar variations of gravity at various points of the Earth do not give values in agreement for the factor bound to the Earth's modulus of rigidity. It is shown here that the law of increasing of density toward the center of the Earth emphasizes the effect of elasticity: following the law ofBullen, we should have =1+0.244h>1, (h is the firstLove's number). Further, there is a simple relation between the factors and (deviations of the vertical). The value ofh deduced from such observations could not give directly a significative value of the modulus of rigidity because we must take into account the variations of period and amplitude of the chandlerian motion of the pole.
Riassunto Le osservazioni delle variazioni luni-solari della gravità in diversi punti della Terra non dànno valori concordanti per il fattore legato al modulo di rigidità del Globo. Si dimostra che la ripartizione crescente della densità verso il centro della Terra ha per conseguenza di amplificare ancora gli effetti dell'elasticità; adottando la legge diBullen, abbiamo =1+0.244h>1, (h essendo il primo numero diLove). Inoltre, una semplice relazione lega i fattori e (deviazioni della verticale). Il valore dih dedotto da tali osservazioni non può condurre ad un valore significativo del modulo di rigidità del Globo poiché bisogna considerare anche le variazioni del periodo e dell'ampiezza del moto polare diChandler.
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5.
A general formula for the Dieterich-Ruina friction constitutive law with rate and state (n-state variables,n=1, 2,...) dependences has been obtained and discussed under the assumption that the slip acceleration a varies ion a linearly with the slip displacement , namelya = a 0 + (-0). Wherea 0, 0 are initial constants, is the acceleration rate and constant.a 0 and may be arbitrary constants (positive, negative or zero).The extreme value of frictional resistance and the existence condition of the extreme value, which are very important and govern to some degree the motion process of a frictionally slipping mechanical system, have been analyzed. A critical value c which is the measure of the velocity weakening and velocity strengthening of the mechanical system, and its properties and the relationship to the extreme problem have been studied. Again, according to the critical value c, the concepts of light or strong velocity weakening (or strengthening) are introduced.A possibly new phenomenon that frictional resistance may vary in some kind of decayed oscillation is found. Finally, the condition for the smallest frictional resistance for a slipping mechanical system with nonuniform acceleration has been obtained.  相似文献   

6.
The typical quiet day variations of the equatorial electrojet (EEJ) current intensity with time of the day, season, sunspot number, and geomagnetic latitude are presented in terms of the corresponding variations of H which is the deviation of the horizontal component (H) of the geomagnetic field from its steady nighttime level. The observed height structure of the current density in the EEJ as measured in rocket flights is presented, along with the theoretically computed structure. Theoretical model results on the polarization electric fields and east-west currents as generated by the local interactions of height-varying winds in the EEJ show large height gradients and reversals for both currents and electric fields; experimental evidence for the reality of such height structures is also shown. The characteristics of the counter-electrojet events are presented and the possible causative mechanisms are discussed critically.Some typical experimental results are presented on the electric field changes in the EEJ which result from its sensitive response to electrodynamic disturbances in the magnetosphere and the auroral-polar latitude ionosphere during geomagnetic substorms and storms; and their implications are discussed. Possibilities for utilizing the EEJ as a very useful medium for important scientific studies on the larger space domain of ionosphere-magnetosphere system, on plasma waves, and on the earth's conductivity are emphasized.  相似文献   

7.
Superposed epoch studies have been carried out in order to determine the ionospheric response at mid-latitudes to southward turnings of the interplanetary magnetic field (IMF). This is compared with the geomagnetic response, as seen in the indices Kp, AE and Dst. The solar wind, IMF and geomagnetic data used were hourly averages from the years 1967–1989 and thus cover a full 22-year cycle in the solar magnetic field. These data were divided into subsets, determined by the magnitudes of the southward turnings and the concomitant increase in solar wind pressure. The superposed epoch studies were carried out using the time of the southward turning as time zero. The response of the mid-latitude ionosphere is studied by looking at the F-layer critical frequencies, foF2, from hourly soundings by the Slough ionosonde and their deviation from the monthly median values, foF2. For the southward turnings with a change in Bz of Bz > 11.5 nT accompanied by a solar wind dynamic pressure P exceeding 5 nPa, the F region critical frequency, foF2, shows a marked decrease, reaching a minimum value about 20 h after the southward turning. This recovers to pre-event values over the subsequent 24 h, on average. The Dst index shows the classic storm-time decrease to about –60 nT. Four days later, the index has still to fully recover and is at about –25 nT. Both the Kp and AE indices show rises before the southward turnings, when the IMF is strongly northward but the solar wind dynamic pressure is enhanced. The average AE index does register a clear isolated pulse (averaging 650 nT for 2 h, compared with a background peak level of near 450 nT at these times) showing enhanced energy deposition at high latitudes in substorms but, like Kp, remains somewhat enhanced for several days, even after the average IMF has returned to zero after 1 day. This AE background decays away over several days as the Dst index recovers, indicating that there is some contamination of the currents observed at the AE stations by the continuing enhanced equatorial ring current. For data averaged over all seasons, the critical frequencies are depressed at Slough by 1.3 MHz, which is close to the lower decile of the overall distribution of foFl values. Taking 30-day periods around summer and winter solstice, the largest depression is 1.6 and 1.2 MHz, respectively. This seasonal dependence is confirmed by a similar study for a Southern Hemisphere station, Argentine Island, giving peak depressions of 1.8 MHz and 0.5 MHz for summer and winter. For the subset of turnings where Bz > 11.5 nT and P 5 nPa, the response of the geomagnetic indices is similar but smaller, while the change in foF2 has all but disappeared. This confirms that the energy deposited at high latitudes, which leads to the geomagnetic and ionospheric disturbances following a southward turning of the IMF, increases with the energy density (dynamic pressure) of the solar wind flow. The magnitude of all responses are shown to depend on Bz. At Slough, the peak depression always occurs when Slough rotates into the noon sector. The largest ionospheric response is for southward turnings seen between 15–21 UT.  相似文献   

8.
Using the hourly mean data of the horizontal (H) and vertical (Z) components of the geomagnetic field at the set of nine observatories in India, it has been found that the Disturbance Daily Variation (SD) of H shows a prominent midday depression over the magnetic equator of the H field and a midday increase of Z field at stations near the northern fringe of the equatorial electrojet belt. The magnetic disturbance introduces a westward electric field over the equatorial region, causing a band of westward ionospheric current over the magnetic equator during the day time hours. The latitudinal extent of the disturbance time counter electrojet current seems to be larger than that of quiet time normal electrojet current. This suggests a systematic westward electric field superposed on the normal Sq field at low latitude ionosphere during disturbed periods, the source of which has to be clearly defined. Further correlative data analysis is required to isolate these sources of the disturbed equatorial electric fields.  相似文献   

9.
Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400–0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800–0950 UT. Subsequent to the change in hF during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The H variations observed at the equator are the sum of the following components: SR, DP, DR, DCF and DT.  相似文献   

10.
Previous magnetic and geochemical studies of stream sediments in the Northeast of Buenos Aires Province, in the Greater La Plata area, have revealed a high level of trace elements, especially lead and zinc. Continuing these preliminary works, new sampling sites were considered in order to improve and increase the magnetic mapping of this area. This part of the study focuses especially on the magnetic properties of sediments from a cross-city stream. Such stream receives a variable pollutant load from urban, industrial and diffuse sources.Concentration-dependent magnetic parameters, magnetic carriers (para, anti and ferrimagnetic) and their features (e.g. softer or harder magnetic carrier, grain size distribution, etc.) have been calculated using magnetic measurements. According to magnetic parameters and heavy metal loads two main distinctive groups of sediment-cores are distinguished. The vertical distribution of sediments reveals a recent anthropogenic influence, possibly, belonging to the last 20-40 years.Four out of all the magnetic parameters (magnetic susceptibility, anhysteric remanent magnetisation, S-ratio and ARM/) were chosen in order to investigate their relationship with contents of heavy metals. In all the cases, good positive correlations were obtained using linear regression. However, more significant correlation factors were achieved for grain size and magnetic feature-dependent parameters ( ARM/ and S-ratio) than for magnetic concentration-dependent parameters. Therefore, the ARM/ and the S-ratio seem to be the most relevant magnetic parameters to describe the vertical and longitudinal distribution of heavy metals present in these stream sediments. The non-significant relationship between heavy metals and concentration-dependent parameters could be explained taking into account the discrimination of the two distinctive groups. The group belonging to the Coastal Plain shows a clear linear trend between heavy metals and magnetic susceptibility and anhysteric remanent magnetisation.  相似文献   

11.
A detailed analysis of the responses of the equatorial ionosphere to a large number of severe magnetic storms shows the rapid and remarkable collapse of F-region ionisation during post-midnight hours; this is at variance with the presently accepted general behaviour of the low-latitude ionosphere during magnetic storms. This paper discusses such responses as seen in the ionosonde data at Kodaikanal (Geomagn. Lat. 0.6 N). It is also observed that during magnetic storm periods the usual increase seen in the hF at Kodaikanal during sunset hours is considerably suppressed and these periods are also characterised by increased foF2 values. It is suggested that the primary process responsible for these dramatic pre- and post-midnight changes in foF2 during magnetic storms could be due to changes in the magnitude as well as in the direction of usual equatorial electric fields. During the post-midnight periods the change in electric-field direction from westward to eastward for a short period causes an upward E × B plasma drift resulting in increased hF and decreased electron densities in the equatorial region. In addition, it is also suggested that the enhanced storminduced meridional winds in the thermosphere, from the poles towards the equator, may also cause the decreases in electron density seen during post-midnight hours by spatially transporting the F-region ionisation southwards away from Kodaikanal. The paper also includes a discussion on the effects of such decreases in ionisation on low-latitude HF communications.  相似文献   

12.
Summary The paper deals with a comparison of two models used in determining the heat flow qM at the lower boundary of two-dimensional geothermal models of the Earth's crust. Method I is based on a linear relationship between the component of the surface heat flow, which is not generated by heat sources inside the model, and the heat flow qM. This method uses a regularization process, in which the variation of the sought function qM is limited from above. Method II is the most frequently used iterative method, in which the (i + 1)-th approximation of qM is determined from the surface heat flow, corresponding to the i-th approximation of qM used as a boundary condition in solving the direct problem. The comparison of both methods has revealed that the solution obtained by method I satisfies the supposed reality better than the solution obtained by method II. Method II is attractive especially for its simplicity. To eliminate the local variations of the estimated heat flow qM, which are due to automatic transmission from the surface heat flow, a combination of method II with some smoothing procedure could be applied.
¶rt;am ¶rt;a m¶rt;a uu mn nma qM a uau ¶rt; muu ¶rt; . m¶rt; unm u ¶rt; ma nm nma, ma uaa umuau mna mu ¶rt;u, u nm qM. m m¶rt; nu n uauu, auuau auau u uu qM . m m¶rt;, mu nm ¶rt; u n a , umau: (i + 1)-a annuau nma qM um n auma nm nma, ma i- annuauu qM. au ¶rt;m, m nm qM, a¶rt; n m¶rt;, mam n¶rt;naa ¶rt;mummu , u, n m m¶rt;. m m¶rt; nuam nmm. ¶rt; mau a auau a¶rt; nma qM, uu ¶rt;mu amamu na u auau nm nma, ¶rt;a uuam au-u¶rt; m¶rt; auau.
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13.
This work reviews some aspects of the ionospheric F-layer in the vicinity of the geomagnetic equator. Starting with a historical introduction, brief summaries are given of the physics that makes the equatorial ionosphere so interesting, concentrating on the large-scale structure rather than the smaller-scale instability phenomena. Several individual topics are then discussed, including eclipse effects, the asymmetries of the equatorial trough, variations with longitude, the semiannual variation, the effects of the global thermospheric circulation, and finally the equatorial neutral thermosphere, including superrotation and possible topographic influences.  相似文献   

14.
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15.
Summary On the basis of investigating 10 storms (1965–1967) good correlation was found between the density of the solar wind energy (2=1/2mNv2) and the intensity of the main phase of the geomagnetic storms, expressed in terms of the maximum decrease of the horizontal intensity (B=H/cos). The relation between 2, or Nv2, and B could then be used to determine the quantities and 0 ( is the factor expressing the increase in energy density in the magnetosphere, 0 is the energy density of the particles in a quiet magnetosphere). A comparison with the directly observed distribution of the energy density of the particles in the magnetosphere indicates that the computed value of 0 seems to be realistic. The magnitude of the factor will have to be checked again.  相似文献   

16.
Summary In this paper the generalized thermoelastic longitudinal waves and the temperature field set up due to coupling of the displacement and the temperature fields, with heat wave travelling with certain finite velocity, in an unbounded medium are studied. The thermoelastic displacement potential and the temperature field at any point are obtained in terms of the surface integrals involving the potential, the temperature and their normal derivatives.Notation x i the cartesian coordinate system,i=1,2,3 - n (u i) the displacement vector - (/x i) the del operator - t /t the derivative with respect to time - T o the temperature corresponding to the natural stat of zero stress and strain - T Absolute temperature - c e the specific heat - , Lamé's constants - 0 the density - coefficient of linear thermal expansion - K thermal conductivity coefficient - kk u - 0 the relaxation time  相似文献   

17.
TeleseismicP-waves of some large earthquakes that occurred in the eastern Mediterranean region have been analysed by using an iterative maximum entropy technique in order to obtain the independent spectral parameters, the long-period spectral level 0 and the corner frequencyf 0 of the far-field displacement spectra.Based on these parameters, the seismic source parameters seismic momentM 0, source dimensionr, fault lengthl, average displacement u, shear stress drop , radiated energyE s and apparent stressn are calculated for the considered earthquakes by using Brune's and Madariaga's models.The striking feature of the source parameters obtained in this study is the low stress drop value which varies between 5 and 15 bars. If Madariaga's model had been used, higher stress drop values would have been obtained.The low stress drop earthquakes in the eastern Mediterranean region might be interpreted either by the possible presence of low strength material near the source or by the partial stress drop model.  相似文献   

18.
The dawn and dusk electrojet response to substorm onset   总被引：1，自引：0，他引：1  
We have investigated the time delay between substorm onset and related reactions in the dawn and dusk ionospheric electrojets, clearly separated from the nightside located substorm current wedge by several hours in MLT. We looked for substorm onsets occurring over Greenland, where the onset was identified by a LANL satellite and DMI magnetometers located on Greenland. With this setup the MARIA magnetometer network was located at dusk, monitoring the eastward electrojet, and the IMAGE chain at dawn, for the westward jet. In the first few minutes following substorm onset, sudden enhancements of the electrojets were identified by looking for rapid changes in magnetograms. These results show that the speed of information transfer between the region of onset and the dawn and dusk ionosphere is very high. A number of events where the reaction seemed to preceed the onset were explained by either unfavorable instrument locations, preventing proper onset timing, or by the inner magnetospheres reaction to the Earthward fast flows from the near-Earth neutral line model. Case studies with ionospheric coherent (SuperDARN) and incoherent (EISCAT) radars have been performed to see whether a convection-induced electric field or enhanced conductivity is the main agent for the reactions in the electrojets. The results indicate an imposed electric field enhancement.  相似文献   

19.
Summary The theory of determination of figures of synchronously orbiting satellites is presented based on equipotential level ellipsoids representing the given external equipotential surfaces. The theory has been applied to seven synchronously orbiting satellites in the solar System. The numerical values of the polar and equatorial flattenings of the level ellipsoids suggest the conclusion that tidal and rotational distortions are responsible for the actual figures of the seven synchronously orbiting satellites.Dedicated to the Memory of Professor Karel P  相似文献   

20.
To obtain the temperatureT and volumeV (or pressureP) dependence of the Anderson-Grüneisen parameter T , measurements with high sensitivity are required. We show two examples:P, V, T measurements of NaCl done with the piston cylinder and elasticity measurements of MgO using a resonance method. In both cases, the sensitivity of the measurements leads to results that provide information about T (,T), where V/V 0 andV 0 is the volume at zero pressure. We demonstrate that determination of T leads to understanding of the volume and temperature dependence ofq=( ln / lnV) T over a broadV, T range, where is the Grüneisen ratio.  相似文献   

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