共查询到20条相似文献，搜索用时 31 毫秒
1.
Gu Zhen-Nian 《Earth, Moon, and Planets》1996,74(1):35-47
The earthquake produces a global static displacement field due to the dislocation in the epicenter. This displacement field in turn changes the Earth's inertia tensor, hence exciting the variation of both polar motion and length of day. In general, large earthquake produces greater displacement field, which has greater effects upon the earth rotational properties. In spite of scientists efforts in the last decades, it is found that the polar motion and the length of day excited by earthquake are at least two orders of magnitude less than those derived from observation. In the future with high observational accuracy the effect of earthquake on polar motion and length of day would be observable.Using the fault plane parameters, the location of epicenter and the expression given by Dahlen as well as the step function, the accumulative change of the axial and equatorial moments of inertia of the Earth earthquake occurring in period of 1977–1994 is estimated in this paper. Results have shown that change of pole axis direction induced by single earthquake is independent of the magnitude of the earthquake, which is random, but large earthquake contributes most to the accumulative change of direction of polar drift. The earthquake tends to make the drift of rotational pole towards the direction of 130–150 E. This direction is roughly different to that inferred from observations. Accumulative changes of both the two equatorial principal moments and the axial moment of inertia of the Earth present the strongest non-randomness and secular behaviour. The change depends upon the slip angle of the fault movement in a large extent. 相似文献
2.
M. Burša 《Earth, Moon, and Planets》1984,30(2):189-192
The discrepancy between the observed apparent acceleration of the Moon in longitude (1) and the actual lunar laser ranging data (3), (4) is of the order of ~ 9 × 10–23 rad s–2. It cannot be explained by the rms errors in (1) and (3), (4); processes connected with the internal Earth's dynamics and accelerating the Earth in its rotation might be responsible for the phenomenon, leading to the decreasing of the principal moment of the Earth's inertia ~ – 3.2 × 1029m2 kg cy–1. 相似文献
3.
Eleven microwave spike events observed with the 2.6–3.8 GHz spectrometer of Beijing Astronomical Observatory (BAO) are analysed. The polarization degrees of spikes are variable, some spikes have frequency drift with the drift rate of several GHz s–1. In particular, the time delay (8 ms) between the two polarization modes of spike is detected, which is different from previous results. According to the leading spot rule, we conclude that the o-modes arrive first. Moreover, the reversal of polarization sense versus frequency is also found. A change of the emission mode may be the cause of the polarization reversal. 相似文献
4.
The processes responsible for the emission of Na-D line in the Earth's atmosphere and laboratory are briefly reviewed. From the laboratory results of Ghoshet al. (1970), the rate coefficient of reactions exciting sodium D line is estimated to be 4.73×10–25 cm6/sec2, and its intensity in the nightglow is found to be about 114R in summer and 302R in winter. 相似文献
5.
V.N. Mel'nik A.A. Konovalenko H.O. Rucker A.A. Stanislavsky E.P. Abranin A. Lecacheux G. Mann A. Warmuth V.V. Zaitsev M.Y. Boudjada V.V. Dorovskii V.V. Zaharenko V.N. Lisachenko C. Rosolen 《Solar physics》2004,222(1):151-166
We present the results of radio telescope UTR-2 observations of solar Type II radio bursts in the 10–30 MHz frequency range. These events possess a fine structure consisting of fast drift sub-bursts similar to Type III bursts. The frequency drift rate of the Type II bursts at decameter wavelengths is smaller than 0.1 MHz s–1. One of these bursts with herringbone structure has a wave-like backbone that almost does not drift. The features of the observed bursts are discussed. 相似文献
6.
In this article, our previous Hamiltonian theory for the rotation of an Earth whose elastic mantle is deformed by rotation and linisolar attraction is applied to the study of the secular acceleration of the Earth's rotation. Since it is a result of the inelasticity, the theory is extended to include a phase lag. So, we obtain, in a theoretical way, a value of –5.6 × 10–22 rd sec–2, which agrees perfectly with the latest observational results. 相似文献
7.
Canceling magnetic features are commonly believed to result from magnetic reconnection in the low atmosphere. According to the Sweet–Parker type reconnection model, the rate of flux cancellation in a canceling magnetic feature is related to the converging speed of each pole. To test this prediction observationally, we have analyzed the time variation of two canceling magnetic features in detail using the high-resolution magnetograms taken by the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). As a result, we have obtained the rate and converging speed of flux cancellation in each feature: 1.3×1018 Mx hr–1 (or 1.1×106 G cm s–1 per unit contact length) and 0.35 km s–1 in the smaller one, and 3.5×1018 Mx hr–1 (1.2×106 G cm s–1) and 0.27 km s–1 in the bigger one. The observed speeds are found to be significantly bigger than the theoretically expected ones, but this discrepancy can be resolved if uncertainty factors such as low area filling factor of magnetic flux and low electric conductivity are taken into account. 相似文献
8.
We revise the published neutron monitor raw data for the increase caused by the solar neutron event of the 24 May 1990. With these data we calculate the attenuation length, , of solar neutrons in the Earth's atmosphere assuming either a minimum path as given by the spread of elastically scattered neutrons, or using the minimum mass path estimated by Smart, Shea, and O'Bren (1995) due to an atmospheric refraction effect. In both cases reduces to a value around 100 g cm–2, which is more in accordance with data on neutron cross-sections (Shibata, 1994). These two phenomenological calculations suggest that solar neutrons do not propagate in straight lines in the atmosphere. The previous estimate of the attenuation length, =208 g cm–2, was calculated assuming straight-ahead transport (Smart, Shea, and O'Bren, 1995). Dorman, Valdes-Galicia, and Dorman (1999) performed a numerical simulation and an analytical approximation to the problem of solar neutron scattering and attenuation in the Earth's atmosphere. These solutions incorporate the refraction effect as a natural consequence of the greater absorption experienced by neutrons scattered to large zenith angles. They are able to reproduce the normalised observed counting rates of neutron monitors for this event. 相似文献
9.
S. Latushko 《Solar physics》1993,146(2):401-404
The pattern of torsional oscillations was detected in the rotation of the large-scale magnetic field using the method of two-dimensional correlation functions. The position of areas of fast and slow rotation agrees with the Doppler picture obtained by Ulrich et al. (1988). The torsional wave amplitude is 20–40 ms–1 and increases with latitude. A strong correlation of the pattern of residual E-W rate with the meridional drift pattern, obtained from the same data, was determined. The sign of correlation is consistent with the results reported by Ward (1965). 相似文献
10.
B. A. Steves G. B. Valsecchi E. Perozzi A. E. Roy 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):341-358
The effect of changes in the Moon's semimajor axis and the Earth's orbital eccentricity on the occurrence of Saros-like cycles is examined. The Earth-Moon-Sun dynamical system exhibits such cycles for only 25 to 30% of the time interval between –5×107 to +5×107 years. Not only has the present Saros the smallest period during this time, but it also has one of the longest durations and the period closest to an integral number of anomalistic years, thus making it one of the most efficient Saros-like cycles for reversing solar perturbations in the main lunar problem. During the lifetime of a Saros-like cycle, variations of the Earth's orbital eccentricity cause frequent disappearances and reappearances of the cycle. 相似文献
11.
Numerical integration of particle trajectories is performed to evaluate the statistical acceleration coefficients D
TT for 1 to 100 MeV protons in a solar wind corotating interaction region (CIR) seen at 2.5 and 5.0 AU. Acceleration is followed in the solar wind reference frame and is due to random wave-particle interactions and to random drift motion in moderate scale field gradients. D
TT due to the first effect reaches a peak value of 4 × 10 –7 MeV2 s–1 post shock at 10 MeV at 2.5 AU consistent with estimates based both upon cyclotron resonance and transit time damping theory. D
TT from the second effect is less well established but is of the order of 10–7 MeV2 s–1 at 10 MeV, 5 AU. A comparison is made between the time constant for statistical acceleration within this CIR and estimates for diffuse shock acceleration and adiabatic deceleration. All three time constants are of the same order, but deceleration is faster than shock acceleration which in turn is faster than statistical acceleration. 相似文献
12.
We have previously studied large-scale motions using high-resolution magnetograms taken from 1978 to 1990 with the NSO Vacuum Telescope on Kitt Peak. Latitudinal and longitudinal motions were determined by a two-dimensional crosscorrelation analysis of pairs of consecutive daily observations using small magnetic features as tracers. Here we examine the shape and amplitude of the crosscorrelation functions. We find a characteristic length scale as indicated by the FWHM of the crosscorrelation functions of 16.6 ± 0.2 Mm. The length scale is constant within ±45° latitude and decreases by about 5% at 52.5° latitude; i.e., the characteristic size is almost latitude independent. The characteristic scale is within 3% of the average value during most times of the solar cycle, but it increases during cycle maximum at latitudes where active regions are present. For the time period 1978–1981 (solar cycle maximum), the length scale increases up to 1.7 Mm or 10% at 30° latitude. In addition, we derive the average amplitude of the crosscorrelation functions, which reflects the diffusion of magnetic elements and their evolutionary changes (including formation and decay). We find an average value of 0.091 ± 0.003 for the crosscorrelation amplitude at a time lag of one day, which we interpret as being caused by the combined effect of the lifetime of magnetic features and a diffusion process. Assuming a lifetime of one day, we find a value of 120 km2 s–1 for the diffusion constant, while a lifetime of two days leads to 230 km2 s–1.Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation. 相似文献
13.
S. Latushko 《Solar physics》1994,149(2):231-241
A method of two-dimensional correlation functions has been applied to a sequence of synoptic maps of the large-scale magnetic field to obtain the meridional drift pattern of field structures. The meridional drift profile obtained is antisymmetric about the equator. The meridional drift is directed from the equator to the poles at latitudes below 45°. A maximum drift velocity of 11–13 m s–1 is attained in the latitude range 30°. A picture of the space-time distribution of meridional drift is also obtained, which may be interpreted as resulting from the effect of azimuthal convective rolls (3 rolls per hemisphere) on the large-scale magnetic field. Rolls originate at high latitudes following the cycle maximum, and migrate equatorwards until the minimum of the next cycle. The picture in the equatorial region can correspond to convective rolls with lifetimes of about two years, or to the process of interaction of rolls from two hemispheres. 相似文献
14.
The average profile of Forbush decreases, produced by eastern-, central- and western-region solar flares is obtained separately by superposed epoch analysis for the periods 1966–1969 (qA < 0) and 1971–1979 (qA > 0). It is observed that the recovery of an average Forbush decrease from the maximum depression level is faster for the situation qA > 0 than for the situation qA < 0. This is in accordance with expectations from the drift theory. It is also observed that the drift effect is more pronounced for western-flare Forbush decreases which, of course, have a smaller magnitude compared to eastern- and central-flare Forbush decreases.The average profiles of simple and complex type Forbush decreases are also obtained separately for three periods 1965–1979, 1971–1979, and 1981–1987. It is found that the average profiles of simple and complex type Forbush decreases observed during the period 1965–1969 and 1971– 1979 are quite in agreement with drift theory. The anomalous behavior of average Forbush-decrease profiles during the period 1981–1987, especially in simple type Forbush decreases, is also explained by a drift current sheet tilt model. 相似文献
15.
Dimension of the Earth's General Ellipsoid 总被引：1，自引：0，他引：1
Burša Milan Kenyon Steve Kouba Jan Raděj Karel Šíma Zdislav Vatrt Viliam Vojtíšková Marie 《Earth, Moon, and Planets》2002,91(1):31-41
The problem of specifying the Earth's mean (general)ellipsoid is discussed. This problem has been greatly simplified in the era of satellite altimetry, especially thanks to the adopted geoidal geopotential value, W0 = (62 636 856.0 ± 0.5) m2 s-2.Consequently, the semimajor axis a of the Earth's mean ellipsoid can be easily derived. However, an a priori condition must be posed first. Two such a priori conditions have been examined, namely an ellipsoid with the corresponding geopotential that fits best W0 in the least squares sense and an ellipsoid that has the global geopotential average equal to W0. It has been demonstrated that both a priori conditions yield ellipsoids of the same dimension, with a–values that are practically identical to the value corresponding to the Pizzetti theory of the level ellipsoid: a = (6 378 136.68 ± 0.06) m. 相似文献
16.
R. K. Srivastava 《Astrophysics and Space Science》1987,132(2):331-335
The O–C diagram of the eclipsing binary GG Cassiopeiae has been presented for the first time, and the period changes present in the system have been analysed. In all three period changes are noted. The strongest period change has been found to occur in the time-interval 1942 to 1966. The total period change in different portions of the O–C diagram ranges from 7.1×10–7 d to 2.0×10–5 d. The stronger period changes appear to have occurred after 1942; prior to it, the system has shown a negligible period change. The overall picture of the O–C diagram suggests that the O–C values of the system GG Cas are negative after 1942. The presence of a third body does not appear probable. The period fluctuations are also appreciable. A new period (P=3
.
d
758733) has been presented. 相似文献
17.
In a previous paper Lyttleton (1976) has shown that the apparent secular accelerations of the Sun and Moon, as given by de Sitter, can be largely explained if the Earth is contracting at the rate required by the phase-change hypothesis for the nature of the core. More reliable values for these accelerations have since become available which warrant a redetermination of the various effects concerned on the basis of constantG, and this is first carried out in the present paper. The lunar tidal couple, which is the same whetherG is changing or not, is found to be (4.74±0.38)×1023 cgs, about three-quarters that yielded by the de Sitter values, while within the theory the Moon would take correspondingly longer to reach close proximity to the Earth at about 1.5×109 years ago.The more accurate values of the accelerations enable examination to be made of the effects that a decreasingG would have, and it is shown that a valueG/G=–3×10–11 yr–1 can be weakly satisfied compared with the close agreement found on the basis of constantG, while a value as large numerically asG/G=–6×10–11 yr–1 seems to be definitely ruled out. On the iron-core model, an intrinsic positive component of acceleration of the angular velocity cannot be reconciled at all with the secular accelerations even for constantG, and far less so ifG is decreasing at a rate suggested by any recent cosmological theory.ItG=0, the amount of contraction available for mountain-building would correspond to a reduction of surface area of about 49×106 km2 and a volume to be redistributed of 160×109 km3 if the time of collapse were 2.5×109 years ago. For earlier times, the values are only slightly reduced. IfG/G=–3×10–11 yr–1, the corresponding values are 44×106 km2 and 138×109 km3 for collapse at –2.5×109 yr, and not importantly smaller at 38×106 km2 and 122×109 km3 for collapse at –4.5×109 yr. Any of these values would suffice to account in order of magnitude for all the eras of mountain-building. An intense brief period of mountain-building on an immense scale would result from the Ramsey-collapse at whatever time past it may have occurred. 相似文献
18.
It is shown that a universal steady X-ray background with the energy flux 10–7 erg cm–2 s–1 sr–1 can arise as a superposition of radiation from pulsars (neutron stars) in various galaxies when it is taken into account that supernova outburst occurs in a galaxy at the rate of 10–2/year. 相似文献
19.
We study the evolution of an ensemble of energetic (1 GeV) protons in a twisted force-free magnetic loop. The protons are followed with a bounce-average method and they are subjected to collisions with ambient gas and pitch-angle scattering by plasrma turbulence in the loop. The proton loss is initially by drift and later by scattering into the loss cone. Gamma rays are produced by pion decays resulting from nuclear reactions of these lost protons. It is found that in order to have long-lasting protons, one of the following scenarios should hold: (1) For small loops (of length 2 × 109 cm), the twist angle should be about 2 and the turbulence level below 10–8 erg cm–3. (2) For large loops ( 1010 cm), the turbulence level should be below 10–6 erg cm–3. These set the conditions for testing the trapping picture as a viable explanation for the observed eight-hour gamma-ray emission. 相似文献
20.
R. K. Srivastava 《Astrophysics and Space Science》1987,129(1):143-147
A new period (P=3d.687664) of the eclipsing binary system IZ Persei is given, based on 16 observed times of the minima. O–C diagrams of IZ Per have been presented for the first time, and the period variations have been estimated in different portions of the O–C diagram. Significant period changes do not appear to have occurred in IZ Per. The O–C diagrams suggest that the period of the system is continuously increasing at a rate of 25s yr–1. Period variations of the order of 10–5 d appear to have occurred around the years 1969, 1972, and 1978. The period increases are stronger than the period decreases; but these are yet to be confirmed. The overall picture of IZ Per suggests that strong period changes are not present in the system; however, slow increase of period is apparent in IZ Per. The total period change (3×10–6 d) till the last epoch is in agreement with the newly derived period of IZ Per. 相似文献