Lunar daily distance numbersD andD′     

Jagdish Chandra Gupta 《Earth, Moon, and Planets》1975,14(2):247-253

In analyses of the effect of variation of the Earth-Moon distance on geophysical phenomena, it is customary to arrange the geophysical data according to the dates of apogee and perigee. However, lunar distances at apogee and especially at perigee vary within wide limits from month to month. A new daily indexD' of lunar distance is defined to permit a more precise determination of effects related to lunar distance. It is readily calculated by a computer program.  相似文献   

Some studies on the solar microwave bursts in relation to the slowly varying component     

M. K. Das Gupta  S. K. Sarkar 《Solar physics》1972,26(2):378-385

The occurrences of 5772 microwave bursts recorded by the Sagamore Hill and Manilla Solar Radio Observatories over the period January 1968 to July 1970, covering the maximum phase of the current solar cycle at frequencies 2695, 4995 and 8800 MHz and their energy excesses have been examined in relation to the S-component of solar radio emission. The average slowly varying component has been determined by the superposed epoch method commonly known as the Chree analysis. Similar treatment of the bursts, data, mentioned above has been made to examine any probable 27-day variation and the results obtained have been compared with that of the S-component. Further, spectra of the microwave bursts under the so-called spectral type - inverted U, particularly those having a peak at 4995 MHz, have also been examined and compared with the average spectrum of the S-component. Some of the important results obtained from the present analysis are: (1) the nature of variation of both the average number of occurrences and energy excesses of the microwave bursts follow in general the average 27-day variation of the S-component, (2) the number of occurrences and energy excesses of the microwave bursts are comparatively greater in the ascending phase of the 27-day cycle than those in the descending phase, (3) bursts at progressively higher frequencies originate at lower levels in the solar atmosphere than those of the associated S-component, and (4) the average spectrum of the microwave bursts of inverted U spectral type having a peak at 4995 MHz is quite identical in nature to that of the S-component.  相似文献   

Constraints upon models of greenstone belt evolution by gravity modelling,Birch-Uchi greenstone belt,northern Ontario     

V.K. Gupta  P.C. Thurston  T.H. Dusanowskyj 《Precambrian Research》1982,16(4):233-255

Eight two-dimensional gravity models, incorporating most of the major hypotheses proposed for the development of Precambrian greenstone belts, are computed. Maximum use is made of geological and geophysical constraints, in an attempt to explain the disparity between the 11 000 m measured stratigraphic thickness and the maximum 5000 m interpreted vertical extent of a portion of the Birch-Uchi metavolcanic-metasedimentary belt.The two-dimensional modelling concentrates on an east-trending profile across a dominantly volcanic portion of the belt comprising three superposed basalt to rhyolite cycles. It is supplemented by a computed second vertical derivative map of the gravity field.Metamorphic and geophysical considerations show simple, isoclinal, parallel folding of the mapped stratigraphic thickness to be unacceptable. Proposed mechanisms which could explain the shallow interpreted vertical extent are a density gradient, a granite root, more complex folding of the belt and restriction of the metavolcanic basin. Taken individually, however, none of these mechanisms is entirely adequate.The model which best fits the gravity and geological data suggests that the shallow vertical extent is the result of both magmatic stoping by a subjacent granitic magma chamber during the caldera stage of cycle III volcanism and partial melting of the basaltic rocks during earlier cycles of volcanism.  相似文献   

Dispersion characteristics of low-latitude whistlers     

G. P. Gupta  R. N. Singh 《Planetary and Space Science》1977,25(12):1087-1092

The effect of ions on whistler dispersion characteristics has been studied. It is shown that the significant changes in the dispersion characteristics of low-latitude whistlers are brought about by the presence of ions. The dispersions for Nainital (geomagnetic lat. 19°1'N) and Gulmarg (geomagnetic lat. 24°10'N) are found to peak around 800 Hz. The short whistler sonograms recorded at Nainital and Gulmarg have been analysed, using the complete dispersion equation and the effect of ions has been shown. At higher frequencies the dispersion is found to decrease steadily and becomes independent of ions. Some examples of short whistlers have been found whose characteristics do not conform to the general trend of low-latitude whistlers, and, on the other hand, these whistlers show a constant dispersion unaffected by ions up to a fairly low frequency and thereafter decrease sharply at lower frequencies.  相似文献   

Study of the delta-Scuti star HR 1170     

S. K. Gupta 《Astrophysics and Space Science》1977,48(1):199-206

The light and colour curves of the δ-Scuti star HR 1170 are presented. The absolute and bolometric magnitudes are derived and the position of the star on the colour-colour diagram is also shown. The primary and beat periods estimated from the light curves are 0 _. ^d 098 299 and 0 _. ^d 392 06, respectively.  相似文献   

Green's function of one group transport equation for a finite slab of passive and multiplying media by Wiener-Hopf technique     

S. K. Bishnu  S. R. Das Gupta 《Astrophysics and Space Science》1992,196(1):65-100

We have applied the method of Wiener-Hopf technique to obtain the Green's functions of one-group transport equations (with anisotropic unit plane source and with isotroic unit plane source) for a finite slab of passive and multiplying media.  相似文献   

The Sq current system during the International Geophysical Year     

S. R. C. Malin  J. C. Gupta 《Geophysical Journal International》1977,49(2):515-529

Summary. The daily variation for the mean of the eight most quiet days of the IGY is represented as a function of latitude, longitude and UT by means of a spherical harmonic model. The most appropriate choice of Sq baseline is investigated, on the assumption that the external electric currents deduced from the model should be negligible at local midnight. The properties of the final model are discussed, particularly with regard to the external current foci, and are compared with those of previous models.  相似文献   

On Charged Analogues of Buchdahl’S Type Fluid Spheres     

Y.?K.?Gupta  Mukesh?KumarEmail author 《Astrophysics and Space Science》2005,299(1):43-59

In this article the charged analogues of recently derived Buchdahl’s type fluid spheres have been obtained by considering a particular form of electric field intensity. In this process, Einstein–Maxwell field equations yield eight different classes of solutions, joining smoothly with the exterior Reissner–Nordstrom metric at the pressure free intersurface. Out of the eight solutions only seven could be utilized to represent superdense star models with ultrahigh surface density of the order 2×10¹⁴ gm cm⁻³. The maximum masses of the star models were found to be 8.223931M_Θ and 8.460857M_Θ subject to strong and weak energy conditions, respectively, which are much higher than the maximum masses 3.82M_Θ and 4.57M_Θ allowed in the neutral cases. The velocity of sound seen to be less than that of light throughout the star models.  相似文献   

Some studies on solar microwave bursts in relation to the phases of the associated Hα-flares and their spectral nature     

S. K. Sarkar  T. Chattopadhyay  M. K. Das Gupta 《Solar physics》1975,40(2):411-415

Occurrences of the flare-associated microwave bursts as well as their peak flux and energy excess spectra have been examined in relation to the pre- and post-maximum phases of the respective flares during the period 1969–72. Results obtained are: (i) about 76% of the flare-associated bursts occur in the pre-maximum phase and the remaining 24% occurs in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise; (ii) ‘impulsive’ and ‘gradual rise and fall’ bursts are relatively more important in the pre-maximum phase while ‘post burst increase’ bursts show comparatively higher occurrences in the post-maximum phase; (iii) peak flux and energy excess spectra of the concurrent microwave bursts in the pre-maximum phase of the flare are mostly of ‘inverted U’ and ‘increasing with frequency’ spectral types. Of these, ‘impulsive’ bursts are predominantly of the ‘inverted U’ and the ‘grf’ bursts are of the ‘increasing with frequency’ spectral type.  相似文献   

Errata     

B.V. Krishna MurthyK. Sen Gupta 《Planetary and Space Science》1972

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