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21.
Meena Pokharia Lalan Prasad Chandrasekhar Bhoj Chandni Mathpal 《Journal of Astrophysics and Astronomy》2018,39(5):53
The aim of this paper is to investigate the association of the geomagnetic storms with the magnitude of interplanetary magnetic field IMF (B), solar wind speed (V), product of IMF and wind speed (\(V \cdot B)\), Ap index and solar wind plasma density (\(n_{\mathrm{p}})\) for solar cycles 23 and 24. A Chree analysis by the superposed epoch method has been done for the study. The results of the present analysis showed that \(V \cdot B\) is more geoeffective when compared to V or B alone. Further the high and equal anti-correlation coefficient is found between Dst and Ap index (? 0.7) for both the solar cycles. We have also discussed the relationship between solar wind plasma density (\(n_{\mathrm{p}})\) and Dst and found that both these parameters are weakly correlated with each other. We have found that the occurrence of geomagnetic storms happens on the same day when IMF, V, Ap and \(V \cdot B\) reach their maximum value while 1 day time lag is noticed in case of solar wind plasma density with few exceptions. The study of geomagnetic storms with various solar-interplanetary parameters is useful for the study of space weather phenomenon. 相似文献
22.
Near infrared coronal line emission at 1.98 ± 0.02Μm due to [Si VI] detected in the spectrum of Nova Herculis 1991 about 17
days after optical maximum is reported. The early appearance of coronal emission is yet another unusual feature of this fast
nova in which early onset of dust formation processes and X-ray detection five days after outburst have already been reported.
The coronal line observations reported here are consistent with X-ray detection and support a hot shocked circumstellar envelope
at the periphery of the dust formation zone in the nova. 相似文献
23.
High speed photometry during the lunar occultation of a stellar system provides an effective means of achieving high angular
resolution in one dimension at the sub arc second level which is well suited for resolving close binary projected separations
in the range of 10–100 milliarc seconds. An optical fast photometer designed for such a purpose is described and some results
from the initial observations taken with the system including the resolution of a projected separation of 55 milli arcsecond
in one binary system are detailed. 相似文献
24.
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26.
S. Chandrasekhar 《Journal of Astrophysics and Astronomy》1994,15(2):105-109
The density of the white dwarf stars is reconsidered from the point of view of the theory of the poly tropic gas spheres,
and gives for themean density of a white dwarf (under ideal conditions) the formula ρ=2.162 × 106 × (M/⊙)2.
The above formula is derived on considerations which are a much nearer approximation to the conditionsactually existent in a white dwarf than the previous calculations of Stoner based on uniform density distribution in the star and which gave
for the limiting density the formula ρ=3.977 × 106 × (M/⊙)2. 相似文献
27.
S. Chandrasekhar 《Journal of Astrophysics and Astronomy》1994,15(2):115-116
The theory of thepolytropic gas spheres in conjunction with the equation of state of arelativislically degenerate electrongas leads to aunique value for the mass of a star built on this model. This mass (=0.9I⊙) is interpreted as representing the upper limit to the mass of an ideal white dwarf. 相似文献
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29.
Jatin Rathod Girija Rajaram Radharani Alyana A. Chandrasekhar Reddy D. S. Misra C. G. Patil M. Y. S. Prasad A. G. Ananth 《Journal of Astrophysics and Astronomy》2008,29(1-2):293-302
In the present study, we investigate the possible relationship of IP parameters of solar wind and interplanetary magnetic field with ground-based geomagnetic indices. To carry out the study, we take all the IP shock events listed by Proton Monitor onboard Solar and Heliospheric Observatory (SOHO) during 2005, and plot the time variations of all the IP parameters and geomagnetic parameters (±5 days), centered at the shock arrival time. Next, we obtain scatter plots of absolute values of solar wind parameters such as Vsw, Nsw and Interplanetary Magnetic Field (IMF) components Bx, By, Bz and total B with the values of geomagnetic parameters such as Dst, Kp indices, dayside Magnetopause (MP) distance and Cosmic-Ray Neutron Monitor count (CRNM). The scatter plots show that before the IP shock, the pattern is random with no clear relationship. Following the shock, a clear pattern emerges with a type of relationship being seen — clear for SHARP shocks and less clear for DIFFUSE shocks. A total of 10 shock events for 2005 have been studied. Typical examples of this behaviour are the shock events of January 21, 2005 and May 15, 2005. Our study suggests a definite correlation between changes in the solar wind and interplanetary magnetic field parameters and ground-based geomagnetic response. We are trying to obtain quantitative relationships between these for shock events of 2005. 相似文献
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