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S. N. Tandon J. B. Hutchings S. K. Ghosh A. Subramaniam G. Koshy V. Girish P. U. Kamath S. Kathiravan A. Kumar J. P. Lancelot P. K. Mahesh R. Mohan J. Murthy S. Nagabhushana A. K. Pati J. Postma N. Kameswara Rao K. Sankarasubramanian P. Sreekumar S. Sriram C. S. Stalin F. Sutaria Y. H. Sreedhar I. V. Barve C. Mondal S. Sahu 《Journal of Astrophysics and Astronomy》2017,38(2):28
The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within \(\sim \)15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of \(1.8^{\prime \prime }\) and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results. 相似文献
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Analysis of the intensity maps of Fexiv emission at =5303 Å obtained from the observations of ground-based coronagraphs during the sunspot minimum period 1985 and 1986 shows the persistent presence of localized strong emissions. Typical emission intensities associated with the active regions were found to be about 5 to 20 times stronger than the unperturbed corona. Using Stanford magnetograms we identified strong magnetic field gradients in those active regions, with a minimum threshold gradient of 3 × 10–5 G km–1, associated with such strong emissions. From our sample we infer that the flux emergence within or in the vicinity of a persistent active region seems to play an important role in the activity associated with the enhancement in 5303 Å emission. 相似文献
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Analysis of the photospheric and chromospheric activity at the sites of enhanced 5303 Å coronal intensity revealed some important aspects of their association. We have examined the daily maps of 5303 Å coronal line intensity of Lomnický tít for the low sunspot activity years 1985 and 1986 in association with the cotemporal daily maps of sunspots, plages and Stanford magnetograms and identified strong field gradients at the sites of enhanced intensity regions. We found that the peak intensity does not depend on the strength of the underlying magnetic field though the coronal intensity-enhanced feature is almost sure to occur at the locations of sunspots with strong magnetic fields and at the locations of plages having larger areas. 相似文献
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To study the evolution of large convective cells known as supergranules, a solar telescope was set up at Maitri, Indian permanent station in Antarctica region, during the local summer months (December 1989 through March 1990). A continuous sequence of calcium K-line filtergrams for 106 hours spaced at intervals of about 10 min was obtained. The analysis of the data indicates that the most probable lifetime of the calcium-K network is about 22 hours. The lifetime depends upon the size of the cell and is larger for bigger cells. The data also show that cells (of a given size) associated with remnant magnetic field regions live longer than those in the field-free region. This may mean that the magnetic field plays an important role in the confinement of these structures. 相似文献
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