http://nopr.niscpr.res.in/handle/123456789/36923 2026-10-13T02:13:49Z 2026-10-13T02:13:49Z Sen, A K Saha, B Trehan, S K Sehra, J S http://nopr.niscpr.res.in/handle/123456789/37240 2016-11-22T09:23:15Z 1979-10-01T00:00:00Z

Title: Precursor of Solar Flare Effects in If & hf Bands Authors: Sen, A K; Saha, B; Trehan, S K; Sehra, J S Abstract: A simultaneous observation of solar flare effects in the If and hf' bands made in Calcutta (lat., 22°34'N; long., 88°24' E) revealed that prior to the sudden attack of an event a slower change of level occurs in a great majority of cases. Such a precursor is particularly noticeable in the If band appearing in the form of a longer duration absorption background superimposed on a solar flare effect. Analysis of the data indicates a connection of the precursor with flare X-rays in the wavelength ranges 1-8Å and 8-20 Å. The results are critically examined in the light of the current knowledge about flare ionization mechanisms. Page(s): 418-422

1979-10-01T00:00:00Z Kaul, R K Razdan, H http://nopr.niscpr.res.in/handle/123456789/37239 2016-11-22T09:21:27Z 1979-10-01T00:00:00Z

Title: Geomagnetic Activity & the Effect of Tau X-Ion the D-Region Authors: Kaul, R K; Razdan, H Abstract: Data from a 164 kHz long wave propagation experiment at Gulmarg are analyzed to study the effect of X-rays from Tau X-Ion the D-region ionization. Increased absorption of the 164 kHz waves, corresponding to increased ionization at the time of the transit of Tau X-lover the reflection point, is observed consistently during 1975-77. The absorption suffered by the radio waves at the time of the meridian transit of the source is shown to depend inversely on the level of geomagnetic activity, the absorption being negligibly small on magnetically disturbed days. This dependence of absorption on geomagnetic activity is explained as being due to a possible geomagnetic dependence of NO concentration at D-region heights. Page(s): 414-417

1979-10-01T00:00:00Z Marar, T M K Iyengar, V S Kasturirangan, K Rao, U R http://nopr.niscpr.res.in/handle/123456789/37238 2016-11-22T09:19:20Z 1979-10-01T00:00:00Z

Title: On the Characteristics of Line Emissions from, Binary X-ray Sources & Supernova Remnants Authors: Marar, T M K; Iyengar, V S; Kasturirangan, K; Rao, U R Abstract: X-ray spectroscopy of celestial X-ray sources can yield extremely interesting results on the physical conditions and processes that are responsible for the emission from these sources. Iron line emission at about 6'8 keV from many supernova remnants and X-ray binaries has already been observed by several workers, In this paper we present the available data on iron line emission from Tycho, Cas A and Her X-1 and discuss the implications. Page(s): 411-413

1979-10-01T00:00:00Z Iyengar, V S Marar, T M K Kasturirangan, K Rao, U R http://nopr.niscpr.res.in/handle/123456789/37237 2016-11-22T09:17:46Z 1979-10-01T00:00:00Z

Title: A New Technique for Rejection of uv Background in Soft X-ray Proportional Counters Authors: Iyengar, V S; Marar, T M K; Kasturirangan, K; Rao, U R Abstract: Proportional counters used for observations of celestial X-ray sources in the energy range 0'1-1 keV often employ thin plastic films as entrance radiation windows. Ultraviolet background in these counters causes considerable difficulty in obtaining low sensitivities, A new technique for the rejection of ultraviolet background by the use of a wire grid placed a few mm below the window and maintained at a suitable negative potential, is presented. Results of experiments conducted on a laboratory model of a counter employing this technique are presented. Page(s): 408-410

1979-10-01T00:00:00Z