http://nopr.niscpr.res.in/handle/123456789/36934 2026-10-13T04:06:45Z 2026-10-13T04:06:45Z Jain, A R Deshpande, M R Sethia, G Rastogi, R G Singh, Malkiat Gurm, H S Janve, A V Rai, R K http://nopr.niscpr.res.in/handle/123456789/37338 2016-11-23T07:06:21Z 1978-10-01T00:00:00Z

Title: Geomagnetic Storm Effects on Ionospheric Total Electron Content in Indian Zone - Part II : Evidence of Equatorial Electrojet Control through Fountain Effect Authors: Jain, A R; Deshpande, M R; Sethia, G; Rastogi, R G; Singh, Malkiat; Gurm, H S; Janve, A V; Rai, R K Abstract: Observations of ionospheric total electron content (TEC) for four stations in the equatorial anomaly region and for live major storms are analyzed in conjunction with <i>f</i>₀F2 data of the equatorial station Trivandrum and the index of the strength of equatorial electrojet determined using ground-based magnetic data for Trivandrum and a low-latitude station Alibag. It is shown that qualitatively the variations in equatorial electrojet intensity are responsible for the significant daytime storm effects in TEC at these latitudes. Evidence of the "fountain effect" On storm days is provided by (i) significant negative correlation between electrojet strength and <i>N</i>_mF2 for Trivandrum and (ii) significant negative correlation between changes in <i>N</i>_mF2 for Trivandrum and change in the TEC at stations in anomaly region with diffusion time equal to 2 hr. The results suggest that changes in E X B drift contribute significantly to daytime storm effects in TEC at stations in the anomaly region. Some abnormal increases in TEC which could not be explained on the basis of E X B drifts are suggested to be due to the effects of equatorial winds from higher latitudes during the geomagnetically disturbed periods. Page(s): 254-261

1978-10-01T00:00:00Z Chandra, H Rastogi, R G http://nopr.niscpr.res.in/handle/123456789/37336 2016-11-23T06:57:06Z 1978-10-01T00:00:00Z

Title: Nature of Equatorial Spread-F Irregularities Derived from Spaced Fading Records at Thumba Authors: Chandra, H; Rastogi, R G Abstract: Spaced fading records of nighttime F-region echoes over Thumba are compared on spread-F days and non-spread-F days. The fading rate is considerably low on non- spread-F days. The daytime westward drift (or the eastward electric field) reversed about one hour later on spread-F days than on non-spread-F days. Diffraction patterns due to the irregularities associated with the spread-F are more closely field-aligned with higher elongation and smaller E-W size than those on non-spread-F days. It is suggested that the necessary condition for equatorial spread in the evening hours is the persistence of eastward electric field after the sunset for duration long enough to trigger the irregularities. Page(s): 266-268

1978-10-01T00:00:00Z Dixit, S D Ghosh, S N http://nopr.niscpr.res.in/handle/123456789/37335 2016-11-23T06:53:11Z 1978-10-01T00:00:00Z

Title: Quenching of NO₂ Continuum by Ar CO₂ & NH₃ Authors: Dixit, S D; Ghosh, S N Abstract: The dynamic flow method has been used to investigate the quenching of NO. Continuum by Ar, CO₂ and NH8 gases. The K/A ratio, where K is the two-body quenching rate coefficient and A is the transition probability of NO₂ continuum, has been obtained as 6·0 X 10^-16, 1·1 X 10^-16 and 5·7 x 10^-17, cm³ for quenching by Ar, CO₂ and NH₃ respectively. Page(s): 265-266

1978-10-01T00:00:00Z Chandra, H Vyas, G D http://nopr.niscpr.res.in/handle/123456789/37333 2016-11-23T06:50:00Z 1978-10-01T00:00:00Z

Title: Magnetic Activity & Spread-F at Kodaikanal Authors: Chandra, H; Vyas, G D Abstract: Occurrence of spread-F at Kodaikanal for the period 1956-66 is examined in relation to the geomagnetic disturbance index <i>K_p</i>_.Consistent decrease in the percentage occurrence of spread-F in the pre-midnight hours (2000-2300 hrs LT) is noted during the period of high solar activity only. For the low solar activity period the decrease is noticed only during equinoxes and an increase rather than a decrease is noticed during summer months. The mean spread-F occurrence in the pre-sunrise hours (0300-0500 hrs LT) is nearly independent of <i>K_p.</i> Page(s): 263-265

1978-10-01T00:00:00Z