http://nopr.niscair.res.in/handle/123456789/11649 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11655 Title: Characteristics of mobile satellite L-band signal in mid-latitude region: GPS approach <br/> <br/>Authors: Pai, B Voon; Abidin, W A W Z; Othman, A K; Zen, H; Masri, T <br/> <br/>Abstract: Mobile satellite L-band signal that propagates from the transmitting satellite to the receiver experiences impairment mainly due to shadowing and multipath effects. In the present study, open space data has been obtained for Fukuoka, Japan (mid-latitude) using portable global positioning system (GPS) satellite receiver. The received signal performance, fading characteristic and cumulative distribution function of certain GPS satellites over the sky of Fukuoka have been observed and analysed. A general mathematical model representing the signal strength for the open space environment has been deduced based on the collected data. The outcome of this study can be used in future research to determine the effect of different mobile satellite environment on the arriving mobile satellite signal in improving the quality of service perceived by mobile satellite users. <br/> <br/>Page(s): 105-112 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11654 Title: Characterization of PM, PM₁₀ and PM_2.5 mass concentrations at a tropical semi-arid station in Anantapur, India <br/> <br/>Authors: Balakrishnaiah, G; Kumar, K Raghavendra; Reddy, B Suresh Kumar; Gopal, K Rama; Reddy, R R; Reddy, L S S; Narasimhulu, K; Ahammed, Y Nazeer; Balanarayana, C; Moorthy, K Krishna; Babu, S Suresh <br/> <br/>Abstract: The particulate matter (PM), PM₁₀ and PM_2.5 concentrations are estimated from regular measurements of size segregated as well as total mass concentration of near surface composite aerosols, using a ten-channel Quartz Crystal Microbalance (QCM) Cascade Impactor in a tropical semi-arid station, Anantapur, India for the period May 2006 – April 2007. The monthly variations of PM, PM₁₀ and PM_2.5 and season-wise shares of PM₁₀ and PM_2.5to PM have been computed. The highest contribution of PM₁₀ to PM has been noticed during local summer season, while the maximum share of PM_2.5 to PM has been noticed during the winter season. The average values of PM, PM₁₀ and PM_2.5 mass concentrations have been found to be 21.21±1.21, 18.7±1.06 and 17.02±1.28 <img src='/image/spc_char/micro.gif' border=0> g m^-3, respectively. Seasonally, the concentration has been highest in winter (24.62±3.53, 22.07±2.56, 21.29±2.31) and lowest in monsoon (18.12±1.62, 16.46±1.82, 14.47±1.57) for PM, PM₁₀ and PM_2.5, respectively. The back trajectory cluster analysis revealed that the aerosol loading has been significantly higher in fine mode during periods of continental air mass (winter) but when the winds shift to marine (monsoon), the loading became higher due to major contribution of sea salt aerosols, particularly in the coarse mode. PM₁₀ and PM_2.5concentrations has been highly correlated with PM and inversely correlated with local wind speed. The results of this analysis underlined the importance of local emission sources, mostly from anthropogenic, which are responsible for the high PM₁₀ and PM_2.5 concentration levels observed during this one year - sampling period. <br/> <br/>Page(s): 95-104 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11653 Title: Atmospheric turbidity over a continental station Mysore, India <br/> <br/>Authors: Ganesh, K E; Umesh, T K; Narasimhamurthy, B <br/> <br/>Abstract: The solar radiation is collected at five optical channels at a continental station Mysore, India during December 2003 - June 2006 using a portable sunphotometer MICROTOPS II. Angstrom’s turbidity parameters, <img src='/image/spc_char/alpha.gif' border=0> and <img src='/image/spc_char/beta.gif' border=0>, have been calculated and analysed on daily, monthly, seasonal and annual basis. The observations show that <img src='/image/spc_char/alpha.gif' border=0> and <img src='/image/spc_char/beta.gif' border=0> vary throughout on individual day because of changes in the atmospheric meteorological parameters. It is observed that <img src='/image/spc_char/beta.gif' border=0> is highest during summer and lowest during winter. An anti-correlation between <img src='/image/spc_char/alpha.gif' border=0> and <img src='/image/spc_char/beta.gif' border=0> is observed throughout the day during all seasons indicating continuous redistribution of fine and coarse particles under the influence of meteorological parameters. The yearly comparison of <img src='/image/spc_char/alpha.gif' border=0> and <img src='/image/spc_char/beta.gif' border=0> along with the atmospheric visibility is also analysed and presented in the paper. <br/> <br/>Page(s): 85-94 Tue, 29 Mar 2011 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/11652 Title: Directional muon telescopes not useful for estimating the magnitudes of Forbush decreases and geomagnetic storms <br/> <br/>Authors: Kane, R P <br/> <br/>Abstract: When a coronal mass ejection (CME) escapes from the Sun and spreads in interplanetary space as a blob (termed as interplanetary CME, ICME), galactic cosmic rays (CR) passing through the same get modulated and one can detect anisotropies in data of muon directional telescopes located on the Earth. For 15 severe storms (Dst < -200 nT) during solar cycle 23 (1996-2006), the hourly data for Nagoya muon directional telescopes showed that for each one of these storms, there were anisotropies in one or more of the 16 directional telescopes. The maximum magnitudes of the anisotropies were ~1% or less and had reasonably good relationships (correlation +0.75) with the magnitudes of the following Forbush decrease (FD) in the muons in the vertical direction V (muon V) and also in CR neutron monitor (NM) data at Climax, Colorado, USA. But a correlation of ~0.75 implies a variance explained (square of correlation) of only ~55%, leaving ~45% as random component. With geomagnetic Dst(min), the muon anisotropy magnitudes had a still lower correlation (+0.44±0.20), which would imply a variance explained of only ~20%, leaving ~80% as random component, resulting in regression prediction errors exceeding 50%. Thus, the anisotropies were only a rough indicator of there being some anomalous structure out in the interplanetary space, but the magnitudes of the anisotropies could not give any accurate indication of the magnitudes of the Forbush decreases that may follow, much less for the magnitudes of the geomagnetic storm Dst(min) that may follow. <br/> <br/>Page(s): 76-84 Tue, 29 Mar 2011 22:58:59 GMT