NISCAIR Online Periodicals Repository Community: BVAAP Vol.18 [2010]

Effect of solar activity on 8446 Å and 7320 Å airglow emissions

Title: Effect of solar activity on 8446 Å and 7320 Å airglow emissions

Authors: Krishna, M V Sunil; Singh, Vir

Abstract: The atomic oxygen airglow emission at 8446 Å and 7320 Å occurs at nearly 180 – 220km altitude region. These emissions occur due to solar EUV radiation and are very sensitive to the solar EUV flux. These emissions can provide valuable information about the atomic oxygen density and solar activity. We have developed a comprehensive model to study these emissions with the varying solar activity. These two emissions are studied with the help of the newly introduced Solar Irradiance Platform which gives the absolute values of solar flux for any given date and time. We present the results of modeling done over the present solar cycle, starting from 2001 which was an year of solar maximum. For the sake of modeling a mid latitude station at 35N 45E is chosen and the day of the year is chosen to be 3rd April. The results of intensity arepresented as a function of F10.7 flux index. The results show a very strong dependence over this index.

Page(s): 178-180

Thermal effect of radio frequency radiation

Title: Thermal effect of radio frequency radiation

Authors: Pathak, P P; Tripathi, H K

Abstract: In the present scenario the use of radio communication has extensively increased. The main examples are mobile phones, radio, television,radars etc. Especially, with the excessive use of mobile phones, the whole atmosphere has filled with radio waves. The emitted waves from the tower of radio, T.V. and mobile phones play a significant role in affecting the life of human beings. These waves are harmful for everybody,especially humans, because waves produce thermal effect in living cells. This increases temperature, which depends upon the heat emitting capacity of the body. Due to the excessive thermal effect in the area of radio frequency, the natural cooling system of the body is overcome.The cells with less flow of blood are mostly affected; the eye lenses are the good examples to show this effect. Development of womb and memory power is also affected by the radio frequency radiation. According to calculations, this thermal effect mainly depends on the distance of radiating antenna. This effect can be seen to its extreme in the range of 300 meter from the radio frequency tower. Therefore, some guidlines must be followed such as the building, school, hospital and any social activity should be kept away from the area. Some instruments should be fixed which could absorb these harmful waves or reduce this effect.

Page(s): 175-177

Dust storm detection and monitoring using multi-temporal Insat-3A-CCD data

Title: Dust storm detection and monitoring using multi-temporal Insat-3A-CCD data

Authors: Sanwlani, Nivedita; Chauhan, Prakash

Abstract: Sand and dust on being agitated up by winds often trigger huge dust storms and cause conditions of near-zero visibility. The local climatic conditions get altered by the airborne particles, from dust storms, by intercepting sunlight and modifying the energy budget through their ensuing behaviour of cooling and heating of the atmosphere. It is, therefore, essential to evolve proficiency in monitoring dust storms and predicting their evolution. Many studies using MODIS and other satellite data sets have shown importance of satellite imagery to detect and monitor the dust storms. However, the geostationary platform is the most suitable one to study the dynamics behaviour of such events. In the present study we have used INSAT-3A-CCD data to characterize a massive dust storm event occurred during October 15-16, 2008 over the northern Arabian Sea. The dust storm generated by strong winds lifts particles of dust or sand into air and is characterized by high Aerosol Optical Depth (AOD), lower angstrom exponent (a) along with near zero visibility condition. Multi temporal INSAT–3A–CCD data for every hour have been used to study the characteristics and transport of this dust storm event. AOD and a estimation were carried out and estimated AOD and a were also compared with MODIS derived AOD at 550nm and a (550/865). Air mass back-trajectory analysis was also conducted, along with the Quickscat scatterometer derived wind vector data, to identify potential source regions of these aerosols. An increase of the AOD values by 150-300% and simultaneous decrease of the angstrom exponent by 50 to 60 % was observed for dust-affected regions.Average AOD at 550nm was found to be 1.03, whereas, angstrom exponent was found to be 0.26 in comparison to AOD (550nm) of 0.33 and a of 0.4 during non-dust days. Higher AOD associated with lower angstrom exponents typically signifies presence of larger particles. Diurnal variations in AOD were also noticed an increment during dust storm, with 50% increase from morning to noon and 33% fall from afternoon to evening in the AOD at 550nm. Back trajectory analysis indicated that the dust was generated from the desert regions of Afghanistan and Pakistan and migrated towards the Arabian Sea.

Page(s): 168-174

Chemical analysis of ambient air particles and rain water in Agra : A study

Title: Chemical analysis of ambient air particles and rain water in Agra : A study

Authors: Saha, D; Gautam, Deepak; Chaudhary, Naresh; Yadav, Sudhanshu; Faisal, Md.; Yadav, Deepak Singh; Makhijani, S D; Kumar, Kamal

Abstract: The white marbled world heritage monument (about 350 years old) is famous world wide for its beauty and perfection. The Environmentscenario is changing due to industrialisation and urbanisation since 80’s decade. Leading to increase in air pollutants in the atmosphere, lookingin to the matter the Central Pollution Control Board (CPCB) has taken various steps in coordination with different departments for positivechange in environment and to examine the effects of steps taken. CPCB has carried out ambient air quality monitoring at four locations in Agracity since 2002. The pollutants respirable suspended particulate matter (RSPM), suspended particulate matter (SPM), sulphur di oxide (SO2)& oxides of nitrogen (NO2) are being monitored at four locations and analysed. The size of respirable suspended particles is less than 10μ andare generated mainly from dust particles, emission from petrol & diesel engine and industrial emission etc. Suspended particles are of the sizeless than 100μ and are mainly emitted from natural sources, sea salt, soil particles, smoke, fossil fuel and industrial emission. These particlessuspend in the atmosphere for longer duration. Sulphur-dioxide and oxides of nitrogen also reach to the atmosphere by different sources. TheData collected from 2002-2008 shows that there is a decrease in suspended particles along with decrease in non-respirable suspendedparticulate matter (long distance travelling particles), due to which improvement appears in air quality of Agra city. For the detailed study ofpollutants metrological data and mixing height from sodar is also included in the study.

Page(s): 165-167