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Search Results: 1 - 10 of 10 matches for " Devendraa Siingh "
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The role of cosmic rays in the Earths atmospheric processes
Devendraa Siingh,R. P. Singh
Physics , 2009, DOI: 10.1007/s12043-010-0017-8
Abstract: In this paper, we have provided an overview of cosmic ray effects on terrestrial processes such as electrical properties, global electric circuit, lightning, cloud formation, cloud coverage, atmospheric temperature, space weather phenomena, climate, etc. It is suggested that cosmic rays control short term and long term variation in climate. There are many basic phenomena which need further study and require new and long term data set. Some of these have been pointed out.
The mesospheric inversion layer and sprites
S. Fadnavis,Devendraa Siingh,R. P. Singh
Physics , 2009, DOI: 10.1029/2009JD011913
Abstract: The vertical structure of temperature observed by SABER (Sounding of Atmosphere using Broadband Emission Radiometry) aboard TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) and sprites observations made during the Eurosprite 2003 to 2007 observational campaign were analyzed. Sprite observations were made at two locations in France, namely Puy de Dome in the French Massif Central and at the Pic du Midi in the French Pyrenees. It is observed that the vertical structure of temperature shows evidence for a Mesospheric Inversion Layer (MIL) on those days on which sprites were observed. A few events are also reported in which sprites were not recorded, although there is evidence of a MIL in the vertical structure of the temperature. It is proposed that breaking gravity waves produced by convective thunderstorms facilitate the production of (a) sprites by modulating the neutral air-density and (b) MILs via the deposition of energy. The same proposition has been used to explain observations of lightings as well as both MILs and lightning arising out of deep convections.
Measurements of positive ions and air-earth current density at Maitri, Antarctica
Devendraa Siingh,V Pant,A K Kamra
Physics , 2009, DOI: 10.1029/2006JD008101
Abstract: Simultaneous measurements of the small-, intermediate- and large- positive ions and air earth current density made at a coastal station, Maitri at Antarctica during January to February 2005, are reported. Although, small and large positive ion concentrations do not show any systematic diurnal variations, variations in them are almost similar to each other. On the other hand, variations in intermediate positive ion concentrations are independent of variations in the small/large positive ions and exhibit a diurnal variation which is similar to that in atmospheric temperature on fair weather days with a maximum during the day and minimum during the night hours. No such diurnal variation in intermediate positive ion concentration is observed on cloudy days when variations in them are also similar to those insmall/large positive ion concentrations. Magnitude of diurnal variation in intermediate positive ion concentration on fair weather days increases with the lowering of atmospheric temperature in this season. Scavenging of ions by snowfall and trapping of Alha - rays from the ground radioactivity by a thin layer of snow on ground, is demonstrated from observations. Variations in intermediate positive ion concentration are explained on the basis of the formation of new particles by the photolytic nucleation process.
Electrodynamical Coupling of Earth's Atmosphere and Ionosphere: An Overview
A. K. Singh,Devendraa Siingh,R. P. Singh,Sandhya Mishra
International Journal of Geophysics , 2011, DOI: 10.1155/2011/971302
Abstract: Electrical processes occurring in the atmosphere couple the atmosphere and ionosphere, because both DC and AC effects operate at the speed of light. The electrostatic and electromagnetic field changes in global electric circuit arise from thunderstorm, lightning discharges, and optical emissions in the mesosphere. The precipitation of magnetospheric electrons affects higher latitudes. The radioactive elements emitted during the earthquakes affect electron density and conductivity in the lower atmosphere. In the present paper, we have briefly reviewed our present understanding of how these events play a key role in energy transfer from the lower atmosphere to the ionosphere, which ultimately results in the Earth's atmosphere-ionosphere coupling.
Electrodynamical Coupling of Earth's Atmosphere and Ionosphere: An Overview
A. K. Singh,Devendraa Siingh,R. P. Singh,Sandhya Mishra
International Journal of Geophysics , 2011, DOI: 10.1155/2011/971302
Abstract: Electrical processes occurring in the atmosphere couple the atmosphere and ionosphere, because both DC and AC effects operate at the speed of light. The electrostatic and electromagnetic field changes in global electric circuit arise from thunderstorm, lightning discharges, and optical emissions in the mesosphere. The precipitation of magnetospheric electrons affects higher latitudes. The radioactive elements emitted during the earthquakes affect electron density and conductivity in the lower atmosphere. In the present paper, we have briefly reviewed our present understanding of how these events play a key role in energy transfer from the lower atmosphere to the ionosphere, which ultimately results in the Earth's atmosphere-ionosphere coupling. 1. Introduction The atmosphere of the Earth is a layer of gases surrounding the Earth that is retained by Earth’s gravity. The atmosphere protects life on the Earth by absorbing the ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night. Based on temperature distribution, atmosphere is divided into the troposphere, stratosphere, mesosphere, and thermosphere. The temperature in the thermosphere remains almost constant (Figure 1) [1]. The stratosphere and mesosphere regions are also grouped as the middle atmosphere. The region above the middle atmosphere is called the upper atmosphere where solar radiation and other sources ionize the neutral constituents forming plasma of ions and electrons. The region extending from the mesosphere to the thermosphere is called ionosphere where plasma dynamics is controlled by the collisions between the ionized particles and neutrals as well as between the ionized particles themselves. The region above the ionosphere is known as the magnetosphere. In this region, charged particles dynamics is controlled by the Earth’s magnetic field because the density collision frequency is very low. There is no sharp boundary between the upper ionosphere and the lower magnetosphere region. Figure 1: Variation of temperature, electron density and electrical conductivity of various atmospheric layers, after [ 1]. The ionosphere system is mainly controlled by various external sources of forcing and number of mechanisms operative in the system to convert, transport, and redistribute the input energy. Solar extreme ultraviolet (EUV) radiation and particle energy from the sun in the form of precipitating solar wind plasma energetic particle influence from the above, while tides, planetary waves, gravity
Seasonal variation of the mesospheric inversion layer, thunderstorms and mesospheric ozone over India
S. Fadnavis,Devendraa Siingh,G. Beig,R. P. Singh
Physics , 2009, DOI: 10.1029/2006JD008379
Abstract: Temperature and ozone volume mixing ratio profiles obtained from the Halogen Occultation Experiment (HALOE) aboard the Upper Atmospheric Research Satellite (UARS) over India and over the open ocean to the south during the period 1991-2001 are analyzed to study the characteristic features of the Mesospheric Inversion Layer (MIL) at 70 to 85 km altitude and its relation with the ozone mixing ratio at this altitude. We have also analyzed both the number of lightning flashes measured by the Optical Transient Detector (OTD) onboard the MicroLab-1 satellite for the period April 1995 - March 2000 and ground-based thunderstorm data collected from 78 widespread Indian observatories for the same period to show that the MIL amplitude and thunderstorm activity are correlated. All the data sets examined exhibit a semiannual variation. The seasonal variation of MIL amplitude and the frequency of occurrence of the temperature inversion indicate a fairly good correlation with the seasonal variation of thunderstorms and the average ozone volume mixing ratio across the inversion layer. The observed correlation between local thunderstorm activity, MIL amplitude and mesospheric ozone volume mixing ratio are explained by the generation, upward propagation and mesospheric absorption of gravity waves produced by thunderstorms.
Measurements of the ion concentrations and conductivity over the Arabian Sea during the ARMEX
Devendraa Siingh,S. D. Pawar,V. Gopalakrishnan,A. K. Kamra
Physics , 2009, DOI: 10.1029/2005JD005765
Abstract: Measurements of the small-, intermediate-, and large-ion concentrations and the atmospheric electric conductivity of both polarities have been made over the Arabian Sea on four cruises of ORV Sagarkanya during the Arabian Sea Monsoon Experiment (ARMEX)during the monsoon and pre-monsoon seasons of 2002 and 2003. Seasonally averaged values of the total as well as polar conductivity are much higher during the monsoon than pre-monsoon season. Surprisingly, however, the concentration of small ions are less and those of large and intermediate ions are more during the monsoon than pre-monsoon season. The diurnal variations observed during the pre-monsoon season show that the nighttime small ion concentrations are about an order of magnitude higher than their daytime values. On the contrary, the daytime concentrations of the intermediate and large ions are much higher than those of their nighttime values. No such diurnal variations in ion concentrations are observed in monsoon season. Also examined are the variations in ion concentrations of different categories with distance from the coastline in different seasons and the ion-concentration changes associated with the precipitation of various types that occurred over ORV Sagarkanya. It is sufficient to invoke the ion-aerosol attachment process to explain our pre-monsoon observations. However, the generation of highly charged large ions by the bubble-breaking process caused by the wave breaking due to strong southwesterly surface winds ten to twenty meter per second over the Arabian Sea is postulated to explain the monsoon season observations.
The atmospheric global electric circuit: An overview
Devendraa Siingh,V. Gopalakrishnan,R. P. Singh,A. K. Kamra,Shubha Singh,Vimlesh Pant,R. Singh,A. K. Singh
Physics , 2009, DOI: 10.1016/j.atmosres.2006.05.005
Abstract: Research work in the area of the Global Electric Circuit (GEC) has rapidly expanded in recent years mainly through observations of lightning from satellites and ground-based networks and observations of optical emissions between cloud and the ionosphere. After reviewing this progress, we critically examine the role of various generators of the currents flowing in the lower and upper atmosphere and supplying currents to the GEC. The role of aerosols and cosmic rays in controlling the GEC and linkage between climate, solarterrestrial relationships and the GEC has been briefly discussed. Some unsolved problems in this area are reported for future investigations.
Thunderstorms, lightning, sprites and magnetospheric whistler-mode radio waves
Devendraa Siingh,A. K. Singh,R. P. Patel,Rajesh Singh,R. P. Singh,B. Veenadhari,M. Mukherjee
Physics , 2009,
Abstract: Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharges couple the lower atmosphere with the ionosphere/magnetosphere. Hence various features of these waves from ULF to VHF are reviewed with reference to recent results and their consequences are also briefly discussed.
Scavenging of atmospheric ions and aerosols by drifting snow in Antarctica
A. K. Kamra,Devendraa Siingha,Vimlesh Pant
Physics , 2009, DOI: 10.1016/j.atmosres.2008.02.018
Abstract: Measurements of the small,intermediate, and large ion concentrations and the airearth current density along with simultaneous measurements of the concentration and size-distribution of aerosol particles in the size ranges 4.4 to 163 nm and 0.5 to 20 micrometer diameters are reported for a drifting snow period after the occurrence of a blizzard at a coastal station, Maitri, Antarctica. Ion concentrations of all categories and the airearth current simultaneously decrease by approximately an order of magnitude as the wind speed increases from 5 to 10 meter per sec. The rate of decrease is the highest for large ions, lowest for small ions and in between the two for intermediate ions. Total aerosol number concentration decreases in the 4.4 to 163 nm size range but increases in 0.5 to 20 micrmetr size range with wind speed. Size distribution of the nanometer particles show a dominant maximum at 30 nm diameter throughout the period of observations and the height of the maximum decreases with wind speed. However, larger particles show a maximum at 0.7 micrometer diameter but the height of the maximum increases with increasing wind speed. The results are explained in terms of scavenging of atmospheric ions and aerosols by the drifting snow particles.
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