Rocket measurements of ozone concentrations in the stratosphere and mesosphere over Thumba

A rocket-borne solar middle ultraviolet photometer has been developed at the Physical Research Laboratory, Ahmedabad for the measurement of ozone concentrations at stratospheric and mesospheric heights. The instrument has now been flown successfully several times from thumba and ozone concentrations determined over an altitude range of 15 to 80 km. This paper describes the instrumentation, data analysis technique as well as the laboratory calibration procedures. Also presented are the results from four successful rocket experiments conducted during equinoctial months under an Indo-USSR collaborative programme for strato-mesospheric studies. The results show that at Thumba peak ozone concentrations vary between 2·2 and 3·1×10¹² molecules per cc and the peak altitude varies from 25 to 29 km from flight to flight. In the altitude region above about 40 km the ozone concentrations over Thumba are lower than the standard mid-latitude model values, by a factor lying between 1·5 and 2·5.     

Measurement of nitric oxide and related parameters in the equatorial mesosphere and lower thermosphere

A sounding rocket was launched in March 1982 from Thumba, India, shortly after sunrise. The measurements included the concentration of nitric oxide and ozone, the total ion density and the Lyman-α flux. Hence most parameters important for the formation of the D-region during daytime are available with the exception of solar radiation other than Lyman-α which only becomes important above 95 km. The mutual agreement is satisfactory which adds weight to the measurements.     

Studies on urban heat islands using envisat AATSR data

Urbanization has significant effects on local weather and climate and among these effects one of the most familiar is the urban heat island, for which the temperatures of the central urban locations are several degrees higher than those of nearby rural areas of similar elevation. Satellite data provides important inputs for estimating regional surface albedo and evapotranspiration required in the studies related to surface energy balance. Present study describes the analysis of day and night ENVISAT-AATSR satellite data for Urban heat island and surface thermal inertia. Field campaigns have been conducted in synchronous with the satellite data over pass for validating the surface temperature estimated from AATSR data. Satellite derived surface temperature values are within ±1° C from ground measured values. Heat island formations in urban regions of Hyderabad and environs can be clearly seen in the night time data with core urban regions showing high temperatures. Apparent thermal inertia derived from AATSR day and night data sets have shown typical variations over urban regions.     

New method of analysis for TeV gamma-ray data collected by the TACTIC telescope

We describe a new fractal and wavelet based framework for analysing atmospheric Cerenkov images of extensive air showers. The methodology developed using simulated data has been tested with the data collected from Mrk421 and Crab nebula directions during 10 October 2009–16 May 2010 by the TACTIC telescope. The telescope detected flaring activity in TeV gamma-rays from Mrk421 during 15th-17th February 2010. Hillas parameter analysis of Cerenkov images showed presence of TeV γ-ray signal with statistical significance of 12.5 σ beyond 1TeV energy for the 265 hours data set. Based on a Monte-Carlo simulated database of Cerenkov images recorded by the TACTIC telescope, the wavelet dimension B₆ can be exploited as a useful parameter to segregate gamma-ray initiated events from hadron initiated events with better efficiency. We derive a preliminary value of the relevant significance for gamma initiated events using wavelet parameter B₆ for the 265 hours long observation spell of Mrk421 including the flaring episode during 15th–17th February 2010 and 66 hours data of observations on Crab nebula. Wavelet analysis approach has also been tested on Crab OFF- source data of 27 hours. Application of wavelet parameter B₆ on the recorded Cerenkov images of the TACTIC telescope reveals better results in terms of segregation efficiency and enhancement of the determined value of statistical significance as compared to the Hillas parameters approach.     

几种主要固沙措施的价值分析

以甘肃民勤沙区为例,采用ABC分析法选取了当地6种主要固沙措施,将其功能分解为主要功能和次要功能。主要功能定义为固阻流沙的功能,以1-蚀积系数表示;次要功能定义为改善土壤理化性质的功能,以增加土壤有机质、全氮量和<0.1mm的沙粒的相对值表示,调查计算了固沙措施功能周期内的全部成本,从功能和成本两方面进行了价值分析,为选用固沙效果显著且投资相对低廉的固沙措施提供科学依据。     

Fine-grained volatile components ubiquitous in solar nebula: Corroboration from scoriaceous cosmic spherules

The scoriaceous cosmic spherules (CSs) that make up to a few percent (for sizes >150 μm size) of total micrometeorite flux are ubiquitous and have remained enigmatic. The present work provides in-depth study of 81 scoriaceous CSs, from observed ~4000 CSs, collected from Antarctica (South Pole water well) and deep-sea sediments (Indian Ocean) that will allow us to analyze the nature of these particles. The fine-grained texture and the chemical composition of scoriaceous particles suggest that they are formed from matrix materials that are enriched in volatiles. The volatile components such as water, sulfide, Na, K, etc. have vanished due to partial evaporation and degassing during Earth's atmospheric entry leaving behind the vesicular features, yet largely preserving the elemental composition. The elemental ratios (Ca/Si, Mg/Si, Al/Si, Fe/Si, and Ni/Si) of interplanetary dust particles (IDPs) are compatible with the scoriaceous CSs, which in turn are indistinguishable from the matrices of CI and CM chondrites signifying similarities in the nature of the sources. Furthermore, the texture of cometary particles bears resemblance to the texture of the scoriaceous particles. The compilation of petrographic texture, chemical, and trace element composition of scoriaceous CSs presents a strong case for matrix components from hydrated and volatile-rich bodies, such as CI and CM chondrites, rather than chondrules. We conclude that the fine-grained scoriaceous CSs, the matrix materials of hydrated chondrites, IDPs, and cometary particles that overlap compositionally were widespread, indicating a dominant component in the early solar nebula.     

Oxygen isotopic and chemical composition of chromites in micrometeorites: Evidence of ordinary chondrite precursors

We identified 66 chromite grains from 42 of ~5000 micrometeorites collected from Indian Ocean deep‐sea sediments and the South Pole water well. To determine the chromite grains precursors and their contribution to the micrometeorite flux, we combined quantitative electron microprobe analyses and oxygen isotopic analyses by high‐resolution secondary ion mass spectrometry. Micrometeorite chromite grains show variable O isotopic compositions with δ¹⁸O values ranging from ?0.8 to 6.0‰, δ¹⁷O values from 0.3 to 3.6‰, and Δ¹⁷O values from ?0.9 to 1.6‰, most of them being similar to those of chromites from ordinary chondrites. The oxygen isotopic compositions of olivine, considered as a proxy of chromite in chromite‐bearing micrometeorites where chromite is too small to be measured in ion microprobe have Δ¹⁷O values suggesting a principal relationship to ordinary chondrites with some having carbonaceous chondrite precursors. Furthermore, the chemical compositions of chromites in micrometeorites are close to those reported for ordinary chondrite chromites, but some contribution from carbonaceous chondrites cannot be ruled out. Consequently, carbonaceous chondrites cannot be a major contributor of chromite‐bearing micrometeorites. Based on their oxygen isotopic and elemental compositions, we thus conclude with no ambiguity that chromite‐bearing micrometeorites are largely related to fragments of ordinary chondrites with a small fraction from carbonaceous chondrites, unlike other micrometeorites deriving largely from carbonaceous chondrites.     

Non-sinusoidal transit timing variations for the exoplanet HAT-P-12b

Considering the importance of investigating the transit timing variations(TTVs) of transiting exoplanets,we present a follow-up study of HAT-P-12 b.We include six new light curves observed between2011 and 2015 from three different observatories,in association with 25 light curves taken from the published literature.The sample of the data used thus covers a time span of ～10.2 years with a large coverage of epochs(1160) for the transiting events of the exoplanet HAT-P-12 b.The light curves are utilized to determine the orbital parameters and conduct an investigation of possible TTVs.The new linear ephemeris shows a large value of reduced χ~2,i.e.X~2_(red)(23)=7.93,and the sinusoidal fitting using the prominent frequency coming from a periodogram shows a reduced χ~2 around 4.Based on these values and the corresponding O-C diagrams,we suspect the presence of a possible non-sinusoidal TTV in this planetary system.Finally,we find that a scenario with an additional non-transiting exoplanet could explain this TTV with an even smaller reduced χ~2 value of around 2.