The Fe-Line Feature in the X-Ray Spectrum of Solar Flares: First Results from the SOXS Mission

We present the first results from the low-energy detector payload of the solar X-ray spectrometer (SOXS) mission, which was launched onboard the GSAT-2 Indian spacecraft on May 08, 2003 by the GSLV-D2 rocket to study solar flares. The SOXS low-energy detector (SLD) payload was designed, developed, and fabricated by the Physical Research Laboratory (PRL) in collaboration with the Space Application Centre (SAC), Ahmedabad and the Indian Space Research Organization (ISRO) Satellite Centre (ISAC), Bangalore. The SLD payload employs state-of-the-art, solid-state detectors, viz., Si PIN and Cadmium-Zinc-Telluride (CZT) devices that operate at near room temperature (−20 ^°C). The energy ranges of the Si PIN and CZT detectors are 4 – 25 and 4 – 56 keV, respectively. The Si PIN provides sub-keV energy resolution, while the CZT provides ~1.7 keV energy resolution throughout the energy range. The high sensitivity and sub-keV energy resolution of the Si PIN detector allows measuring the intensity, peak energy, and the equivalent width of the Fe-line complex at approximately 6.7 keV, as a function of time in all ten M-class flares studied in this investigation. The peak energy (E _p) of the Fe-line feature varies between 6.4 and 6.7 keV with increase in temperature from 9 to 58 MK. We found that the equivalent width (w) of the Fe-line feature increases exponentially with temperature up to 30 MK and then increases very slowly up to 40 MK. It remains between 3.5 and 4 keV in the temperature range of 30 – 45 MK. We compare our measurements of w with calculations made earlier by various investigators and propose that these measurements may improve theoretical models. We interpret the variation of both E _p and w with temperature as being to the changes in the ionization and recombination conditions in the plasma during the flare, and as a consequence, the contribution from different ionic emission lines also varies.     

Data acquisition, control, communication and computation system of solar X-ray spectrometer (SOXS) mission

The Solar X-ray Spectrometer (SOXS) mission onboard GSAT-2 Indian Spacecraft was launched on 08 May 2003 using GSLV-D2 rocket by Indian Space Research Organization (ISRO). SOXS aims to study solar flares, which are the most violent and energetic phenomena in the solar system, in the energy range of 4–56 keV with high spectral and temporal resolution. SOXS employs state-of-the-art semiconductor devices, viz., Si-Pin and CZT detectors to achieve sub-keV energy resolution requirements. In this paper, we present an overview of data acquisition, control, communication and computation of low energy payload of the SOXS mission.     

Hydrometeorological processes in semi-arid western India: insights from long term isotope record of daily precipitation

Long term (2005–2016) daily precipitation isotope data (δ18O, δD and d-excess) from Ahmedabad in semi-arid Western India are examined in light of various meteorological parameters and air parcel trajectories to identify prominent patterns in the isotopic character and discern the underlying hydrometeorological processes. One of the most prominent and systematic annual patterns is the isotopic depletion (average δ18O: − 2.5‰ in Jun–Jul; − 5.2‰ in Aug–Sept) in the second half of the Indian Summer Monsoon (ISM), which is observed in the 11 out of the 12 years of this study. Four geographically feasible causal factors have been examined if they contribute to observed late monsoon isotopic depletion. These factors are: (1) increased contribution of terrestrially recycled vapor; (2) intra-seasonal change in sea-surface, surface-air and cloud base temperatures; (3) increased rain-out fraction from marine vapor parcel; and (4) increase in relative proportion of convective rain. It is inferred from the present study that isotopic depletion in the second half of ISM is associated with: (1) increased contribution (45% from 36%) of terrestrially recycled moisture; (2) 1.9° C lower cloud base temperature; (3) increased rainout fraction due to decreased wind velocity (6.9 m/s from 8.8 m/s); and (4) an increase of 22.3% in the proportion of convective rain. Daily rain events with atypical isotopic composition (20‰ < d-excess < 0‰) are ascribed mainly to local weather perturbations causing sudden updraft of moist air facilitating terrestrial recycling of water vapor.     

Simulation of monsoon intraseasonal variability in NCEP CFSv2 and its role on systematic bias

We have evaluated the simulation of Indian summer monsoon and its intraseasonal oscillations in the National Centers for Environmental Prediction climate forecast system model version 2 (CFSv2). The dry bias over the Indian landmass in the mean monsoon rainfall is one of the major concerns. In spite of this dry bias, CFSv2 shows a reasonable northward propagation of convection at intraseasonal (30–60 day) time scale. In order to document and understand this dry bias over the Indian landmass in CFSv2 simulations, a two pronged investigation is carried out on the two major facets of Indian summer monsoon: one, the air–sea interactions and two, the large scale vertical heating structure in the model. Our analysis shows a possible bias in the co-evolution of convection and sea surface temperature in CFSv2 over the equatorial Indian Ocean. It is also found that the simulated large scale vertical heat source (Q1) and moisture sink (Q2) over the Indian region are biased relative to observational estimates. Finally, this study provides a possible explanation for the dry precipitation bias over the Indian landmass in the simulated mean monsoon on the basis of the biases associated with the simulated ocean–atmospheric processes and the vertical heating structure. This study also throws some light on the puzzle of CFSv2 exhibiting a reasonable northward propagation at the intraseasonal time scale (30–60 day) despite a drier monsoon over the Indian land mass.     

Groundwater socio-ecology and governance: a review of institutions and policies in selected countries

Groundwater is crucial for the livelihoods and food security of millions of people, and yet, knowledge formation in the field of groundwater has remained asymmetrical. While, scientific knowledge in the discipline (hydrology and hydrogeology) has advanced remarkably, relatively little is known about the socio-economic impacts and institutions that govern groundwater use. This paper therefore has two objectives. The first is to provide a balanced view of the plus and the down side of groundwater use, especially in agriculture. In doing so, examples are drawn from countries such as India, Pakistan, Bangladesh, China, Spain and Mexico—all of which make very intensive use of groundwater. Second, institutions and policies that influence groundwater use are analyzed in order to understand how groundwater is governed in these countries and whether successful models of governance could be replicated elsewhere. Finally, the authors argue that there is a need for a paradigm shift in the way groundwater is presently perceived and managed—from management to governance mode. In this attempt, a number of instruments such as direct regulation, indirect policy levers, livelihood adaptation and peoples participation will have to be deployed simultaneously in a quest for better governance.

Spectral Characteristics of Some Horticultural and Vegetable Crops at Different Growth Stages

Ground based remote sensing experiments using multispectral radiometer were condueted during December 1992 to March 1993, at horticultural field of Mahatma Phule Krishi Vidyapeeth, located in Pune, over banana, grapes, brinjal and tomato crops for studying the spectral response at different growth stages and vigour. The spectral characteristics and the various vegetative indices of diseased and healthy plants are discussed in this paper. Besides its significance in ground based remote sensing, these studies may be helpful for decision making in the area of condition assessment of crops through satellite remote sensing, as the spectral bands of the radiometer used in this experiment are similar to those of IRS and Landsat satellites. Moreover, the growth profiles of brinjal and banana crops can be useful in the area of crop and vegetable discrimination.     

Frequency dependence of equatorial ionospheric scintillations

Simultaneous observations of amplitude scintillations at 40 MHz, 140 MHz and 360 MHz radiated from ATS-6 satellite at 34° E longitude were made at Ootacamund near the magnetic equator in India. It has been found that the frequency variation of scintillation index (S ₄) isS ₄ ∞f ^?n , withn being about 1·2 only for weak scintillations, i.e., so long as the scintillation index does not exceed 0·6 at the lower frequency. For strong scintillations (S ₄>0·6) where multiple scattering may be present, the exponentn itself is a function of the intensity of scintillation, the scintillation indices at two frequencies are related by:S ₄(f ₁)=S ₄(f ₂) exp [1·3 log(f ₂/f ₁)(1?S ₄(f ₂)] so long asf ₂/f ₁≤3. Thus knowing scintillation index at a given frequency one can estimate the scintillation index at another frequency. This will be of significant importance for communication problems. Evidence is also shown for the reversal of the frequency law in cases of intense scintillations.