Ca X line ratios in solar flares

Theoretical Ca X electron temperature sensitive emission line ratios, derived using electron excitation rates interpolated from accurateR-matrix calculations, are presented forR ₁ =I(419.74 )/I(574.02 ,),R ₂ =I(411.65 )/I(574.02 ),R ₃ =I(419.74 )/I(557.75 ), andR ₄ =I(411.65 )/I(557.75 ). A comparison of these with observational data for three solar flares, obtained by the Naval Research Laboratory's S082A slitless spectrograph on boardSkylab, reveals good agreement between theory and observation forR ₁ andR ₃ in one event, which provides limited support for the accuracy of the atomic data adopted in the analysis. However, in the other flares the observed values ofR ₁ –R ₄ are much larger than the theoretical high-temperature limits, which is probably due to blending of the 419.74 line with Civ 419.71 , and 411.65 with possibly Ciii 411.70 .     

Numerical simulation of physical and dynamical characteristics associated with the severe thunderstorm on April 5, 2015 at Kushtia and Jhenaidah

The paper deals with the study of the physical and dynamical characteristics of a severe thunderstorm, which had occurred on April 5, 2015, at about 2100 UTC in the southwestern Bangladesh with location around 23.3–23.7N and 89.0–89.4E within the upazilas (sub-districts) of Kumarkhali and Shailkupa under the districts of Kushtia and Jhenaidah, respectively. The thunderstorm was associated with numerous hails of large size. More than 5000 birds which used to live in the bird sanctuary at Shailkupa and 22,011 birds in Chhaglapara Bird Sanctuary of Kumarkhali died as they were hit by the hails. Large hails also damaged crops, houses and forests over the thunderstorm hit areas. The evolution of the thunderstorm is studied by the WRF model, which is initialized using the National Centers for Environmental Prediction Final reanalysis data of 0000 UTC of April 5, 2015. The simulated results provide a basis to study the physical and dynamical characteristics of the thunderstorm, which are generally not identified by the meteorological observations which are too sparse. The model has captured a micro-low over Kumarkhali and its neighborhood, which favored the occurrence of the severe thunderstorm. The model simulated rainfall is about 26 mm near the place of occurrence, which matches well with the area where the reflectivity of hydrometeor is maximum. The convective available potential energy is found to be 1600 J kg^?1 at 1730 UTC near the place of occurrence of the thunderstorm; this indicates high atmospheric instability over the thunderstorm location for the formation of the thunderstorm. The vertical velocity, convergence, cloud water mixing ratio and the ice water mixing ratio and their vertical extensions are found to be satisfactory and responsible for the occurrence of large hails associated with the thunderstorm.     

An improved lunar moment of inertia determination: a proposed strategy

The current error of 0.0025 on the lunar homogeneity parameterI/MR ² is dominated by the uncertainties in theC ₂₀ andC ₂₂ gravity harmonics. This error level is equivalent to a 4.20 gm cm^–3 density uncertainty for a lunar interior model having a core 300 km in radius. Covariance analyses are performed using Doppler data from the relay satellite of the proposed Lunar Polar Orbiter mission to determine an optimum reduction strategy which obtains an order of magnitude improvement in the gravity estimates. Error studies show the long-arc reduction method obtains results which are an order of magnitude more accurate than the short-arc technique. The nominal 4000 km circular orbit of the relay satellite is very sensitive to the unmodeled effects of gravity harmonics of degree 5 through 9. Results from this orbital geometry indicate that it may not be possible to achieve the desired order of magnitude accuracy improvement. A modified orbit having the identical orbital conditions as the nominal one, but with a larger semi-major axis of 7000 km is studied. Results show the desired order of magnitude improvement can be achieved when a complete fourth degree and order model and some fifth and sixth degree terms are estimated while considering the unmodeled effects of the remaining harmonics through degree and order eight. Studies also show a 50% additional improvement inC ₂₂ can be achieved if differential differenced Doppler is also processed with the direct Doppler. The improved uncertainty inI/MR ² reduces the core density error from 4.20 gm cm^–3 to 0.1 gm cm^–3 for the case of a lunar density model having a 300 km core radius.Contribution #2885 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.     

Line diagnostics for Ne V and Mg V solar ions

Spectroscopic diagnostics for the Nev and Mgv solar ions have been investigated. The theoretical forbidden line ratios from these ions are presented for estimating the Ne/Mg variation in different solar structures. Calculations for density and temperature line diagnostics of these ions are given for the several spectral line ratios and their applications are discussed with the help of available solar observations in space. Future observations from the CDS and the SUMER experiments aboard the SOHO satellite are also discussed.     

Critical evaluation and geological correlation of teleseismic phase data from Indian seismological stations

We evaluated the quality of seismic phase data from Indian seismological stations through the analysis of teleseismic travel times reported during 1976–83 and infer that only WWSSN stations (NDI, SHL, POO, KOD) apart from GBA and HYB can be rated satisfactory while the majority of stations (more than 40) produce very poor quality data sets. Detailed analysis of teleseismic P-wave travel time residuals shows that while the average structure of the upper mantle beneath India has high velocity (negative residuals) there are marked lateral variations. In particular, three zones of anomalous positive residuals (low velocity) are observed: one beneath the north western part of the Deccan trap, the second covering the southernmost peninsula (granulite terrain) and a third rather localized one, to the north of Delhi coinciding with Delhi-Haridwar ridge. New Delhi exhibits strong negative residuals in the E-SE quadrant along with negative station anomaly, implying that it is underlain by an anomalous high velocity crust/upper mantle. The negative residuals observed over India, continue beneath the Himalaya till the south of Lhasa but change sign further northward, suggesting the northern limit of the Indian upper mantle structure.     

Use of the Hilbert transform to interpret self-potential anomalies due to two-dimensional inclined sheets

Self-potential anomalies due to two-dimensional inclined sheet of finite depth extent are analysed from their horizontal and vertical derivatives via the Hilbert transform. The depths to the top and bottom of the sheet and the inclination are obtained by means of simple mathematical expressions. The method is applied to a theoretical example and to a field S.P. anomaly over a sulphide deposit in the Kalava fault zone of Cuddapah basin, India. The presence of random noise is analysed for various levels and its effect is discussed. This interpretation process can be automated for all practical purposes by simple programming.     

Living planktonic foraminifera during the late summer monsoon period in the Arabian Sea

During the late summer monsoon living planktonic foraminifera were collected in the southeastern Arabian Sea between 3°N and 15°N by using six vertical plankton tows. Sixteen species of planktonic foraminifera were identified. Among them, Globigerinoides ruber and Globigerinoides sacculifer are the most abundant species, while the ecologically most important species Globigerina bulloides is very rare. The low abundance of G. bulloides can be explained by the warming of the surface water in combination with deepening of the mixed layer, since this species preferentially dwells in nutrient-rich upwelling waters. The population density of planktonic foraminifera ranges between 31 and 185 specimens per 10⁻³ m³. The low absolute numbers of planktonic foraminifera are similar to the numbers which were reported before from the non-upwelling areas in the Arabian Sea. The low absolute numbers and the collected foraminiferal assemblages are therefore highly indicative of the Arabian Sea non-upwelling areas. Particularly significant are the low absolute and relative numbers of the non-spinose species Globorotalia menardii and Neogloboquadrina dutertrei. The absence of these species indicate the relatively low nutrient levels in this area at the tail end of the summer monsoon period.     

Equilibrium structure of differentially rotating polytropic models of the stars

In this paper we propose a method for computing the equilibrium structure of differentially rotating polytropic models of the stars. A general law of differential rotation of the type ²=b ₀+b ₁ s ²+b ₂ s ⁴, which can account for a reasonably large variety of possible differential rotations in the stars has been used. The distortional effects have been incorporated in the structure equations up to second order of smallness in distortion parametersb ₀,b ₁, andb ₂ using Kippenhahn and Thomas' averaging approach in conjunction with Kopal's results on Roche equipotentials in manner similar to the one earlier used by Mohan and Saxena for computing the equilibrium structure of polytropes having solid body rotation. Numerical results have been obtained for various types of differentially rotating polytropic models of stars of polytropic indices 1.5, 3, and 4. Certain differentially rotating models of the Sun which are possible with such a type of law of differential rotation, have also been computed.