Calcium boro fluoro zinc phosphate glasses modified using alkali oxide and doped with Nd3+ and Er3+ ions with the chemical composition of 69.5 (B2O3) + 10 (P2O5) + 10 (CaF2) + 5 (ZnO) + 5 (Na2O/Li2O/K2O) + 0.5 (Er2O3/Nd2O3) were prepared using a conventional melt quenching technique. The results of X-ray diffraction patterns indicated the amorphous nature of all the prepared glasses. The visible-near-infrared red (NIR) absorption spectra of these glasses were analyzed systematically. The NIR emission spectra of Er3+ and Nd3+:calcium boro fluoro zinc phosphate glasses showed prominent emission bands at 1536 nm (I-4(13/2)-> I-4(15/2)) and 1069 nm (F-4(3/2)-> I-4(11/2)) respectively with lambda(exci) = 514.5 nm (Ar+ laser) as the excitation source.

Using advanced meteor radar network observations along with ERA5 data, we report observational evidence of polar to tropical mesospheric teleconnections during the 2018 major sudden stratosphere warming (SSW) event in the northern hemisphere.A peak SSW on February 14, 2018, characterized by a ˜45 K rise in polar stratosphere temperature and a zonal wind reversal of ˜(-25) m/s at 60°N and 10 hPa, is observed.In the tropical lower mesosphere, a maximum zonal wind reversal (-24 m/s) compared with that identified in the extra-tropical regions was observed.Moreover, a time delay in the wind reversal between the tropical/polar stations and the mid-latitudes was detected.The wind reversal in the mesosphere is due to the propagation of dominant intra-seasonal oscillations (ISOs) of 30-60-days and the presence and superposition of 8-day period planetary waves (PWs).The ISOs phase propagation is observed from the high-to low-latitudes (60 °N to 20 °N) in contrast to 8-day PWs phase propagation, indicating the change in the meridional propagation of winds during SSW.However, the superposition of dominant ISOs and weak 8-day PWs could be responsible for the delay of the wind reversal in the tropical mesosphere.Therefore, this study has strong implications for understanding the reversed (polar to tropical) mesospheric meridional circulation during SSW. Hosted fileessoar.10510284.1.docx

Processes behind Sudden Stratospheric Warming (SSW), which occurs more frequently in the northern hemispheric polar latitudes and its influence from the stratosphere to the upper atmosphere are well documented. However, physical processes associated with SSW, although it ensues rarely in the southern hemisphere (SH), have a strong influence on the background atmosphere from the stratosphere to the mesosphere and are poorly understood. Using a ground-based meteor radar, satellite-borne Microwave-Limb sounder, and Modern-Era Retrospective Analysis for Research and Applications observations, we identified cooling of Antarctic mesopause by 26 K in response to a 66 K warming in the polar stratosphere during the 2019 minor SSW in the SH. The observed cooling is attributed to the interplay between planetary waves, CO2 infrared cooling, and O3 depletion, rather than adiabatic cooling due to gravity waves alone during SSW. It is proposed that anthropogenic and other sources generating chemical tracers in the lower atmosphere have caused mesospheric cooling and could be transported from the lower atmosphere both vertically and meridionally through residual mean meridional circulation from the tropics. Therefore, our study for the first time demonstrates the effect of lower atmosphere chemistry on the polar mesosphere thermal structure during the 2019 SSW.

The signature of the low-latitude mesosphere response to the February 2017 minor sudden stratosphere warming (SSW) was detected using the observations of a meteor radar at Fuke (19.5°N, 109.1°E) a low-latitude station in China and ERA-5 data. Radar detected the zonal wind reversal in the mesosphere three days before the SSW event, whereas the ERA-5 does not reproduce the mesospheric wind response at low-latitudes during the 2017 SSW and large discrepancies are found between the mesospheric zonal winds derived from the Fuke radar and ERA-5. The quasi oscillatory pattern was noted in the meridional winds before the SSW event, afterward, the northward winds are significant. We observed the existence of 20–28-day planetary waves (PWs) in the Fuke meteor radar measured mesospheric zonal winds before the SSW and the 2-12-days period PWs before and after the SSW in the meridional winds. The zonal structure and periodicity of the PWs have been verified with the other meteor radar at the Indian tropical station Tirupati (13.63°N, 79.4°E). However, ERA-5 does not capture the PW activity in the mesosphere as radar. The similarities and dissimilarities among the different techniques have been discussed. Therefore, the present study re-emphasizes the strong response of the low-latitude mesosphere to the 2017 minor SSW in a manner similar to the major SSW event.

The observations of the advanced meteor radar at the Indian tropical station Tirupati (13.63 degrees N, 79.4 degrees E) have been used to investigate the effects of the 2017 minor Sudden Stratospheric Warming (SSW) on the tropical mesosphere and lower thermosphere (MLT). The episodic minor warmings were observed in February 2017 with the gain of similar to 40 K in the polar stratospheric temperature (PST), followed by a weakening of the eastward wind by 27 m/s. The observations show the large temporal variations in the zonal wind at 75-80 km during the SSW. We report the occurrence of 14-16 day waves in the MLT zonal wind during SSW and the secondary waves (2-7 days) in the meridional wind after SSW. A large enhancement (similar to 30 m/s) is observed in the amplitude of the semi-diurnal tide (SDT) during the SSW. The present results are similar to those observed during the major SSW. Therefore, the present results stress that the studies of minor SSW on the tropical MLT dynamics must be important. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.

Objective: It is theoretically observed that atmospheric gravity waves play a key role in vertical coupling during the Mesosphere Temperature Inversion (MTI). Therefore, the present paper describes the observational evidence for vertical coupling between the stratosphere and mesosphere through the short-period gravity waves (GWs), during the Mesosphere Temperature Inversion (MTI) over a tropical region, Gadanki (13.5oN, 79.2oE), India. Method: The combined observations of Mesosphere-Stratosphere-Troposphere (MST) Radar and Rayleigh LIDAR located at Gadanki is utilized to study the vertical coupling. We used a unique experimental design from the two ground-based instruments that scan the lower and middle atmosphere simultaneously during the observational campaign. This kind of combined instruments are very sparsely located on the same site to make the observations unique to understand the vertical coupling processes of GWs. Result: The vertical flux of the horizontal momentum of GWs of periods in the range 20 min. to 2h is investigated in the mesosphere using the MST Radar winds. The emphasis is made on the variability of zonal and meridional momentum fluxes in the mesosphere and possible reasons for the variability of fluxes during MTI. It is observed that raise in momentum fluxes of ~7 m2/ s2 in the eastward flux and ~10 m2/s2 in southward flux at mesospheric altitudes during the MTI. Conclusion: The gravity wave (GW) analysis using the LIDAR temperature profiles indicate the connection between GW breaking at mesosphere altitudes and temperature inversion and thus the turbulence caused mesospheric echoes. The study suggests the prospect of coupling between stratosphere and mesosphere during the MTI.

Objective: Usually, the stratospheric ozone will show its significance in the variability of mesospheric tides in normal days over the low-latitude region.But during sudden stratosphere warmings, the water vapor and ozone over the polar region will change and shows some different effects on mesosphere tides.In the present study, we have provided the unusual changes in both water vapor and ozone over Antarctica and their role in altering the mesospheric tides.Method: Using MLS data in the stratosphere and Rothera (68oS, 68oW) MF radar observations in the mesosphere, the variability of Antarctica ozone and H2O during sudden stratospheric warming (SSW) winter 2010, and their influence on mesosphere dynamics has presented.The unusual increment of ozone reduction is noticed and consequent enhancement in H2O and HNO3 is also observed during the warming period.Mesospheric tidal components (diurnal, semi-diurnal and terr-diurnal) have been estimated using the hourly wind data from the MF radar. Result:The unusual changes in H2O and Ozone were observed during the warming period the similar behavior was observed in semi-diurnal tidal components during 2010 winter and their relation to ozone enhancement is discussed. Conclusion:The observations indicate that the enhancement of H2O and HNO3 leads to produce the ozone during warming period and hence the increment in ozone reduction is achieved over the polar region.Further, the enhancement of Brewer-Dobson mean circulation was clearly noticed through ozone transport during the warming period.The tidal enhancement after the SSW could be due to the non-linear interaction between planetary waves and tides.

We have utilized the Gadanki MST Radar and Rayleigh LIDAR to understand the vertical coupling between the lower atmosphere and mesosphere through the short-period gravity waves (GWs). The short-period GWs (20 min-2 h) are noticed both in the troposphere and in the mesosphere during the deep convection. During the convection, the large vertical velocities (>5 m/s) and significant variations in the momentum flux (similar to 3 m(2)/s(2)) are noticed in the troposphere and higher fluxes (similar to 45 m2=s2) are evidenced in the mesosphere. The observations suggest the vertical coupling between the lower and middle atmosphere during convection.

In the present study pure and Fe (5% and 10 %) doped CdSe nanoparticles were prepared by chemical co-precipitation method. XRD diffraction patterns show that the diffracted peaks are well matched with the standard powder diffraction data and had a hexagonal structure. The average crystallite size of Fe doped CdSe nanoparticles estimated from Scherrer formula decreases from 18 to 12 nm with the increase of Fe concentration from 5 to 10%. The optical band gap of Fe doped CdSe nanoparticles increases from 1.88 to 2.20 eV with the increase of Fe doping concentration which can be attributed to decrease in particle size and due to quantum confinement. The prepared samples were also characterized with DSC and FTIR analysis.

In the present work, pure CdS and Ni doped CdS nanoparticles have been synthesized by chemical co-precipitation method using thiophenol as a capping agent. The frequency dependent dielectric dispersion of pure CdS and Ni doped CdS nanoparticles are investigated at room temperature in the frequency range of 100 Hz - 1 MHz by impedance spectroscopy. The dielectric properties and ac conductivity (sigma(ac)) of the samples were measured as a function of frequency. The plots of Z' vs Z '' (Z' is the real part of impedance and Z '' is the imaginary part) for Ni doped CdS were recorded at room temperature over the frequency ranges. All samples have a semicircle arc originating at the origin point. This indicates that each composition can be described by one bulk resistance and one bulk capacitance both connected parallel. The centre below the real axis indicates the relaxation behaviour of the system.

In the present work, conventional chemical co-precipitation method was employed for the prepation of Nickel (2,4,6,8& 10 at % of Ni) doped CdS nanoparticles. The particle size and lattice parameters for each sample are determined from X-ray diffraction (XRD) analysis. From XRD patterns the broadening of the diffraction peaks indicates the nanostructure nature of the samples. Surface morphology of the samples was studied by Scanning Electron Microscope (SEM). Compositional Elemental analysis of data is obtained from

In the Present work, conventional chemical co-precipitation method was employed for the preparation of Nickel (2, 4, 6, 8 and 10 at % of Ni) doped CdS nanoparticles. The particle size and lattice parameters for each sample are determined from X-ray diffraction (XRD) analysis. From XRD patterns the broadening of the diffraction peaks indicates the nanostructure nature of the samples. Surface morphology of the samples was studied by Scanning Electron Microscope (SEM). Compositional Elemental analysis of data is obtained from Energy Dispersive Analysis of X-ray (EDAX) plots.

In the present investigation, conventional chemical co-precipitation method was used for the preparation of Nickel (2, 4, 6, 8 & 10 at% of Ni) doped CdS nanoparticles. The UV/Vis absorption spectrum and Photoluminescence spectra (PL) were recorded for studying the optical properties of Ni doped CdS nanoparticles. The band gap energy of the Nickel doped CdS samples corresponding to absorption edge are found in the range of 3.14eV-3.54eV. The increase in band gap with the decrease of size of the particles is due to quantum confinement which modulates the band structure of nanoparticles in semiconductors.