This study presents the analysis of planetary waves (PWs) using daily mean wind velocities for four years (August 2013 to July 2017) of continuous measurements using MF radar over the low latitude Indian region Kolhapur (16.8 degrees N; 74.2 degrees E). The MF radar at Kol-hapur was upgraded in 2013. These are the first results of PWs after the upgradation of MF radar. The seasonal and intra-seasonal vari-abilities of East-West (EW) traveling PWs in the MLT region have been studied. In the present work, the data was analyzed to study the waves with various periodicities (e.g. 3-4, 5-8, 15-17, and 30-60 days). The 3.5 day [Ultra-Fast Kelvin (UFK)] wave shows semiannual variability with burst like wave activity observed during the summer months and December solstice. In addition, it is observed to be stronger in the spring equinoctial period. A strong semiannual oscillation (SAO) has been observed in a 6.5-day wave with peaks near the equinoxes. Similar to SAO over the low latitude MLT region, the wave activity is stronger in April/May than in September/October. The 6.5-day waves are observed to be stronger when the background mean wind is westward. From the analysis, it has been seen that the period before and after the equinoctial period is favorable for the 6.5-day wave propagation. The 16-day wave has no significant seasonal dependence; instead, the waves spread to almost all seasons. The Madden-Julian Oscillations (MJOs) have been observed to be propa-gating with an average wind speed of 5 m/s when the background mean wind is eastward. The occurrence of MJO is observed during the summer and winter months. These results are the first of their kind in two aspects: first, they show the PWs with enhanced altitude coverage covering up to 110 km, and second, they show the PWs not contaminated due to equatorial electro jet influence. (c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies.

This study presents the quasi-two-day wave (Q2DW) characteristics of the mesosphere and lower thermosphere (MLT) region obtained by taking hourly mean values of horizontal wind velocities for 4 years (August 2013 July 2017) through continuous measurements using a medium-frequency (MF) radar (operating frequency - 1.98 MHz) located at the low-latitude Indian station Kolhapur (16.8 degrees N; 74.2 degrees E). The MF radar located at Kolhapur was upgraded in 2013, and these results of Q2DW have been reported for the first time after upgrading. The present study investigated variability in seasonal, annual, interannual, and solar indices of Q2DWs traveling in zonal (EW) and meridional (NS) components in the MLT region. The Q2DW activity is observed to be stronger during austral summer (January-February) (EW = similar to 5 m/s and NS = similar to 8-10 m/s) than during boreal summer (June-July) (EW = similar to 5 m/s and NS = similar to 6-8 m/s). The Q2DW amplitudes are larger in the meridional component than in the zonal one. A strong semiannual oscillation (SAO) has been observed in Q2DWs, with peak during January-February and June-July. In addition, small enhancement is seen in meridional Q2DW in October (similar to 5-6 m/s). It is observed that the entire spectrum (40-60 h) measured between 86 and 94 km contributes to the SAO amplitudes during January-February and June-July, whereas the waves measured between 42 h and 52 h contribute to enhancement in October similar to that reported elsewhere. In general, the Q2DW amplitude shows large interannual variability. The easterlies developed in the global circulation model in Northern hemisphere during May intensify up to around summer solstice. Q2DW activity peaks during westerly shear zone and intensifies with time at a lower thermospheric altitude (above 90 km). Small positive correlations (r = 0.2 for sunspot number and r = 0.1 for 10.7 cm solar flux) have been observed between Q2DW amplitudes and solar activity. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.

The nightglow observations of OI 630.0 nm emission carried out from low latitude station Kolhapur using All Sky Imager (ASI) with \(140^{\circ}\) field of view (FOV) for the month of April 2011 are used. The images were processed to study the field aligned irregularities often called as equatorial plasma bubbles (EPBs). The present study focuses on the occurrence of scintillation during the traversal of EPBs over ionospheric pierce point (IPP). Here we dealt with the depletion level (depth) of the EPB structures and its effect on VHF signals. We compared VHF scintillation data with airglow intensities at Ionospheric pierce point (IPP) from the same location and found that the largely depleted EPBs make stronger scintillation. From previous literature, it is believed that the small scale structures are present near the steeper walls of EPBs which often degrades the communication, the analysis presented in this paper confirms this belief.

Medium Frequency (MF) radar located at Kolhapur (16.8 degrees N, 74.2 degrees E) has been upgraded in August 2013. Since then continuous measurements of zonal and meridional winds are obtained covering larger altitudes from the Mesosphere and Lower Thermosphere (MLT) region. Diurnal, monthly and seasonal variation of these mean winds is presented in this study using four years (2013-2017) of observations. The percentage occurrence of radar echoes show maximum between 80 and 105 km. The mean meridional wind shows Annual Oscillation (AO) between 80 and 90 km altitudes with pole-ward motion during December solstice and equatorial motion during June solstice. Quasi-biennial oscillation (QBO) with weaker amplitudes are also observed between 90 and 104 km. Zonal winds show semi-annual oscillation (SAO) with westward winds during equinoxes and eastward winds during solstices between 80 and 90 km. AO with eastward winds during December solstice and westward wind in the June solstice is also observed in the mean zonal wind between 100 and 110 km. These results match well with that reported from other latitudes within Indian region between 80 and 90 km. However, above 90 km the results presented here provide true mean background winds for the first time over Indian low latitude region as the present station is away from equatorial electro-jet and are not contaminated by ionospheric processes. Further, the results presented earlier with an old version of this radar are found contaminated due to unknown reasons and are corrected in the present work. This upgraded MF radar together with other MLT radars in the Indian region forms unique network to investigate the vertical and lateral coupling.

Total column ozone (TCO) distribution and its variation over the Indian region at different stations for the period of about 30 years from 1986 to 2015 are studied. TCO data is taken from the merged ozone data set (MOD) overpass data for 15 different stations over India. The average correlation between TCO and solar proxies such as sunspot number and F10.7 cm solar flux is more than 0.5. We further divided the time series of TCO according to solar cycle as 22nd solar cycle (September 1986 to July 1996), 23rd solar cycle (August 1996 to November 2008) and 24th solar cycle (December 2008 to December 2015) (on going cycle) for a period of 1986-2015. Herein, for the long term trend analysis of TCO, we have removed the seasonal effect by the deseasonalization process, the effects of solar activities, stratospheric waves (quasi-biennial-oscillation-QSO and El Nino-Southern Oscillation-ENSO) by the multifunction linear regression method (MLR). We have compared both the linear trends in TCO which are calculated by the simple linear regression (SLR) and deseasonalised multifunction linear regression (DMLR) analysis. It is found that the direction of the trend in 22nd and the 23rd solar cycle is similar while, it is opposite in the 24th solar cycle. We observed a more negative trend in the 22nd solar cycle and less negative trend in the 23rd solar cycle while the trend is positive in the 24th solar cycle. The results indicate that after the DMLR process, the trend values are decreased by a large factor. Therefore, it is found that the role of natural variability is more than that of the ozone depleting substances (ODS) on long term variability in TCO over India. This statistical analysis provides better analysis of trend variation in TCO series over India. The main objective of this work is to analyze the variations in trend in the TCO with respect to the recent three solar cycles.

This paper reports the statistical analysis of zonal drift velocity of equatorial plasma bubbles (EPBs) inferred from advanced optical technique (all‐sky imager) with OI 630.0‐nm airglow emission from January to April of 2011 to 2013. Over 143 nights of observations have been carried out using all‐sky imager over low‐latitude station Kolhapur (16.8°N, 74.2°E; 10.6°N dip latitude), out of which 58 nights showed signatures of EPBs. We study the hourly, monthly, and seasonal variation in zonal drift velocity of EPBs. Also, the magnetically disturbed nights (Ap > 18) are separately studied. It is observed that (a) the daily peak zonal drift velocity is seen to be positively correlated to corresponding daily averaged 10.7‐cm solar flux. (b) The zonal drift velocity is found to be larger in the equinox months than that of winter months. (c) During the disturbed nights the zonal drift velocity gets slower and one of the disturbed nights showed the latitudinal variation in zonal drift velocity during the development phase of EPBs before midnight hours. We suggest that this variation might be occurred due to the disturbance dynamo electric fields at low latitude, which reduces the EPBs' eastward velocity. (d) The zonal drift velocity of EPBs presented in this paper is in good agreement with the previous studies as well as the HWM‐07 model values.

The amplitude scintillation data, recorded at 251 MHz by two spaced receivers at low latitude station Kolhapur [16.42oN, 74.2oE] are used. We have considered data of magnetically disturbed days (Ap > 20) to investigate the effect of magnetic activity on the ionospheric irregularities by observing the coherence scales of the scintillation pattern produced by the irregularities. The coherence scales are calculated using the method introduced by Bhattacharyya et al. (2003). Coherence scale lengths on magnetically disturbed days are higher than that of on quiet days. During magnetically disturbed period the coherence scales in the post midnight period are greater than that of in the pre midnight period. This suggests that magnetospheric electric field generated in storm time causes increase in coherence scales but shows large increase after midnight.

The paper reports night time observations of ionospheric irregularities made through amplitude scintillation of 251 MHz signal at Kolhapur (16.4 degrees N, 74.2 degrees E), an equatorial Appleton anomaly region using spaced antenna system. Monthly and night time percentage of occurrence of scintillations, during increasing solar cycle from January 2011 to August 2015, is discussed. The parameters such as-maximum cross-correlation function (C-I), Fade Rate are also studied. The percentage occurrence is observed to be higher in post sunset period and during equinoctial months than in winter and summer months. Scintillation occurrence is observed to be suppressed during increasing solar activity. C-I shows seasonal changes. Percentage of occurrence of C-I >= 0.5 decreases with increase in solar activity and fade rate also shows solar activity dependence.

All Sky Imager (ASI) data of over 351 nights with OI 630.0nm emission recorded during 2011 to 2015 (increasing phase of 24th solar cycle) are analyzed to study the percentage occurrence of EPBs. The ASI is installed at low latitude station Kolhapur (16.8°N, 74.2°E, 10.6° dip. Lat.) which has 140° field of view (FOV). In this paper we have studied hourly, daily, seasonal and yearly percentage of occurrence of EPBs and their variation with solar and magnetic activity. The EPBs onset occurs at around 20:00 IST and extends towards dawn with a peak around midnight. We analyzed all the disturbed nights (Ap>18) from the period of 2011 to 2015 and observed that the magnetic activity suppresses the occurrence of EPBs. Also the EPBs are fairly correlated with solar activity (10.7cm solar flux).

In this paper we have focused on drift of irregularities using amplitude scintillations for period January 2011 to December 2015. The data of VHF amplitude scintillations and all sky imager at Kolhapur has been used to obtain the drift of ionospheric irregularities. The drift is compared with velocities of thermospheric wind obtained by HWM−07 (Horizontal Wind Model-07) and of EPBs (Equatorial Plasma Bubbles). The results are in good agreement with model data. Also, the pattern of drift in scintillation data matches well with velocity of EPBs, mainly during equinoctial months. To examine the possible effect of magnetospheric disturbance on the dynamics of the irregularities we have compared the drift on magnetically disturbed nights with the monthly averaged quiet nights drift. Zonal velocity pattern on magnetically disturbed nights shows reversal in the direction of eastward zonal drift around midnight. The deviation of plasma drift on disturbed nights from monthly averaged quiet night drift shows maximum effect of magnetic activity around midnight. The monthly averaged peaks of the zonal drift increases with increasing 10.7cm solar flux.

The quiet-time daily variations of the cosmic radio noise at polar, auroral, sub-auroral and mid-latitude stations during period of solar minimum are utilized to develop the quiet day pattern of co ...

Abstract Copper sulfide-selenide (CuS0.2Se0.8) thin films were deposited on FTO coated glass substrate (fluorine doped tin oxide) and stainless steel substrates using electrodeposition technique. Deposited thin films were characterized using different characterization techniques viz. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, photoluminescence spectroscopy and surface wettability. XRD study showed polycrystalline nature with cubic phase of the films. Scanning electron microscopy showed that the surface area of the substrate was covered by the nanoplatelets structure of a thickness of 140 to 150 nm and optical study showed that the direct band gap was ~1.90 eV. Surface wettability showed hydrophobic nature of the CuS0.2Se0.8 thin films.

This work about the zonal drift velocity and signature of equatorial plasma bubbles (EPBs) by measurements of global positioning system (GPS) receiver and all sky imager (ASI) operating in India, at the low latitude region. The optical and radio observations have been made from Kolhapur (16.8°N, 74.2°E) and Hyderabad (17.37°N, 78.48°E), respectively. The zonal drift velocity of EPBs has estimated using images of nightglow OI 630.0nm emission recorded by ASI at Kolhapur. The measurements of total electron content (TEC) using the GPS have carried from the nearby station, Hyderabad. When depletions occurred about 00:37h (IST) in TEC, the EPBs were found to occur about 5:30h in optical data of OI 630.0nm emission. This work focuses on simultaneous measurements of TEC and intensity of OI 630.0nm emissions for EPBs during nighttime. The occurrence period of EPBs in TEC and OI 630.0nm has found to be different. To study this difference, the zonal drift velocity of EPBs has established. The averaged eastward velocity of EPBs was found to be 138m/s. The calculated values of zonal drift velocities are well correlated with that of the empirical model values. This work may be helpful in finding the growth of EPBs over low latitude.

This paper presents observations of plasma blobs by nightglow OI 630.0 nm emissions using ground-based techniques, all sky imager and photometer from Kolhapur. The nightglow observations have been made at low latitude station, Kolhapur (16.42°N, 74.2°E, and 10.6°N dip lat.) during clear moonless nights for period of October 2011–April 2012. Generally, these occur 3 h after sunset (18:00 IST). Herein we have calculated velocities of plasma blobs using scanning method, introduced by Pimenta et al. (Adv Space Res 27:1219–1224, 2001). The average zonal drift velocity (eastward) of the plasma blobs were found to be 133 ms−1 and vary between 100 and 200 ms−1. The width (east–west expansion) and length (north–south expansion) of plasma blobs is calculated by recently developed method of Sharma et al. (Curr Sci 106(08):1085–1093, 2014b). Their mean width and length were in the range of 70–180 and 500–950 km respectively. The study shows that localized eastward polarization electric field plays an important role in the generation of plasma blobs.