Goutam Kumar Sen

Comparative study of the physico-chemical parameters of the coastal waters in rivers Matla and Saptamukhi: Impacts of coastal water coastal pollution

A qualitative and quantitative research has been performed on the physico-chemical parameters of the neighboring coastal waters of the rivers Matla and Saptamukhi in the Sunderban district, West Bengal. The distribution pattern of eight physico-chemical parameters, namely pH, salinity, dissolved oxygen, suspended solids, nitrogen and phosphorus concentrations (inorganic and total) has been graphed and compared for the two rivers over a time period of ten years (’90s decade). A statistical analysis has been carried out and the correlation data between these parameters has been rationalized based on both natural and man-made activities during that time. This has pointed to various causes behind coastal pollution of river waters. The changes in water quality have been related to flood impacts, storm surge, eutrophication, domestic sewage, agricultural and industrial wastes. In order to avoid coastal degradation and maintain environmental balance, it is very important to understand the impact of these parameters on coastal zones.

Modulational instability from an intense elliptically polarized electromagnetic wave in a homogeneous unmagnetized plasma

Nonlinear propagation of an elliptically polarized electromagnetic wave through plasma medium is marked by the development of precession of its polarization ellipse. The nonlinear frequency shift due to weak relativistic mass variation and the Lorentz force can cause a modulational instability of a large amplitude wave, which also gives rise to instability in the precession of the polarization ellipse. The latter phenomenon is discussed here.

Coastal water pollution in two rivers of the Bengal delta

A thorough comprehension of relevant environmental parameters is a prerequisite to preventing coastal degradation and environmental balance in coastal zones. In this study, we correlate major physicochemical of two coastal rivers (Matla and Saptamukhi) in the Sunderban district, West Bengal. The parameters namely: pH, salinity, dissolved oxygen, suspended solids, nitrogen and phosphorus concentrations (inorganic and total) of these two rivers were studied in detail over the 90s decade. We hypothesized that both natural and anthropogenic activities during that time have contributed to the pollution and employed the above parameters to test our hypothesis. Our results reveal that the quality of waters in the rivers have been showed to be dependent on flood impacts, storm surge, eutrophication, domestic sewage, agricultural and industrial wastes. Thus, both natural and anthropogenic causes are the behind coastal pollution of river waters. We conclude that they have all contributed to pollution of these rivers in various ways and we calculate the differential effects of these parameters on coastal pollution.

An Investigation into Height Variation of Ionospheric Signature Due To the Cyclonic Storm Formation Using COSMIC-RO Measurements

Here the height dependence of ionospheric signature due to the existence of low pressure systems, like, Cyclonic Storms (CSs) at the lower atmosphere, have been studied using COSMIC-RO satellite measurements on the example of two deleterious cyclones – Mahasen (10-16 th May 2013) and Phailin (8-14 th October 2013). These two CSs were generated over the Bay of Bengal (BOB) in 2013. Day-to-day variations of four different physical parameters, namely, IEC, NmF2, HmF2 and the NOAA Outgoing Long Wave Radiation (OLR) have been retrospectively analyzed during the Cyclone Genesis Period (CGP). For the first time, five 50 km width ionospheric layers have been considered to rectify the dominant perturbation zone linked to the considered lower atmospheric convective activities. All the ionospheric parameters exhibit excellent correlation between themselves whereas OLR exhibit little correlation with the ionospheric parameters. Both, pre-cursor and post cursor signatures have been registered at the ionospheric F2 layer in the pre and post Cyclone Life Cycle (CLC). Here, the dominant perturbations were mostly confined in the layers associated to lower F region of the bottom side Ionosphere and it is gradually decreasing for the upper layers. Moreover, few discrepancies which were detected in case of two CSs were mainly due to dissimilar strength of CSs and difference of sampling size of ionospheric data. Atmospheric Gravity Waves (AGWs) is assumed to be the main responsible coupling agent between lower atmosphere and Ionosphere during this type of lower atmospheric convective activities, like CSs.

Climatology of ionosphere over low-latitude (Kolkata) using FORMOSAT-3/COSMIC satellite observation

We have analyzed the diurnal, monthly, and seasonal variation in NmF2, HmF2, and IECs parameters derived from the COSMIC-RO observation over the low-latitude (Kolkata) region during 2008–2012 and compared the result with the IRI-2007 model output. In general, during HSA period the seasonal averaged model outcome prominently overestimates the observed values throughout the day, except HmF2, while in LSA period it is confined to post-noon hours. The differences between diurnal-dip and diurnal-peak values of all these parameters are considerably higher in the model outcomes than those of observed values, especially during increasing solar activity. In addition, the monthly averaged NmF2, BIEC, and TIEC values at noon and midnight, obtained from the both options, exhibit semi-annual variation, which are in good agreement with some earlier studies, whereas HmF2 shows annual variability for all solar activity. Moreover, the similarities and dissimilarities observed in variation pattern, particularly during 2011 and 2012, can help the research community to understand the recent trends of ionospheric parameters and develop the IRI model with more efficiency to fit the observed profile in a better way.