[1] Department of Science and Humanities,College of Science and Technology,RUB,Bhutan
[2] Department of Mathematics,R.G.Baruah College,Guwahati-781025,Assam,India
[3] Centre of Plasma Physics,Tepesia,Sonapur,Assam,India
[4] Physical Science Divison,Institute of Advanced Study in Science and Technology,Vigyan Path,Garchuk,Guwahati-781035,Assam,India