Because of the plasma embedded in a static magnetic field, the dispersiveness in the Korteweg-deVries (K-dV) equation varies, thereby changing the inherent structure of the plasma-acoustic wave. It is quite difficult to solve the nonlinear wave equation derived in such circumstances, and thus to study the soliton dynamics in plasma-acoustic mode. A recent formalism, known as sine-Gordon method, has been developed to solve the modified K-dV equation derived with higher order dispersive effect. The method has its success in finding the solitary wave solution along with an exciting observation on the formation of narrow soliton wave-packet, wherein a continuous intensification of electric field pressure occurs. In addition, the solution explains the phenomena of radiation associated with soliton propagation.