Nonlinear shock structure in a weakly ionised magnetoplasma

Abstract. The formation of a neutral induced weak nonlinear shock structure in a weakly ionised magnetoplasma has been analytically investigated. Using the reductive perturbation method, basic dynamical equations of a three-component (electron, ion and neutral) plasma have been reduced to a well-known Burger equation which can support a weak shock solution. Its stationary and initial value solutions have been derived to describe the characteristics of the weak shock profile. Asymptotic behaviour of the Burger solution results in a saw-tooth structure which has a practical implication to predict the nonlinear steepened structure of the nighttime irregularity in the lower portion of the Earth's ionosphere. Accordingly, it is suggested that the observation of saw-tooth shape of nighttime irregularity at 92 km could be attributed to the nonlinear saturation of the NILF mode instability as proposed by Dwivedi and Das in 1992. However, exact experimental verification of this suggestion requires more data on nighttime irregularity in the mesosphere and lower thermosphere (80-95 km) for a wide range of scale sizes extending up to about 1 km and above.