  Two-stream instability (TSI) is studied analytically in the lunar plasma
environment. The electrons in the solar wind constitute the electron-beam and
the lunar electron plasma constitutes the background plasma with which the
electron-beam interacts to trigger the TSI. The lunar plasma is considered to
have a variable proportion of the energetic (hot) electrons, 1% to 25% of the
total lunar electrons, along with the bulk thermal (cold) population. The
analysis shows that the presence of energetic electrons in the lunar plasma
environment modify the TSI dispersion relation and can have a significant
impact on the triggering of TSI and are capable of triggering nonlinear
phenomena by making the lunar plasma system unstable.
