Abstract
The stability and instability properties of electron acoustic (EA) waves which was recorded during Viking orbit 1188 in the dayside auroral zone have been theoretically investigated in this manuscript. The system under consideration is a magnetized collisionless plasma consisting of cold electron fluid, non-thermal hot electrons, electron beam and a stationary ions. The reductive perturbation theory have been used to get Zakharov-Kuznetsov (ZK) equation, obliquely propagating solitary wave solution have been derived. Nonthermality population parameter mu, densities ratios (alpha, beta), temperatures ratios (theta, sigma) and obliqueness angle upsilon affect the amplitude and width of EA solitary waves. The small k perturbation technique have been applied to ZK equation to study instability criterion in this system and finally the growth rate of the predicted instability dependence on the plasma parameters have been introduced, it was shown that plsma parameters sigma, alpha, mu, beta and the direction cosine (iota (zeta) , iota (eta) ) affects the instability growth rate Gamma.