Perkins instability revisited

A thorough review of the Perkins instability is presented in this paper. We introduce two new elements to the earlier model presented by Perkins [1973], namely, the neutral wind velocity and gradients in the background field line integrated density and Pedersen conductivity, respectively. We derive the eigenfrequencies and growth rates for a new instability and recover the limiting cases discussed by Perkins [1973] and Miller [1997]. The presence of gradients in the background density and Pedersen conductivity reveals a new branch in the dispersion relation and can possibly enhance the Perkins instability growth rate. The need for horizontal gradients, as was pointed out by Basu et al. [1981], is essential for the generation of small‐scale and kilometer‐scale irregularities. The Perkins instability is shown to be enhanced by both the presence of a neutral wind and the background density and Pedersen conductivity.