Excitation of short‐scale density structures by drift waves during ionospheric heating

In this paper we investigate the role of dissipative drift instability in exciting “needle‐like” short scale density structures recently observed during ionospheric heating [ Kelley et al., , 1995; Franz et al. , 1999]. A two‐fluid model for a warm, collisional plasma column, representing a typical density striation is used to derive a dispersion relation for drift modes. It is found that unstable drift modes can be excited. More accurate nonlocal eigenmode analysis reveals that for Arecibo parameters, the m = 3 mode is most unstable. Mixing‐length estimate of the density spectrum indicates a k −2 scaling in reasonable agreement with the observed spectrum.