On the coupling of layer instabilities in the nighttime midlatitude ionosphere

Abstract

[1] There are two plasma-structuring mechanisms that are known to operate at night in the midlatitude ionosphere, the Perkins instability (Perkins, 1973) in the F region, and the more recently discovered sporadic-E layer (E s L) instability (Cosgrove and Tsunoda, 2002) in the E region. Both are layer processes, whose coupled response has been shown to be more unstable than either by itself . Derived growth rates, however, were given only in terms of the most unstable mode; exactly how the individual growth rates in the E s and F layers are affected by coupling remains to be shown. To do so, simplified descriptions of the instabilities are derived in this paper to show that the growth rates of both layer instabilities are enhanced by additional vertical drifts produced by polarization electric fields that map between regions along geomagnetic field lines. Key findings are (1) largest enhancement is in the growth rate of F region structure (g P c ), (2) g P c is controlled by the E s L instability, and (3) additional positive feedback to the E s L instability occurs because of its dependence on the field-line-integrated Pedersen conductivity of the F layer. An important byproduct of this study is the finding that a more consistent interpretation of existing data is possible, if we assume that the coupled system involves a large-scale, but finite-sized, E s patch. These new findings seem to explain several puzzling observations that are associated with midlatitude spread F.

Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

“…For example, they contribute to the formation of traveling ionospheric disturbances (TIDs) (e.g., Hines, 1960;Huang et al, 1994;Kirchengast et al, 1995;Vadas and Liu, 2009). In addition, it has been shown that there exists correlation between TIDs and sporadic E layers (Tsunoda, 2006), and the variations of sporadic E layers are influenced by both tides (e.g., Arras et al, 2009) and GWs (e.g., Woodman et al, 1991). Theoretical studies showing the importance of GWs in the T/I are presented by Vadas and Fritts (2005), Vadas and Fritts (2006), Vadas (2007), Fritts and Vadas (2008) and Yigit et al (2008).…”

Climatology of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) in the Central Pacific and South American sectors

“…Huang et al (1994) identified gravity waves as a plausible explanation for driving MSTIDs in the bottomside F region, thus enhancing their growth rate. There is also a growing body of literature exploring E region coupling effects, through which the polarized electric field from a sporadic E layer maps efficiently to the F region, providing the seeding mechanism for MSTIDs (Tsunoda and Cosgrove, 2001;Cosgrove, 2004;Tsunoda, 2006;Yokoyama and Hysell, 2010).…”

Interaction of plasma cloud with external electric field in lower ionosphere

“…4. Hysell and Burcham (2000); Hysell et al (2002);720 Y. S. Dimant and M. M. Oppenheim: Plasma cloud in ionosphere: effect of external field Yokoyama et al (2004) performed 2-D and 3-D numerical simulations of cloud polarization, current closure, and E-F region coupling, including the recently predicted sporadic-E instability Tsunoda, 2002b, 2004;Tsunoda et al, 2004;Tsunoda, 2006). These simulations give spatial distributions of the electric field but, being performed for particular cases only, provide no parameter dependencies as we will provide.…”