Metallic ion transport associated with midlatitude intermediate layer development

Abstract

[1] Although intermediate layers are frequently observed by the Arecibo Incoherent Radar Observatory and by ionosondes around the world, many questions still remain regarding their formation, structure, and composition. In this paper, we explore the effect of metallic ions, specifically Fe + , on intermediate layer development and evolution. Several studies have demonstrated that layers can form from either molecular or metallic ions. This paper extends these earlier studies by quantifying the effect of metallic ions on intermediate layer morphology. We show that the efficiency of metallic ion transport depends significantly on the amplitude and wavelength of the imposed horizontal wind field. Specifically, larger amplitudes and longer wavelengths result in increased ion transport in the direction of the propagating neutral wind field.

Relative concentrations of molecular and metallic ions in midlatitude intermediate and sporadic‐E layers

“…Intermediate layer formation is still not completely understood, but the prevailing theory holds that shears in the neutral wind are responsible for vertical plasma redistribution [ Axford , 1963]. Numerical models indicate that intermediate layers can form without the presence of metallic ions, but that should any metals be present during formation the layers will eventually develop a significant metallic concentration [ Osterman et al , 1994, 1995; Carter and Forbes , 1999; Bishop and Earle , 2003]. The presence of metals above 160 km observed here suggests that there may have been metals present during initial layer formation if the intermediate layer began forming at those altitudes as is often observed elsewhere.…”

“…They occur at all local times, but are most distinct at night. The ion composition of these layers is a consequence of layer evolution and dynamics and is therefore of great interest to those trying to evaluate the accuracy of numerical models of intermediate layers [ Osterman et al , 1994, 1995; Bishop and Earle , 2003].…”

Ionogram height–time–intensity observations of descending sporadic E layers at mid-latitude

“…In the last equation, T and l z are the period and vertical wavelength of the tidal wind, H is a representative scale height for the lower thermosphere between 80 and 200 km, z 0 is a lower altitude boundary set equal to either 85 km for diurnal, or 95 km for semidiurnal tides, and t 0 is the phase of the tide at the representative scale height. The ion-neutral collision frequency profile between 80 and 200 km was based on a least-squares fit of the n i / o i altitude data used by Bishop and Earle (2003) as being more appropriate for metallic ion plasma in the lower mesosphere. With respect to the tidal parameters, these were kept similar to the ones used by Tong et al (1988) for the diurnal (semidiurnal) tide: T ¼ 24 h (12 h), l z ¼ 25 km (90 km), V 0 ¼ 20 m=s (3 m/s), z 0 ¼ 85 km (95 km), t 0 ¼ 9 h (5 h), H ¼ 5:5 km (5.5 km).…”

Terdiurnal signatures in sporadic <i>E</i> layers at midlatitudes

“…(1) Cartesian coordinates were used (x, y and z point eastward, northward and upward, respectively), which differs from the usual notations in literature. Considering that r 1 at atmospheric regions below ∼ 115 km (Bishop et al, 2003), the zonal wind is significantly more efficient at causing a vertical plasma motion.…”