Spatial and temporal structuring of nighttime intermediate layers above Wallops Island.

摘要

The research presented here describes the phenomenon of intermediate ion layers, their composition and evolution. A NASA sounder rocket launched from Wallops Island, VA (37.84 N, 75.48 W) on 30 June 2003 at 2:50 EST made the first ever in situ measurement of the relative concentrations of Fe +, Mg+, NO+, and O2 + within a nighttime intermediate layer below 140 km altitude. Ion composition measurements were made from 80--220 km altitude and included observations of three separate regions having high concentrations of metallic ions: the intermediate layer at 118 km, a sporadic-E layer at 105 km, and a third layer above 160 km. This payload was preceded by two others that measured electron densities and made TMA chemical tracer releases at 23:19 and 1:41 EST and followed by another at 3:07 EST. The composition observations demonstrate that metallic ions may be a significant source of ionization in the nighttime E and F region ionosphere at midlatitudes and that the relative ion composition within intermediate layers may fluctuate significantly over horizontal scales of 100s of km. The sequence of measurements has allowed us to demonstrate that intermediate layers cannot be treated as flat layers over a scale of 100s of km and that internal gravity waves can lead to the formation of plasma layers in the nighttime lower F and upper E region ionosphere.