Lidar and Modeling Studies of the Mesospheric Iron and Sodium Layers
Kane, Timothy Joseph
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https://hdl.handle.net/2142/71980
Description
Title
Lidar and Modeling Studies of the Mesospheric Iron and Sodium Layers
Author(s)
Kane, Timothy Joseph
Issue Date
1992
Doctoral Committee Chair(s)
Gardner, C.,
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Abstract
The mesospheric metals are believed to be the product of meteoric ablation. Very thin and brief layers observed in our lidar data, attributed to recently ablated meteors, are used to examine this hypothesis. The altitude distribution of these trails is compared to a model of meteoric deposition, meteor radar data, and average Fe and Na density profiles. The total meteoric influx is derived from our data and argued to be a lower limit on the actual meteoric influx.
Sporadic layers are very dense, thin, long-duration enhancements in the mesospheric metals. Two case studies of sporadic Na (Na$\sb{\rm s})$ layers, which provide insight into the true nature of these puzzling phenomena, are presented here. The first, concerning data collected during the AIDA-89 campaign in Arecibo, Puerto Rico, explores the connection between Na$\sb{\rm s}$ layers and sporadic-E (E$\sb{\rm s})$ layers. Following this, several Na$\sb{\rm s}$ layers observed during the ALOHA-90 airborne lidar campaign over the mid-Pacific are analyzed. The results indicate that sporadic layers can extend horizontally over thousands of kilometers and can be strongly influenced by atmospheric dynamics.
Finally, a lidar and modeling study of the mesospheric Fe layer at Urbana is presented. Strong seasonal variations in the Fe layer abundance, height and width, quite different from those observed in the Na layer, are demonstrated. A simple chemical model is developed and shown to predict the Fe layer shape as well as these seasonal variations. According to our results, the Fe layer column abundance will decrease dramatically over the next century in response to predicted cooling due to global change. Numerous sporadic Fe (Fe$\sb{\rm s})$ layers were observed and found to have characteristics different from those for Na$\sb{\rm s}$ layers. Our model suggests that Fe$\sb{\rm s}$ layers form by a two-step neutralization of Fe$\sp+$ brought on by excess electrons found in sporadic-E layers.
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