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Title: Polar mesospheric summer echoes studied by active radio wave experiments
Author: Routledge, Graham John
ISNI:       0000 0004 2744 9254
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2011
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Polar Mesospheric Summer Echoes (PMSE) are a high latitude mesosphere phenomena that are observed at an altitude of '"'-'80 to 90 km. PMSE are a rela- tively new dusty plasma discovery, with the first documented observations in the 1980s. With the emergence of incoherent scatter radars over the past four decades, as well as coherent radars, the study of PMSE has increased. This is in part due to implications that PMSE are an indicator of global climate change. The presented .. thesis focuses on trying to determine the degree of electron temperature enhance- ment during active radio wave experiments and the effect this has on PMSE. Currently there are no conclusive measurements of electron temperature in the PMSE layer. Knowing the temperature value would allow theoretical estimates to be made of the dust size and densities within the PMSE layer. This thesis shows that the statistical PMSE modulation for a fixed high frequency heater-induced modelled electron temperature enhancement appears to be independent of alti- tude, and that currently accepted electron temperature models may over-estimate temperature values during PMSE heating. Additionally, it is demonstrated that for PMSE-only heating experiments the available IRIS riometer absorption data shows no absorption increase during artificial heating, from which electron tem perature values could have been determined. PMSE are most commonly studied at VHF and UHF frequencies. In this thesis PMSE modulation is observed at HF radar wavelengths. Theory and modelled predictions state that shorter VHF wavelengths correspond to the temperature-dependent electron diffusivity. How- ever, the longer HF wavelengths correspond to dust charging dynamics. The abil- ity to investigate PMSE at a new, third frequency range allows the study of dust charging dynamics, and for the first time this qualitative concept of dusty plasma is confirmed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available