Ronksley, A; (2016) Optical Remote Sensing of Mesoscale Thermospheric Dynamics Above Svalbard and Kiruna. Doctoral thesis , UCL (University College London).

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Abstract

Vertical winds are key in thermospheric dynamics and only until recently have the detectors been sensitive enough for them to be measured accurately. Two narrow field Fabry-Perot Interferometers (FPIs) are used as well as one state-of-the-art all-sky FPI, SCANning Doppler Imager (SCANDI), which is capable of simultaneous measurements across the sky at high spatial and temporal resolution. They measure the atomic oxygen 630nm emission line which peaks in brightness at 240km altitude in the upper thermosphere region. Emission intensities, line-of-sight wind speeds and neutral temperatures are obtained. SCANDI’s existing infrastructure has been developed based upon the requirement to upgrade the sky map to higher spatial resolution, for the onset of solar maximum. The calibration methods and data analysis are presented. The wind-fitting algoithm is shown for the new map trigonometry. This fitting is verified by producing climatological horizontal wind-fields in a dial plot format and cross-comparing with SuperDARN climatologies. A statistical analysis of the vertical winds from 2002-2009 is presented leading to the possibility of ‘black swan events’ around midnight in the polar cap. These are events which are thought impossible but are, in reality, found to have a small finite chance of occurrence. An investigation into the mechanism of the generation of these events leads to the discovery of hydroxyl contamination in the Svalbard data set. A spectral simulation of the 630nm and the hydroxyl lines allows the determination of an emission intensity threshold of 40R (10R) below which the wind (temperature) values are significantly affected. The Svalbard data set is re-analysed excluding the contaminated data and a clean, more reasonable data set is presented with no black swan events. A statistical study of the relationship between the vertical and horizontal components of wind is presented showing the Burnside relationship is unsuitable for representing highlatitude winds. The CMAT2 atmosphere model data is used to assess which of Burnside et al’s (1982) assumptions are violated. The CUSPN campaign is presented showing the first results of the charged and neutral cusp region being simultaneously and independently measured using the EISCAT Svalbard Radar and the FPIs. Characteristic upwellings are observed concurrent with cusp precipitation and flux transfer events, which provides compelling evidence of high altitude ion-frictional heating.

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