Simulations of spacecraft measurements for the study of Joule/Ohmic heating and energetic particle precipitation in the upper atmosphere (Doctoral thesis)

Πυρνάρης, Παναγιώτης/ Pyrnaris, Panagiotis

The Lower Thermosphere-Ionosphere (LTI), at altitudes from 100 to 200 km, is the theatre of a multitude of phenomena related to the interaction between ions, electrons and neutrals. At the same time, the LTI is influenced by forcing from above, such as by solar irradiation, by energetic particle precipitation and by the deposition of large amounts of energy in the form of Joule heating, which maximizes within these altitudes. The LTI is also affected by forcing from below, such as by Gravity Waves and tides. However the quantification of these phenomena is largely unknown to this date, as this region has been largely under-sampled: aside from a small number of missions, such as the Atmosphere Explorers (AE) and the Dynamics Explorers (DE) of the 1970s and the 1980s, and sounding rockets, which provide snap-shots of the upper atmosphere, the only source of information is obtained from remote sensing measurements. However, remote sensing instruments can not provide comprehensive measurements of all the parameters needed for many of the processes related to plasma-neutral interactions. This thesis aims to describe the ways of calculating Joule heating with simultaneous in-situ measurements of all the parameters required for its determination and to highlight the variability that comes from the different implementations and assumptions of the approaches used. To achieve this, the Global Ionosphere/Thermosphere Model (GITM) and Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) General Circulation Models are used. These are physics-based models that provide self-consistently all the plasma and neutral parameters together with the electric fields that enter into the calculation of Joule heating. Results from the GITM and TIE-GCM are inter-compared and are also compared against several empirical methods that are commonly used to estimate Joule heating. It is found that all empirical methods underestimate the heating rates of the LTI region compared to the GCMs. In the framework of the thesis, results from several software tools are presented that have been developed for the calculation of Joule heating and the simulation of in-situ measurements. The simulated measurements are obtained using interpolation methods along the satellite orbit within the grid of GCMs. Error propagation is employed to estimate the dependence of the uncertainty of Joule heating on the individual uncertainties of each measurement and to determine the expected total range of uncertainty of the estimated Joule heating. The software developed in the framework of this thesis has been developed in the form of a set of tools for the analysis of in-situ missions and for the processing of GCMs outputs in the LTI region. In addition, some of the few existing datasets of in-situ simultaneous electron, ion, and neutral temperatures measurements are re-analyzed, as they constitute critical parameters yielding information of the thermal equilibrium in the LTI. These are measurements obtained by the AE-C, AE-D, AE-E, and DE-2 space missions, which took place in the late 1970s and early 1980s. These measurements are compared against the electron and ion temperatures obtained from Incoherent Scatter Radars (ISR). The re-analysis of the measurements of the aforementioned missions is carried out to assess the quality of the existing measurements, which constitute the basis for a number of existing empirical models, and to point out inconsistencies with respect to our current understanding of the thermal equilibrium of the LTI. The analysis revealed many cases where the assumed condition that Ti ≥Tn$ is not confirmed, where Ti is the ion temperature and Tn the neutral temperature. Possible causes that could explain the existence of such events are listed, including instrument effects, Gravity Waves, Plasma Caves and the Equatorial Fountain effect. As a conclusion, the need for new measurements in the LTI is underlined, with a primary focus on in-situ measurements, in order to shed more light onto the physical processes taking place in the LTI.
Institution and School/Department of submitter: Δημοκρίτειο Πανεπιστήμιο Θράκης. Πολυτεχνική Σχολή. Τμήμα Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών
Subject classification: Upper atmosphere--Measurement
Keywords: Χαμηλότερη Θερμόσφαιρα/Ιονόσφαιρα,Ανάλυση επιτόπιων διαστημικών μετρήσεων,Μοντέλα παγκόσμιας κυκλοφορίας,Lower Thermosphere/Ionosphere,LTI,In-situ satellite measurements,General Circulation Models
URI: https://repo.lib.duth.gr/jspui/handle/123456789/19967
http://dx.doi.org/10.26257/heal.duth.18657
Appears in Collections:ΗΛΕΚΤΡΟΛΟΓΩΝ ΜΗΧΑΝΙΚΩΝ & ΜΗΧΑΝΙΚΩΝ ΥΠΟΛΟΓΙΣΤΩΝ

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http://dx.doi.org/10.26257/heal.duth.18657
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