Development of spacecraft borne instrumentation and analysis of low energy ionospheric outflow.

摘要

The scientific focus of this dissertation is on the Earth's low energy ionospheric plasma outflows. This study of magnetospheric physics is performed using spacecraft measurements of the relevant plasma populations. An understanding of the basics involved in the production of spacecraft borne instrumentation is useful when interpreting the data. This dissertation is therefore comprised of two parts, a discussion of instrument development for a specific case, and a presentation of results, from very different instruments, of the investigation of the low enemy ionospheric outflow. In part one, the Medium Energy Neutral Atom (MENA) imager, flown aboard NASA's IMAGE spacecraft, is used to illustrate the development processes associated with a space borne instrument. The design prototype development and calibration of the flight instrument are discussed. While MENA does not address low energy (100eV) ionospheric outflow, it does provide an excellent example of the processes involved in the instrument development. In part two, a discussion of the analysis of data relevant to ionospheric outflow is presented. Instrumentation flown aboard NASA's Polar spacecraft, while at low altitude (0.8Re), is used for the study of the low energy plasma outflows. The Thermal Ion Dynamics Experiment (TIDE), the Toroidal Imaging Mass-Angle Spectrograph (TIMAS), and Hydra are used to study the high latitude plasma populations. The dependence of the heating and outflow of dayside ionospheric ions upon spatial displacement from the equatorward edge of the cusp is investigated. A method similar to superposed epoch analysis is performed on the data set. Integral moments of the plasma velocity distributions are sorted as functions of the most equatorward boundary of magnetosheath ion precipitation. This study shows that the ionospheric plasma is heated and begins its outflow at a location equatorward of the equatorward boundary of magnetosheath ions. The magnetosheath ions appear to contribute little energy to the high latitude ionospheric outflows on the dayside. This indicates that the magnetosheath electrons, or processes associated with them, are the dominant source of ionospheric heating in this region.