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

Phillip Valek

Auburn University and Southwest Research Institute

Abstract:

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 energy 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 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.