Investigations of the Ionospheric Alfvén Resonator at auroral latitudes
In this thesis both ground-based and space-based data are utilized to study the effects of the Ionospheric. Alfven Resonator (IAR) at auroral latitudes. Central to the investigation is a modulated heating experiment at Tromso, Norway on 8th October 1998 which constituted the first satellite detection of artificially excited ULF waves. Alfven waves were detected in electric field data collected by the FAST satellite. The downward electron flux data contains the first observations of electrons undergoing acceleration within the IAR due to parallel electric fields associated with the artificially stimulated Alfven waves. The time history and spectral content of the downward electron fluxes is investigated, and found to be consistent with the existence of a localized region of oscillating parallel electric fields at an altitude of âˆ¼3400 km. This caused the periodic acceleration of suprathermal electrons towards the ionosphere. EISCAT UFT electron and ion temperature and density profiles were used in conjunction with neutral density profiles from the MSIS E-90 model and tristatic velocity measurements to determine the magnitude of the current source that launched the Alfven waves. This was used as an input into a simple 1-D model of the IAR first developed by Traktengerts et al.  to investigate the range of conditions required for successful satellite-wave detection.;To support the IAR interpretation, natural resonance features of the IAR observed in pulsation magnetometer data from the high latitude station of Sodankyla are investigated during the month of October 1998. A new technique is developed to determine the diurnal evolution in frequency of IAR resonance features for 10 time intervals in October 1998. EISCAT UHF electron density profiles are used to determine the reflection coefficient at the lower IAR boundary, Rlower, which is compared to the magnetometer analysis results. The investigations in this thesis shed new light on the nature of the IAR and future field-line tagging experiments.