Sunday, 9 January 2005
Using the TIEGCM to estimate the equatorial vertical E x B drift velocity with ground magnetic perturbation
Located at a distance of approximately 90-km above the Earth’s surface, the ionosphere is distinguished by a relatively high density of positively charged ions and negatively charged electrons distributed in several distinct regions. In part to facilitate the study of the ionosphere, the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) was developed. The TIEGCM is a self-consistent, three-dimensional time-dependent model of the Earth’s atmosphere. TIEGCM predicts winds, temperature, major and minor composition of the air, and electrodynamic quantities such as currents in the ionosphere, for the entire globe from 97 to approximately 500-km in altitude. Past observational studies suggested that the strength of the drift velocity could be inferred from ground magnetic perturbation. This method involves situating one magnetometer on the magnetic equator and another magnetometer placed six to nine degrees north or south of the magnetic equator. Such studies also quantified the relationship between equatorial ion drift velocity and magnetic perturbation. This research project assessed the TIEGCM's performance by comparing the quantified relationship from previous studies to TIEGCM outputs. Equatorial ion drift velocity and magnetic perturbation (dH) were analyzed to identify the strengths and weaknesses of the TIEGCM in comparison with the observation data set. The results revealed that the TIEGCM represents the observations quite well, however, there are still some unexplained variations. The results of this study are most significant because they have showed us that we still do not fully understand the mechanisms that produce upward E x B drift velocity and magnetic perturbation.