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Abstract
I have developed a computer program (Colorado Io Torus Emissions Package, or CITEP) to simulate emissions from the Io plasma torus, and have used it to examine the consistency of remote observations with Voyager in-situ data. The complex spatial structure and viability in the torus hampers inter-comparison of data sets because of differing viewing geometries and data types. CITEP removes these effects, thereby facilitating the comparison. CITEP also uses the most up-to-date atomic data, magnetic field model, and plasma distribution for modeling the data. I use CITEP to retreive information about the local density and temperature structure in the torus to aid in determining the mass and energy budget of the torus.
I find that the measured brightness in the UV is approximately 2 times greater than the model predicts. I examine several possible causes for the brightness discrepancy such as calibration errors, measurement accuracy, inaccuracies of the model, and torus variability, and find the most likely cause is a nonthermal electron energy distribution. I examine the effects of such a distribution. I also determine that the Voyager singly ionized oxygen mixing ratio should be revised downward based on fits to both the visible and UV data. I model extensively the visible singly ionized sulfur emissions observed by Schneider and Trauger (1993), and determine radial and longitudinal density and temperature at the finest resolution obtained yet. I show that the cause of observed visible longitudinal variations in brightness are due to variations in parallel ion temperature only. I also create a computer model of centrifugally driven radial diffusion in the torus and use it to explain the density and temperature spatial profiles I obtain.
