Faraday rotation observations of an Alfven wave at 4 solar radii during the January 9, 1983 superior conjunction of the Helios spacecraft were simultaneously obtained in Goldstone, California and Canberra, Australia allowing the measurement of the Alfven wave speed. We find that the T. Hoeksema et al. (1982) potential field source surface model performs better than the M. Paetzold et al. (1987) magnetic field magnitude model for predicting the magnitude of the magnetic field in the region based on the observed Alfven speed. Assuming the Alfven wave is monochromatic, coherent, and radially propagating, we determine the minimum magnetic field fluctuation required to reproduce the observations. We use the minimum magnetic field fluctuation to calculate the minimum Alfven wave energy flux of 6 × 10¹⁹ W; this is approximately 20% of the wave energy required to accelerate the solar wind.