Residual intensity fluctuation measurements within the wings of the 25183.6 MgI bl line, obtained from two, high-resolution, high-dispersion, Sacramento Peak Observatory spectrograms, have been subtracted from intensity fluctuations in the adjacent continuum in order to isolate fluctuations associated exclusively with line formation. The useable spectral range for studying these lineformation fluctuations is restricted to wavelengths between 1040 and 7170 km because the subtraction increases the relative importance of noise and large-scale photographic variations across the spectrograms could not be completely removed. Power and cross-power (coherence and phase) spectra proved to be valuable diagnostic tools in isolating line-formation fluctuations.
Over this spectral range, the line-formation fluctuations are characterized by flat power spectra as compared to those for continuum fluctuations, appreciable fluctuation rms relative to that for continuum fluctuations, and the necessity to multiply the wing fluctuations by a factor 0.95 ~< 0~min ~< 1.00 to most effectively isolate these fluctuations (Figures 3 and4). That continuum fluctuations are modified in shape but otherwise not drastically changed in the line wings explains the fiat spectrum. The relative rms's vary from 0.34 in the inner wing to 0.22 in the outer. The range of possible values for 0;rnin results from uncertainties in the photographic density-residual intensity calibration.