The line profile was scanned for 20 minutes with a repeat period of 15 sec. The system provides 10 independent spectral samples, each offset by about 30 mÅs from its neighbor. As a first step, all 80 scans are averaged together into points which are at fixed wavelength (as defined by the spectrograph). Precise offsets are determined to bring all profiles into coincidence at a point in the line where the intensity is 0.5 of continuum. These shifts are all applied and the center point is taken to be the wavelength zero point. A linear gain adjustment is applied to bring the line cores and continuua into agreement. All spectral samples are then combined into a single master average profile which is the average of all time dependent scans as well as all spectral samples. The master profile and a shifted average profile are available as text files. Differences between the master profile and the shifted average profile are very small due to the fact that intrinsic profile changes are almost as large as the smearing due to the doppler shift. The shifted average is plotted below:
For the time dependent profiles two separate scans are combined since the scan direction is alternated for a sampling rate of one pair per 30 sec. Each profile was formed by shifting and gain adjusting each of the10 spectral samples as in the formation of the master profile. These were compared to the master profile. The average intensity for each scan was retained although during each scan corrections for continuum intensity fluctuations were applied based on two non-scanning spectral samples.
Each of the 30-second profiles was shifted so that its bisector at an intensity of half the continuum coincided with the corresponding bisector for the master profile. The difference between each profile and the master was then calculated and normalized so that the average continuum level has a value of unity. The differences were then plotted for each and formed into a movie which is:
For quantitative analysis, the time resolved intensity profiles are available as text files. The file numbering starts with unity and is incremented by 1 for each successive 15 second integration. Thus the pairwise averaging provides only odd numbered files. Each table provides three numbers: the first column is the wavelength offset from the zero point of the master profile. The profiles in the tables have not been shifted to be centered on the master profile so differences between them are dominated by each one's doppler shift. The second column gives the intensity normalized so that its difference relative to that of the master profile is significant as a measure of the absolute change in continuum intensity. The third column gives the number of spectral sample points combined to form the tabluated line profile. This sampling is coarser than the original data to avoid irregularities due to the nature of the average. The file name OIN_n.TXT denoted that it is a binning output file of normalized intensities. The n is the index number of the starting file of the average. Thus line profiles 1 and 2 have been combined into adopted line profile included in OIN_01.txt.
The time dependent average intensity is determined from two spectral samples taken at fixed wavelengths in the continuum. Changes in this continuum intensity come from the intensity variation on the solar surface due to the acoustic oscillations as well as from passing clouds in the Earth's atmosphere. Since the continuum samples are measured continuously, the time resolution available is quite good. For the time range of the above observed profiles the continuum intensity is given by:
