Measurements of Frequencies of Solar Oscillations from the MDI medium-l Program

by E.J. Rhodes, Jr., A.G. Kosovichev, P.H. Scherrer, J. Schou & J. Reiter

• Images

  • Fig. 1a: Mode frequencies.
    The multiplet frequencies determined from the MDI 144-day observing run using the averaged-spectrum method are shown as the small blue dots. Ridge-fit frequencies determined with the averaged-spectrum method as applied to entire p-mode ridges rather than individual modal peaks are shown as the red dots along the extensions of the ridges toward higher degrees and frequencies. The formal frequency uncertainties obtained from the averaged-spectrum method are superimposed upon both the modal and ridge-fit frequencies in yellow. For frequencies below 5 mHz the frequency uncertainties of the modal fits were multiplied by a factor of 1000 before being plotted. For frequencies greater than 5 mHz the uncertainties of the ridge fits were multiplied by 100 instead. The uncertainties of the ridge fits below 5 mHz were not modified. This figure may be compared with the m-averaged spectrum shown in Fig.1b.

  • Fig. 1b: Power spectrum.
    Power spectrum obtained from 144 days the MDI Medium-l data for the modes averaged over the azimuthal order m. The power concentrates in ridges corresponding to solar acoustic (p) modes. The lowest weak ridge corresponds to the fundamental (f) mode.

  • Fig. 1c: Full disk Dopplergram. (full-scale version)
    Full-disk Dopplergram obtained with MDI on 9 July 1996. The large left-right variation is the signal from solar rotation. The "texture" is a combination of the motion from the sound waves that permeate the Sun and the large convective cells called "super-granulation". The bright feature in the lower right quadrant is an active region.

  • Fig. 1d: Medium-l Dopplergram.
    A Medium-l Dopplergram that is binned with Gaussian weights on a square 5x5-pixel grid as described by Kosovichev et al. (1996). The Medium-l Program of the SOI/MDI experiment is dedicated to the nearly-continuous monitoring of the Doppler velocity field of the visible solar hemisphere. The Medium-l data are transmitted though the low-rate (5 kbps) telemetry channel of SOHO. It is this relatively low bit rate which limits the spatial resolution of the Medium-l observations. This low data rate also requires that some initial processing of the original 1024x1024-pixel CCD full-disk Dopplergrams be carried out on board the MDI instrument.

  • Fig. 10: Inversion results.
    Relative differences between the squared sound speed in the Sun and a standard solar model as inferred from inversions of the frequency estimates computed with the mean-multiplet method (red) and the averaged-spectrum method (blue) from the MDI Medium-l data. The horizontal bars show the spatial resolution of the inferred values, while the vertical bars are the formal error estimates.

• Movies
  • 5 hours of MDI Medium-l data, 96/09/01
    • MPEG movie (large version) (~4.1Mb)
    • MPEG movie (small version) (~2.1Mb)
  • 10 hours of MDI Medium-l data, 96/09/01
    • MPEG movie (large version) (~8.1Mb)

• Solar Sounds (obtained from 40 days of MDI disk-averaged data speeded up by a factor 42,000)
  • one mode: l=1,n=20, nu=2.94-3.0 mHz
    • AIFF Format (~7Mb) (16-bit, 44.1 kHz sampline rate)
    • AU Format (~7Mb)
  • three modes: l=0,n=21, l=1,n=20, l=2,n=20, nu=2.95-3.05 mHz
    • AIFF Format (~7Mb) (16-bit, 44.1 kHz sampline rate)
    • AU Format (~7Mb)
  • all low-degree modes: l=0,1,2, and 3
    • AIFF Format (~7Mb) (16-bit, 44.1 kHz sampline rate)
    • AU Format (~7Mb)

• Tables of Frequencies of Solar Oscillations from 144 Days of MDI Medium-l Data
  • Table 1: Frequencies of solar oscillations obtained from 144 days of MDI Medium-l data using the averaged-spectrum method.
  • Table 2: Frequencies of solar oscillations obtained from 144 days of MDI Medium-l data using the mean-multiplet method.
  • Table 3: The averaged-spectrum frequencies of a mode subset that is common to the mean-multiplet frequency set.
  • Table 4: The mean-multiplet frequencies of a mode subset that is common to the averaged-spectrum frequency set.

• Inversion Results
  • averaging kernels, A(r,r0), at r0/R=0.0625, 0.125, 0.1875, 0.25, 0.3125, 0.375, 0.4375, 0.5
  • averaging kernels, A(r,r0), at r0/R=0.5625, 0.625, 0.6875, 0.75, 0.8125, 0.875, 0.9375
  • sound-speed profiles from the averaged-spectrum frequencies
  • sound-speed profiles from the mean-multiplet frequencies

• Oscillation Power Spectrum from 144 Days of MDI Medium-l Data (binary FITS files)
  • m-averaged power spectrum of modes of l=0-299 with 103,680 frequency points, 0.0803755 microHz frequency resolution. This file is in FITS format (~124.5 MB).
  • a smaller version of the spectrum with 1296 frequncy points, 6.43 microHz frequency resolution (~1.6 MB).