Figure 1 shows the l-nu spectrum for the initial 60-day run of the medium-l program.
shows vertical slices at l = 100, 200, and 300 from the data in Figure 1. Note the low noise
levels and the clear power peaks up to the Nyquist frequency. Also note the asymmetry at low frequency.
Models of the upper reflection layer show similar asymmetry. the spacing of the peaks at high frequency
indicates the source of the acoustic modes is about 50 km below the photosphere.
Figure 3 shows the difference between observed and model sound speed as a function of depth in the Sun.
The "bump" just below 0.7 R indicates the possible location of excess turbulence.
Figure 4 shows the inferred rotation rate as a function of depth and latitude. Evidently the convection zone
rotates uniformly along a radius with all depths showing the differential rotation seen at the surface. Below
the convection zone is a layer of shear below which the radiative interior seems to rotate rigidly. This
shear zone which coincides with the sound speed excess could be the region where the solar cycle dynamo
Figure 5 shows an l-nu diagram from an 8-hour campaign of high resolution Doppler images. The ridges
are clearly visible to very high l.
Figure 6 is a comparison between the absolute value of the magnetic field (in color) and the simulated
surface velocity from the time-distance pictures (arrows). The longest arrow is for 1 km/s velocity.
Figure 7 shows a map of horizontal motions inside the convection zone. The colored shading indicates
Figure 8 shows a vertical slice into the Sun. The supergranule flow evidently extends only 3-4 Mm into
the convection zone. This is the latest analysis of this dataset with improvements to the tomographic
inversion code used to convert time-distance measurements into velocity and temperature maps.
Figure 9 shows the first analysis of motions in the upper part of the convection zone. The observations for
this type of analysis are unique to the SOHO-MDI instrument. The approximate location of the region is
shown on a schematic diagram of the Sun for scale.
Figure 10 shows a verification of the time-distance method of inferring motions. The panel on the left
shows a direct photospheric Doppler image while the image on the right was determined for very near
surface depths using time-distance methods.
Figure 11 shows an MDI high resolution magnetogram overlaid with lines of convergence of the horizontal
flow and with green dots showing the convergence points. The measured flow is shown as colored arrows,
red for inferred downflow and blue for inferred upflow. The field is shown light grey for positive fields and
dark for negative fields. Only field above the background noise is shown.
Figure 12 shows a typical full disk MDI magnetogram. The movie shows one magnetogram each 96
minutes for the end of April through September 1996. Full resolution views are also provided for the south
pole, north pole, and equatorial regions.
Figure 13 shows more detail in the magnetogram. All of the light and dark structure is field. The
background texture is leakage from granulation and is not magnetic field. The field is seen to be mixed
polarity within and on the boundaries of the supergranule network.
Figure 14 shows the list of "Campaign" observation sequences obtained with MDI during the initial 8-
months of normal operations. Calibrated datasets from most of these campaigns will be available for
science analysis within a few weeks.