Availability of MDI full-disc Doppler data
since the start of mission. Two plots, are shown one for the
start of mission through 1998.08.16,
and the other for
1998.08.16 through present. Each plotted
point corresponds to the fractional coverage (pixels available divided by
the full image size for each minute) during a 1664-minute interval centered
on a time at which the central heliographic longitude of the disc is
0 mod 15 degrees, as discussed in the text. The primary cause of data
loss is missing images (interruptions due to different observing programs
and coverage by the Deep Space Network), but a small percentage of the
data loss is also due to telemetry errors. The latter cause the image
to be truncated at some random point, and since the readout order is
always the same, south to north, there is slightly better coverage the
farther south on the Sun we go. This is, however, a very small effect,
accounting for only a few percent of the total data losses. The shaded
intervals are those analyzed here. In general the ring-diagram analysis
procedure is difficult when the coverage in an interval of this length
is less than 0.7 - 0.8.
Comparison of the depth dependence of inferred
flows for an 8-day interval in June 2000 from the two analyis methods.
Figure 2.1 shows the zonal component as determined by the
(a) RLS method and by the
(b) OLA method.
Figure 2.2 shows the corresponding meridional components:
(a) RLS method;
(b) OLA method.
The error bars represent the formal uncertainties from the inversions.
Summary profiles of the horizontal flow fields,
averaged over full rotations and all longitudes, as functions of depth
and latitude, for selected rotations in
Note that the directions of the flow vectors are unrelated to the directions
of the axes. Although latitudes increase northward to the right, an arrow
to the right represents a positive zonal (westward) velocity relative
to the differentially rotating coordinate frame at the given depth and
latitude.