Subject:  Coordinated SOI/MDI/SoHO Observations with La Palma

Topics to be investigated:

 Magnetic flux emergence and the evolution of magnetic fields

 Photospheric flows and their relationship with supergranules and
 magnetic patterns

MDI observations desired:

 High resolution mode - magnetograms, dopplergrams, continuum filtergrams

La Palma observations:

 G band & continuum filtergrams
 Ca II K filtergrams (3 A bandpass)
 5250 magnetograms

Discussion/Justification:

Simultaneous observations with SoHO/MDI and the Swedish Solar Vacuum
Telescope are a high priority for our studies of photospheric flows and
magnetic evolution. MDI provides very stable images over a long time
base but without the high spatial resolution available (sometimes) on
the ground. The more detailed pictures that we can get for several
hours on the ground will help us to see the smaller scale structures
(especially with the G band images) corresponding to the MDI magnetograms.
These G band images will also allow better tracking of photospheric
flows than the MDI continuum filtergrams and in fact will provide
a crucial calibration of the latter. We are able to construct flow
maps from MDI continuum images but we suspect that the marginal resolution
is having some effects on the results. It is essential to observe
simultaneously from the ground to understand these effects.

We also want to obtain images in the upper photosphere/chromosphere to
follow the initial phase flux emergence process using a Ca II K filter
with a 3A bandpass. These K line movies show the initial phases of flux
emergence very well and subsequently show the motions of most of the
flux as bright points. This allows the unambiguous i.d. of bi-polar
pairs which is often not clear in magnetic movies alone; i.e., often it
is confusing who is whose partner and sometimes one partner is not
continuously visible in groundbased mgagnetograms. Hence it is possible
to follow and maybe do a proper inventory of the magnetic flux. The
flux emergence in the K filtergrams shows as a dark "puff" that
elongates to a spindle with bright points developing on either end. It
looks a bit like celluar mitosis.

It is important to have MDI observations during time periods that are
likely to have good seeing conditions at La Palma. The best times are
from about 8:00 to 10:00 UT. On rare occassions, the seeing can be
good all day but the above times provide the best odds.

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