On the other hand, temporal resolutions of the order of a few seconds can be achieved and fall in the typical range of timescales where mechanisms like reconnection, turbulence and wave propagation are taking place. To achieve this, we take advantage of the shutterless exposure mode of EIT, that was tested and applied successfully during a first campaign in May 1997, and which allows to reach cadences of the order of 15 seconds. MDI magnetograms will be extremely useful to follow the evolution of small magnetic elements at the footpoints of coronal magnetic structures. This would in turn imply reducing the nominal cadence of 15 sec.
Coronal holes seem thus to be too faint.
On the other hand, bright points and active regions are prime targets. For improved contrast and reduced confusion, on-disc targets are preferable. For example, the He II and Fe XV bands cannot be used on EIT due to the lower mirror reflectivities in those bandpasses. This emphasizes the need for simultaneous support by all coronal imaging instruments and by at least one of the spectrographs, as there will probably be no second chance. A slower cadence implies a longer time before buffer saturation.