Abstract:
The outer atmosphere of the sun – called the corona – has been observed during total solar eclipse
for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past,
space-based instruments have permitted us to study the corona uninterruptedly. In spite of these
developments, the dynamic corona and its high temperature (1–2 million K) are yet to be fully
understood. It is conjectured that their dynamic nature and associated energetic events are possible
reasons behind the high temperature. In order to study these in detail, a visible emission line space
solar coronagraph is being proposed as a payload under the small-satellite programme of the
Indian Space Research Organisation. The satellite is named as Aditya-1 and the scientific objectives
of this payload are to study: (i) the existence of intensity oscillations for the study of wavedriven
coronal heating; (ii) the dynamics and formation of coronal loops and temperature structure
of the coronal features; (iii) the origin, cause and acceleration of coronal mass ejections (CMEs)
and other solar active features, and (iv) coronal magnetic field topology and three-dimensional
structures of CMEs using polarization information. The uniqueness of this payload compared to
previously flown space instruments is as follows: (a) observations in the visible wavelength closer
to the disk (down to 1.05 solar radii); (b) high time cadence capability (better than two-images per
second), and (c) simultaneous observations of at least two spectral windows all the time and three
spectral windows for short durations.
