  Since the Lalpha rocket observations of (Gabriel, Solar Phys. 21, 392, 1971),
it has been realized that the hydrogen (H) lines could be observed in the
corona and offer an interesting diagnostic for the temperature, density, and
radial velocity of the coronal plasma. Moreover, various space missions have
been proposed to measure the coronal magnetic and velocity fields through
polarimetry in H lines. A necessary condition for such measurements is to
benefit from a sufficient signal-to-noise ratio. The aim of this article is to
evaluate the emission in three representative lines of H for three different
coronal structures. The computations have been performed with a full non-local
thermodynamic equilibrium (non-LTE) code and its simplified version without
radiative transfer. Since all collisionnal and radiative quantities (including
incident ionizing and exciting radiation) are taken into account, the
ionization is treated exactly. Profiles are presented at two heights (1.05 and
1.9 solar radii, from Sun center) in the corona, and the integrated intensities
are computed at heights up to five solar radii.We compare our results with
previous computations and observations (e.g. Lalpha from UVCS) and find a rough
(model-dependent) agreement. Since the Halpha line is a possible candidate for
ground-based polarimetry, we show that in order to detect its emission in
various coronal structures, it is necessary to use a very narrow (less than 2 A
wide) bandpass filter.
