  Cool stars like our Sun are surrounded by a million degree hot outer
atmosphere, the corona. Since more than 60 years the physical nature of the
processes heating the corona to temperatures well in excess of those on the
stellar surface remain puzzling. Recent progress in observational techniques
and numerical modeling now opens a new window to approach this problem. We
present the first coronal emission line spectra synthesized from
three-dimensional numerical models describing the evolution of the dynamics and
energetics as well as of the magnetic field in the corona. In these models the
corona is heated through motions on the stellar surface that lead to a braiding
of magnetic field lines inducing currents which are finally dissipated. These
forward models enable us to synthesize observed properties like (average)
emission line Doppler shifts or emission measures in the outer atmosphere,
which until now have not been understood theoretically, even though many
suggestions have been made in the past. As our model passes these observational
tests, we conclude that the flux braiding mechanism is a prime candidate for
being the dominant heating process of the magnetically closed corona of the Sun
and solar-like stars.
