  Many cool stars possess complex magnetic fields [1] that are considered to
undertake a central role in the structuring and energising of their atmospheres
[2]. Alfv\'enic waves are thought to make a critical contribution to energy
transfer along these magnetic fields, with the potential to heat plasma and
accelerate stellar winds [3] [4] [5]. Despite Alfv\'enic waves having been
identified in the Sun's atmosphere, the nature of the basal wave energy flux is
poorly understood. It is generally assumed that the associated Poynting flux is
generated solely in the photosphere and propagates into the corona, typically
through the continuous buffeting of magnetic fields by turbulent convective
cells [4] [6] [7]. Here we provide evidence that the Sun's internal acoustic
modes also contribute to the basal flux of Alfv\'enic waves, delivering a
spatially ubiquitous input to the coronal energy balance that is sustained over
the solar cycle. Alfv\'enic waves are thus a fundamental feature of the Sun's
corona. Acknowledging that internal acoustic modes have a key role in injecting
additional Poynting flux into the upper atmospheres of Sun-like stars has
potentially significant consequences for the modelling of stellar coronae and
winds.
