  The solar corona, the tenuous outer atmosphere of the Sun, is orders of
magnitude hotter than the solar surface. This 'coronal heating problem'
requires the identification of a heat source to balance losses due to thermal
conduction, radiation and (in some locations) convection. The review papers in
this Theo Murphy meeting issue present an overview of recent observational
findings, large- and small-scale numerical modelling of physical processes
occurring in the solar atmosphere and other aspects which may affect our
understanding of the proposed heating mechanisms. At the same time, they also
set out the directions and challenges which must be tackled by future research.
In this brief introduction, we summarize some of the issues and themes which
reoccur throughout this issue.
