Coronal rain: the cool alter ego of the hot solar corona

Coronal heating is a fundamental process of stellar atmospheres. Yet, the main mechanisms behind it are still unclear, mostly due to the short time and spatial scales on which they operate. However, not everything in stellar coronae is hot. The radiative properties of plasmas make them thermally unstable, leading to pervasive, continuous cycles of heating and cooling, which set coronae in a dynamic and strong thermally inhomogeneous state. Relatively to its famous “hot” side, little is known about the corona’s cooler counterpart, despite its ubiquity. Prominences and, particularly, coronal rain, constitute direct observational evidence of this inhomogeneity. The importance of the associated thermal instability is fundamental to explain structure at large interstellar scales, and has been increasingly recognised in recent years for the dynamics of the solar atmosphere. In this talk I will present a brief overview of recent developments in the field from the observational and numerical perspectives, which show that coronal rain offers a unique insight into the coronal heating agents, the local substructure and global topology of the coronal magnetic field, and the chromosphere-corona mass and energy cycle.