Abstract
The discovery of long-period intensity pulsations in coronal loops brings a major constraint for coronal loop heating theories. These EUV pulsations, with periods between 2 and 16 hours, can be found in at least half of the observed active regions, in particular in loops. They are understood to be due to evaporation and condensations cycles, resulting of a quasi-constant and highly-stratified heating. Such thermal cycles have long been predicted by numerical simulations, in which loops are in a state of thermal non-equilibrium. The thermal instability mechanism (runaway cooling and recombination) is thought to be the main driver of the cooling phase of the cycle, which can result in the generation of coronal rain and prominences. During this talk I will present how we detect such pulsations and a detailed thermal characterisation of these events with AIA/SDO. In a second part, I will present a study involving 1D hydrodynamic simulations that are able to reproduce the main characteristics of these events. Moreover, the parameter space study conducted reveals that the occurrence of thermal non-equilibrium (TNE) cycles is sensitive to a combination of the loop geometry and heating parameters (asymmetry and heating power). This naturally explains why these pulsations, remaining during several days, are encountered in some loops but not in all. Moreover, this parameter space study reveals multiple scenarios, in particular in terms of condensation thermodynamics and localisations. These various scenarios need to be further explored. Indeed, the characterisation of TNE cycles is a key step to constraint the frequency and the location of the heating in solar coronal loops.