Impulse excitation and damping of slow standing mode oscillations in hot coronal loops

A new theoretical model for the study of slow standing mode oscillations in hot (T > 6 MK) active region coronal loops is presented. These oscillations are observed by the SUMER spectrometer on board the SoHO satellite. The model contains the transition region and the upper chromosphere which enables us to study the entire process of hot loop oscillations - from the impulsive footpoint excitation phase to the rapid damping phase. It is shown that the oscillations can be excited by an impulsive heat deposition due to, e.g., nonlinear Alfvén wave energy deposition or magnetic reconnection at the chromospheric footpoint. The existence of the standing mode oscillations is determined by the duration of the heat deposition. The oscillations are excited most efficiently when the duration of the heat deposition is proportional to the fundamental period of the loop. The amount of released energy determines the oscillation amplitude. The combined effects of thermal conduction and compressive viscosity on the damping time in hot gravitationally stratified loops are much stronger than the effect of chromospheric leakage. The dynamic response of the transition region to the impulsive energy release is examined.