Observations and theory of slow waves in coronal loops

High cadence TRACE observations show that outward propagating intensity disturbances are a common feature in large, quiescent coronal loops, close to active regions. An overview is given of measured parameters of such longitudinal oscillations in coronal loops. The observed oscillations are interpreted as propagating slow magneto-acoustic waves and are unlikely to be flare-driven. A theoretical model of slow magneto-acoustic waves, incorporating the effects of gravitational stratification, the magnetic field geometry, thermal conduction and compressive viscosity is presented to explain the very short observed damping lengths. The results of these numerical simulations are compared with the TRACE observations. Preliminary results indicate that thermal conduction and the magnetic field geometry play an important role.