The detection of 3 & 5 min period oscillations in coronal loops

High cadence, 171 Angstrom, TRACE observations show that outward propagating intensity disturbances are a common feature in large, quiescent coronal loops. These oscillations are interpreted as propagating slow magneto-acoustic waves. Using a wavelet analysis, we found periods of the order of 282 +/- 93 s. However, a careful study of the location of the footpoints revealed a distinct separation between those loops that support oscillations with periods smaller than 200 s and periods larger than 200 s. It was found that loops that are situated above sunspot regions display intensity oscillations with a period of the order of 172 +/- 32 s, whereas oscillations in non-sunspot loops show periods of the order of 321 +/- 74 s. We conclude that the observed longitudinal oscillations are not are-driven but are most likely caused by an underlying driver exciting the loop footpoints. This result suggests that the underlying oscillations can propagate through the transition region and into the corona.