Longitudinal intensity oscillations in coronal loops observed with TRACE - I. Overview of Measured Parameters

In this paper we aim to give a comprehensive overview of geometric and physical properties of longitudinal oscillations in large coronal loops. The 38 examples of propagating disturbances were obtained from the analysis of high cadence, 171 Angstrom TRACE data (JOP 83 and JOP 144). The majority of these outward propagating oscillations are found in the footpoints of large diffuse coronal loop structures, close to active regions. The disturbances travel outward with a propagation speed of the order of v approximate to 122 +/- 43 km s(-1). The variations in intensity are estimated to be roughly 4.1 +/- 1.5% of the background loop brightness. The propagating disturbances are found to be damped very quickly and are typically only detected in the first 8.9 +/- 4.4 Mm along the loop. Using a wavelet analysis, periods of the order of 282 +/- 93 s are found and the energy flux was estimated as 342 +/- 126 erg cm 2 s(-1). We found highly filamentary behavior in the lower part of the coronal loops and showed that the intensity oscillations can be present for several consecutive hours, with a more or less constant period. It is evident that the longitudinal oscillations are a widespread, regularly occurring coronal phenomena. A companion paper is devoted to the interpretation and discussion of the results.