Large-scale disturbances preceding a fast halo CME

Abstract

Aims. The nature of coronal waves, often termed “EIT waves” is still unclear. Therefore new efforts are needed to investigate largescale disturbances during solar eruptions. In this paper, we present observations of an event occurring on 19 January 2005, and study the large-scale disturbance during the event in detail. Methods. Using the high cadence images from SXI onboard GOES-12, the large-scale disturbance is identified. Combined with EIT 195 A images, TRACE UV 1600 A images, RHESSI hard X-ray data and MDI/SOHO longitudinal magnetic field maps, the intrinsic process of the large-scale disturbance is discussed. Results. The large-scale disturbance propagated over a distance about 3.8 × 10 5 km at a velocity of about 390 km s −1 . Along the trajectory of the disturbance, a brightening line was left behind, which was coincident with the dense structure in EIT intensity images. With the morphology and metric radio spectrum data, it was found that the disturbance was not a wave but the low-coronal signatures of the eruption.