Affiliation: | 1Instituto Nacional de Pesquisas Espaciais, CP 515, 12245-970, Sao Jose dos Campos, SP, Brazil 2Max-Planck-Institut für Aeronomie, D 37191 Katlenburg-Lindau, Germany 3Instituto de Astronomia y Astrofisica del Espacio, C. Universitaria, 1428 Buenos Aires, Argentina |
Abstract: | In this work we present height-time diagrams of 2 halo coronal mass ejections, observed on September 28th, 1997 and June 29th, 1999. The CMEs were observed by the Large Angle and Spectroscopic Coronagraph (LASCO), which observes the solar corona from 2 to 32 solar radii. To obtain these diagrams we divide the LASCO images of a given sequence in angular slices, transform them into rectangular slices (their width chosen proportional to the time distance to the next image) and place them side by side. Thus, the speed profile of any pattern moving in the particular latitudinal slice can be derived. With this method we were able to identify even minor speed changes in several angular positions for the chosen events. This technique is particularly appropriate to identify acceleration or deceleration of structures in halo CMEs. |