Morphology and Density Structure of Post-CME
ZAGREB UNIV (CROATIA) FACULTY OF GEODESY
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Eruption of a coronal mass ejection CME drags and opens the coronal magnetic field, presumably leading to the formation of a large-scale current sheet and the field relaxation by magnetic reconnection. Aims. We analyze physical characteristics of ray-like coronal features formed in the aftermath of CMEs, to check if the interpretation of this phenomenon in terms of reconnecting current sheet is consistent with the observations. Methods. The study is focused on measurements of the ray width, density excess, and coronal velocity field as a function of the radial distance. Results. The morphology of rays indicates that they occur as a consequence of Petschek- like reconnection in the large scale current sheet formed in the wake of CME. The hypothesis is supported by the flow pattern, often showing outflows along the ray and sometimes also inflows into the ray. The inferred inflow velocities range from 3 to 30 kmsexp 1, consistent with the narrow opening-angle of rays, adding up to a few degrees. The density of rays is an order of magnitude larger than in the ambient corona. The density-excess measurements are compared with the results of the analytical model in which the Petschek-like reconnection geometry is applied to the vertical current sheet taking into account the decrease of the external coronal density and magnetic field with height.