Signatures of Reconnection in the Post-CME Rays

Tomislav Zic1, Bojan Vrsnak1, Eugen Vujic2

1Hvar Observatory, Croatia
2Faculty of Science, Department of Physics, Croatia

We analyze physical characteristics of the ray-like coronal features formed in the aftermath of coronal mass ejections (CMEs), using the data recorded by the Large Angle and Spectrometric Coronagraph (LASCO). In particular, we focus on measurements of the ray width, density excess, and flow velocities as a function of the radial distance in the LASCO-C2 field of view. The morphology of rays indicates that they occur as a consequence of the Petschek-like reconnection in the large scale current sheet formed in the wake of CME. The hypothesis is supported by the flow pattern, showing inflows into the ray, and outflows along the ray. The inflow velocities are in the order of 10 km/s, consistent with the narrow opening-angle of rays, adding up to a few degrees. The density of rays is by an order of magnitude larger than in the ambient corona. The mass-excess and 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 that the external coronal density decreases with height. The model-results are consistent with the observations, revealing that the main cause of the density excess in rays is a transport of the dense plasma from lower to larger heights by the reconnection outflow.