Imaging evidence for solar wind outflows originating from a CME footpoint

TL;DR

This study provides the first imaging evidence of plasma outflows from a coronal dimming region during a solar eruption, linking these outflows to CME-induced solar wind and magnetic reconnection processes.

Contribution

It offers novel imaging observations of plasma outflows from a dimming region, connecting them to CME activity and magnetic reconnection theories.

Findings

Outflows observed in AIA channels with velocities 70-140 km/s.

Outflows similar to those in coronal holes, indicating solar wind origin.

Magnetic reconnection at filament footpoints during dimming formation.

Abstract

We report on the Atmospheric Imaging Assembly (AIA) observations of plasma outflows originating in a coronal dimming during the 2015 April 28th filament eruption. After the filament started to erupt, two flare ribbons formed, one of which had a well-visible hook enclosing a core (twin) dimming region. Along multiple funnels located in this dimming, a motion of plasma directed outwards started to be visible in the 171 and 193 filter channels of the instrument. In time-distance diagrams, this motion generated a strip-like pattern, which lasted for more than five hours and which characteristics did not change along the funnel. We therefore suggest the motion to be a signature of outflows corresponding to velocities ranging between $\approx70$ and 140 km s$^{-1}$. Interestingly, the pattern of the outflows as well as their velocities were found to be similar to those we observed in a neighboring ordinary coronal hole. Therefore, the outflows were most likely a signature of a CME-induced slow solar wind flowing along the open-field structures rooted in the dimming region. Further, the evolution of the hook encircling the dimming region was examined in the context of the latest predictions imposed for the three-dimensional magnetic reconnection. The observations indicate that the filament's footpoints were, during their transformation to the dimming region, reconnecting with surrounding canopies. To our knowledge, our observations present the first imaging evidence for outflows of plasma from a dimming region.