A bright coronal downflow seen in multi-wavelength observations: evidence of a bifurcating flux-rope?

TL;DR

This study analyzes a bright coronal downflow observed after a CME, combining multi-wavelength data to suggest it originated from magnetic reconnection within an erupting flux rope, indicating a bifurcation process.

Contribution

It provides multi-thermal, multi-instrument observations of the downflow, revealing its origin from internal magnetic reconnection and flux rope bifurcation, which was not previously documented in detail.

Findings

Downflow started at about 1.6 solar radii with hot and cold plasma.

Downflow speed exceeded free-fall speed, indicating strong acceleration.

Evidence supports magnetic reconnection inside the flux rope causing bifurcation.

Abstract

Aims: To study the origin and characteristics of a bright coronal downflow seen after a coronal mass ejection associated with erupting prominences on 5 March 2000. Methods: This study extends that of Tripathi et al. (A&A, v. 449, pp. 369) based on the Extreme-ultraviolet Imaging Telescope (EIT), the Soft X-ray Telescope (SXT) and the Large Angle Spectrometric Coronagraph (LASCO) observations. We combined those results with an analysis of the observations taken by the H${\alpha}$ and the Mk4 coronagraphs at the Mauna Loa Solar Observatory (MLSO). The combined data-set spans a broad range of temperature as well as continuous observations from the solar surface out to 30 R$_{\sun}$. Results: The downflow started at around 1.6R$_{\sun}$ and contained both hot and cold gas. The downflow was observed in the H${\alpha}$ and the Mk4 coronagraphs as well as the EIT and the SXT and was approximately co-spatial and co-temporal providing evidence of multi-thermal plasma. The H${\alpha}$ and Mk4 images show cusp-shaped structures close to the location where the downflow started. Mk4 observations reveal that the speed of the downflow in the early phase was substantially higher than the free-fall speed, implying a strong downward acceleration near the height at which the downflow started. Conclusions: The origin of the downflow was likely to have been magnetic reconnection taking place inside the erupting flux rope that led to its bifurcation.