Prominence Formation Associated with an Emerging Helical Flux Rope

TL;DR

This study uses high-resolution solar observations to analyze the emergence of a helical flux rope and its role in prominence formation, revealing detailed magnetic configurations and flow patterns associated with prominence stability.

Contribution

It provides detailed observational evidence of a helical flux rope emergence and its connection to prominence formation, advancing understanding of solar magnetic structures.

Findings

Helical flux rope emergence observed with specific size (~30,000 km long, 10,000 km wide).

Diverging mesogranular flows along the polarity inversion line are linked to flux emergence.

Reconnection of the flux rope with pre-existing prominence fields stabilizes the prominence for days.

Abstract

The formation and evolution process and magnetic configuration of solar prominences remain unclear. In order to study the formation process of prominences, we examine continuous observations of a prominence in NOAA AR 10953 with the Solar Optical Telescope on the \emph{Hinode} satellite. As reported in our previous Letter, we find a signature suggesting that a helical flux rope emerges from below the photosphere under a pre-existing prominence. Here we investigate more detailed properties and photospheric indications of the emerging helical flux rope, and discuss their relationship to the formation of the prominence. Our main conclusions are: (1) A dark region with absence of strong vertical magnetic fields broadens and then narrows in Ca \textsc{ii} H-line filtergrams. This phenomenon is consistent with the emergence of the helical flux rope as photospheric counterparts. The size of the flux rope is roughly 30,000 km long and 10,000 km wide. The width is larger than that of the prominence. (2) No shear motion or converging flows are detected, but we find diverging flows such as mesogranules along the polarity inversion line. The presence of mesogranules may be related to the emergence of the helical flux rope. (3) The emerging helical flux rope reconnects with magnetic fields of the pre-existing prominence to stabilize the prominence for the next several days. We thus conjecture that prominence coronal magnetic fields emerge in the form of helical flux ropes that contribute to the formation and maintenance of the prominence.