Emergence of a Helical Flux Rope Under an Active Region Prominence

TL;DR

This study observed the emergence of a helical flux rope beneath an active region prominence, revealing magnetic field evolution that supports prominence stability and evolution.

Contribution

It provides direct observational evidence of a helical flux rope emerging under a prominence, linking magnetic flux emergence to prominence dynamics.

Findings

Helical flux rope was emerging from below the photosphere.

Horizontal magnetic fields changed from normal to inverse polarity.

Horizontal magnetic regions showed blueshift signals.

Abstract

Continuous observations were obtained of active region 10953 with the Solar Optical Telescope (SOT) on board the \emph{Hinode} satellite during 2007 April 28 to May 9. A prominence was located over the polarity inversion line (PIL) in the south-east of the main sunspot. These observations provided us with a time series of vector magnetic fields on the photosphere under the prominence. We found four features: (1) The abutting opposite-polarity regions on the two sides along the PIL first grew laterally in size and then narrowed. (2) These abutting regions contained vertically-weak, but horizontally-strong magnetic fields. (3) The orientations of the horizontal magnetic fields along the PIL on the photosphere gradually changed with time from a normal-polarity configuration to a inverse-polarity one. (4) The horizontal-magnetic field region was blueshifted. These indicate that helical flux rope was emerging from below the photosphere into the corona along the PIL under the pre-existing prominence. We suggest that this supply of a helical magnetic flux into the corona is associated with evolution and maintenance of active-region prominences.