Extending Counter-Streaming Motion from an Active Region Filament to Sunspot Light Bridge

TL;DR

This study observes counter-streaming motions in an active region filament extending to a sunspot light bridge, revealing complex magnetic and dynamic interactions with implications for solar filament and light bridge behavior.

Contribution

It provides detailed high-resolution analysis of counter-streaming motions and magnetic structures in a filament and light bridge, highlighting their physical differences and connections.

Findings

Counter-streaming motions are observed in the filament and extend into the light bridge.

Filament motions are due to physical mass flow, while light bridge motions are oscillation-driven.

Oscillation power peaks around 4 minutes, indicating wave activity.

Abstract

We analyze the high-resolution observations from the 1.6m telescope at Big Bear Solar Observatory that cover an active region filament. Counter-streaming motions are clearly observed in the filament. The northern end of the counter-streaming motions extends to a light bridge, forming a spectacular circulation pattern around a sunspot, with clockwise motion in the blue wing and counterclockwise motion in the red wing as observed in Halpha off-bands. The apparent speed of the flow is around 10 to 60 km/s in the filament, decreasing to 5 to 20 km/s in the light bridge. The most intriguing results are the magnetic structure and the counter-streaming motions in the light bridge. Similar to those in the filament, magnetic fields show a dominant transverse component in the light bridge. However, the filament is located between opposite magnetic polarities, while the light bridge is between strong fields of the same polarity. We analyze the power of oscillations with the image sequences of constructed Dopplergrams, and find that the filament's counter-streaming motion is due to physical mass motion along fibrils, while the light bridge's counter-streaming motion is due to oscillation in the direction along the line-of-sight. The oscillation power peaks around 4 minutes. However, the section of the light bridge next to the filament also contains a component of the extension of the filament in combination with the oscillation, indicating that some strands of the filament are extended to and rooted in that part of the light bridge.