Fast downflows in a chromospheric filament

TL;DR

This study investigates the chromospheric filament's dynamics using spectropolarimetric data, revealing supersonic downflows and magnetic field variations, enhancing understanding of filament plasma behavior.

Contribution

It introduces a spectropolarimetric analysis of chromospheric filament downflows using Milne-Eddington inversion, highlighting the presence of supersonic velocities and magnetic field measurements.

Findings

Supersonic downflows occur near filament barbs.

Magnetic field strengths are below 200 G in the filament spine.

Fast downflows are associated with magnetic fields between 100-700 G.

Abstract

An active region filament in the upper chromosphere is studied using spectropolarimetric data in He I 10830 A from the GREGOR telescope. A Milne-Eddingon based inversion of the Unno-Rachkovsky equations is used to retrieve the velocity and the magnetic field vector of the region. The plasma velocity reaches supersonic values closer to the feet of the filament barbs and coexist with a slow velocity component. Such supersonic velocities result from the acceleration of the plasma as it drains from the filament spine through the barbs. The line-of-sight magnetic fields have strengths below 200 G in the filament spine and in the filament barbs where fast downflows are located, their strengths range between 100 - 700 G.