The fast filament eruption leading to the X-flare on March 29, 2014

TL;DR

This study analyzes a solar filament eruption leading to an X-class flare using high-resolution multi-instrument observations, revealing detailed dynamics and magnetic changes in the eruption process.

Contribution

It provides unprecedented high-resolution observations of the filament eruption and flare, offering new insights into the eruption dynamics and magnetic field changes.

Findings

Filament showed Doppler velocities of 2-5 km/s before eruption

Filament accelerated to at least 600 km/s with an acceleration of 3-5 km/s²

A nearby twisted filament untangled and vanished during the flare

Abstract

We investigate the sequence of events leading to the solar X1 flare SOL2014-03-29T17:48. Because of the unprecedented joint observations of an X-flare with the ground-based Dunn Solar Telescope and the spacecraft IRIS, Hinode, RHESSI, STEREO, and SDO, we can sample many solar layers from the photosphere to the corona. A filament eruption was observed above a region of previous flux emergence, which possibly led to a change in magnetic field configuration, causing the X-flare. This was concluded from the timing and location of the hard X-ray emission, which started to increase slightly less than a minute after the filament accelerated. The filament showed Doppler velocities of $\sim$2-5 km s$^{-1}$ at chromospheric temperatures for at least one hour before the flare occurred, mostly blueshifts, but also redshifts near its footpoints. 15 minutes before the flare, its chromospheric Doppler shifts increased to $\sim$6-10 km s$^{-1}$ and plasma heating could be observed, before it lifted off with at least 600 km s$^{-1}$, as seen in IRIS data. Compared to previous studies, this acceleration ($\sim$3-5 km s$^{-2}$) is very fast, while the velocities are in the common range for coronal mass ejections. An interesting feature was a low-lying twisted second filament near the erupting filament, which did not seem to participate in the eruption. After the flare ribbons started on each of the second filament's sides, it seems to have untangled and vanished during the flare. These observations are some of the highest resolution data of an X-class flare to date and reveal some small-scale features yet to be explained.