Relationship between chromospheric evaporation and magnetic field topology in M-class solar flare

TL;DR

This study investigates the timing and magnetic topology of chromospheric evaporation during an M-class solar flare, revealing delays in plasma flows and their connection to magnetic field structures, enhancing understanding of flare energetics.

Contribution

It provides a detailed analysis linking chromospheric evaporation delays to magnetic field topology and flux rope structures during a solar flare, using multi-wavelength observations.

Findings

Blueshift of hot plasma is delayed by about 1 minute relative to cold plasma.

Delay regions are connected to magnetic polarity inversion lines and flux ropes.

Magnetic field geometry influences the timing and location of evaporation.

Abstract

Chromospheric evaporation is observed as Doppler blueshift during solar flares. It plays one of key roles in dynamics and energetics of solar flares, however, its mechanism is still unknown. In this paper we present a detailed analysis of spatially-resolved multi-wavelength observations of chromospheric evaporation during an M 1.0 class solar flare (SOL2014-06-12T21:12) using data from the NASA's IRIS (Interface Region Imaging Spectrograph) and HMI/SDO (Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory) telescopes, and VIS/NST (Visible Imaging Spectrometer at New Solar Telescope) high-resolution observations, covering the temperature range from 10^4 K to 10^7 K. The results show that the averaged over the region Fe XXI blueshift of the hot evaporating plasma is delayed relative to the C II redshift of the relatively cold chromospheric plasma by about 1 min. The spatial distribution of the delays is not uniform across the region and can be as long as 2 min in several zones. Using vector magnetograms from HMI we reconstruct the magnetic field topology and the quasi-separatrix layer (QSL) and find that the blueshift delay regions as well as the H-alpha flare ribbons are connected to the region of magnetic polarity inversion line (PIL) and an expanding flux rope via a system of low-lying loop arcades with height < ~4.5 Mm. This allows us to propose an interpretation of the chromospheric evaporation based on the geometry of local magnetic fields, and the primary energy source associated with the PIL.