Temporal evolution of multiple evaporating ribbon sources in a solar flare

TL;DR

This study uses high-resolution IRIS observations to analyze the dynamic evolution of chromospheric evaporation and condensation during an X-class solar flare, revealing consistent impulsive phase behaviors across multiple flare kernels.

Contribution

It provides the first detailed temporal and spatial analysis of individual flare kernels' evolution during the impulsive phase of a major solar flare.

Findings

Coronal upflows reach ~300 km/s in flare kernels.

Chromospheric downflows up to 40 km/s observed.

Flow evolution is consistent with hydrodynamic flare models.

Abstract

We present new results from the Interface Region Imaging Spectrograph showing the dynamic evolution of chromospheric evaporation and condensation in a flare ribbon, with the highest temporal and spatial resolution to date. IRIS observed the entire impulsive phase of the X-class flare SOL2014-09-10T17:45 using a 9.4 second cadence `sit-and-stare' mode. As the ribbon brightened successively at new positions along the slit, a unique impulsive phase evolution was observed for many tens of individual pixels in both coronal and chromospheric lines. Each activation of a new footpoint displays the same initial coronal up-flows of up to ~300 km/s, and chromospheric downflows up to 40 km/s. Although the coronal flows can be delayed by over 1 minute with respect to those in the chromosphere, the temporal evolution of flows is strikingly similar between all pixels, and consistent with predictions from hydrodynamic flare models. Given the large sample of independent footpoints, we conclude that each flaring pixel can be considered a prototypical, `elementary' flare kernel.