# Velocities of flare kernels and the mapping norm of field line connectivity

## TL;DR

This study analyzes the velocities of flare ribbon kernels during a solar eruption, linking their motion to magnetic field strength and the norm of quasi-separatrix layers, supporting the interpretation of kernel motions as signatures of magnetic reconnection.

## Contribution

The paper introduces a combined observational and modeling approach to connect flare kernel velocities with the norm of QSLs, providing new insights into magnetic reconnection during eruptions.

## Key findings

- Kernel velocities up to 450 km/s observed along flare ribbons.
- Kernel velocities are roughly anti-correlated with magnetic field strength.
- Modelled norm N of QSLs matches the observed kernel dynamics.

## Abstract

We report on observations of flare ribbon kernels during the 2012 August 31 filament eruption. In the 1600\,\AA{} and 304\,\AA{} channels of the Atmospheric Imaging Assembly, flare kernels were observed to move along flare ribbons at velocities $v_\parallel$ of up to $450$ km\,s$^{-1}$. Kernel velocities were found to be roughly anti-correlated with strength of the magnetic field. Apparent slipping motion of flare loops was observed in the 131\,\AA{} only for the slowest kernels moving through strong-$B$ region. In order to interpret the observed relation between $B_{\text{LOS}}$ and $v_\parallel$, we examined distribution of the norm $N$, a quantity closely related to the slippage velocity. We then calculated the norm $N$ of the quasi-separatrix layers (QSLs) in MHD model of a solar eruption adapted to the magnetic environment which qualitatively agrees to that of the observed event. We found that both the modelled $N$ and velocities of kernels reach their highest values in the same weak-field regions, one located in the curved part of the ribbon hook and the other in the straight part of the conjugate ribbon located close to a parasitic polarity. Oppositely, lower values of the kernel velocities are seen at the tip of the ribbon hook, where the modelled $N$ is low. Since the modelled distribution of $N$ matches the observed dynamics of kernels, this supports that the kernel motions can be interpreted as a signature of QSL reconnection during the eruption.