The Ellerman bomb and Ultraviolet burst triggered successively by an emerging magnetic flux rope

TL;DR

This study uses 3D MHD simulations to explore how an emerging magnetic flux rope triggers successive Ellerman bombs and UV bursts in the solar atmosphere, revealing their formation, heating mechanisms, and altitude differences.

Contribution

It provides the first detailed 3D simulation analysis of the sequential occurrence and distinct heating processes of EBs and UV bursts caused by flux rope emergence.

Findings

EBs appear earlier and last about 80 seconds.

UV bursts occur six minutes after EBs and last about 60 seconds.

EBs are heated by shocks from horizontal flows, UV bursts by magnetic reconnection.

Abstract

Ellerman bombs (EBs) and Ultraviolet (UV) bursts are common brightening phenomena which are usually generated in the low solar atmosphere of emerging flux regions. In this paper, we have investigated the emergence of an initial un-twisted magnetic flux rope based on three-dimensional (3D) magneto-hydrodynamic (MHD) simulations. The EB-like and UV burst-like activities successively appear in the U-shaped part of the undulating magnetic fields triggered by Parker Instability. The EB-like activity starts to appear earlier and lasts for about 80 seconds. Six minutes later, a much hotter UV burst-like event starts to appear and lasts for about 60 seconds. Along the direction vertical to the solar surface, both the EB and UV burst start in the low chromosphere, but the UV burst extends to a higher altitude in the up chromosphere. The regions with apparent temperature increase in the EB and UV burst are both located inside the small twisted flux ropes generated in magnetic reconnection processes, which are consistent with the previous 2D simulations that most hot regions are usually located inside the magnetic islands. However, the twisted flux rope corresponding to the EB is only strongly heated after it floats up to an altitude much higher than the reconnection site during that period. Our analyses show that the EB is heated by the shocks driven by the strong horizontal flows at two sides of the U-shaped magnetic fields. The twisted flux rope corresponding to the UV burst is heated by the driven magnetic reconnection process.