Revisiting the Spectral Features of Ellerman Bombs and UV Bursts. I. Radiative Hydrodynamic Simulations

TL;DR

This study uses radiative hydrodynamic simulations to clarify how different atmospheric heating layers produce spectral features of Ellerman bombs and UV bursts, revealing their distinct formation heights and spectral signatures.

Contribution

It demonstrates that heating at specific atmospheric layers generates characteristic spectral features of EBs and UV bursts, and shows how combined heating can produce both phenomena simultaneously.

Findings

Heating in the upper photosphere to lower chromosphere produces EB spectral features.

Heating in the mid to upper chromosphere produces UV burst spectral features.

Combined heating sources can reproduce both EB and UV burst features.

Abstract

Ellerman bombs (EBs) and UV bursts are both small-scale solar activities that occur in active regions. They are now believed to form at different heights in the lower atmosphere. In this paper, we use one-dimensional radiative hydrodynamic simulations to calculate various line profiles in response to heating in different atmospheric layers. We confirm that heating in the upper photosphere to the lower chromosphere can generate spectral features of typical EBs, while heating in the mid to upper chromosphere can generate spectral features of typical UV bursts. The intensity evolution of the H$\alpha$ line wing in EBs shows a rise--plateau pattern, while that of the Si IV 1403 \r{A} line center in UV bursts shows a rise--fall pattern. However, the predicted enhancement of FUV continuum near 1400 \r{A} for EBs is rarely reported and requires further observations to check it. With two heating sources or an extended heating source in the atmosphere, both EB and UV burst features could be reproduced simultaneously.