Sun-as-a-star Analysis of the Solar Eruption Source Region Using Ha Spectroscopic Observations of CHASE

TL;DR

This study analyzes Sun-as-a-star H-alpha spectral data from CHASE to identify signatures of different solar eruptions, revealing spectral features associated with filaments, flares, and CMEs, and discussing implications for stellar CME detection.

Contribution

It provides a detailed spectroscopic analysis of solar eruption regions using CHASE data, highlighting spectral signatures linked to CMEs and flare processes, and explaining challenges in detecting stellar CMEs.

Findings

Filament eruptions show emission with blueshifted/redshifted absorption.

Flare ribbons exhibit line center emission with red asymmetry.

A spectral signature associated with CMEs involves blueshifted absorption without deceleration.

Abstract

Sun-as-a-star analyses serve as a bridge for comparative studies on solar and stellar activities. To investigate the typical Sun-as-a-star Ha temporal spectral characteristics in solar eruption source regions, we analyzed five different types of solar eruptions, using spectroscopic data from the Chinese Ha Solar Explorer (CHASE). Because the spatially-integral Ha spectrum of source region is mainly contributed by emission from heated plasma in flare ribbons and absorption from cold plasma in evolving filaments, we separately analyze the sub-regions of the source region dominated by different dynamical processes. It is revealed that filament eruptions show emission near Ha line center, accompanied by blueshifted/redshifted absorption, while flare ribbons show Ha line center emission with red asymmetry and line broadening. Moreover, a special spectral signature likely associated with coronal mass ejections (CMEs) is identified: prominent blueshifted absorption without a clear deceleration phase, along with redshifted absorption, which can be used as a probe when searching stellar CMEs. Furthermore, in the X9.0 flare (SOL2024-10-03T12:18) accompanied by a violent CME, the expected blueshifted signal is not visible in the spatially-integral Ha spectra. This suggests that filament-lifting signals associated with CMEs in the source region can be obscured by the simultaneous dominant flare-ribbon emission within the integration region, which may explain the relatively small number of confirmed stellar CMEs observed in Ha. We also find that comparison between the Ha and UV spectral observations can effectively reveal the velocity evolution of erupting filaments and potential existence of associated CMEs.