Intense Hard X-Ray Emissions in C-class Flares: A Statistical Study with ASO-S/HXI Data

作者：Changxue Chen, Yang Su, W. Chen, J. P. Li, Fu Yu, Weiqun Gan · 发表于：The Astrophysical Journal Letters · 年份：2025 · DOI：10.3847/2041-8213/addf2f · 被引用次数：4 · 研究领域：Solar and Space Plasma Dynamics、Astro and Planetary Science、Stellar, planetary, and galactic studies

Abstract In the standard model of solar eruptive events, coronal mass ejections (CMEs) and flares are associated with each other through magnetic reconnection initiated by erupting flux ropes. Observations also reveal an increasing association ratio between flares and CMEs with flare intensity. However, the fundamental relationship between flares and CMEs, and that between thermal and nonthermal processes, remains unknown. Here we investigate energetic C-class flares (ECFs)—Geostationary Operational Environmental Satellite (GOES) C-class flares with hard X-ray (HXR) emissions above 30 keV—using observations from Advanced Space-based Solar Observatory/Hard X-ray Imager (HXI), Solar Dynamic Observatory, and GOES. Among 1331 C-class flares detected by HXI, 127 ECFs (9.5%) were identified for statistical analysis of their properties and associations with CMEs and other flare-related features. Our statistical results reveal that ECFs have relatively shorter durations and harder spectra (the mean electron power-law index is 4.65), with no significant correlation between soft X-ray flux and nonthermal parameters (e.g., HXR peak flux). Among the 127 events, 53 (42%) were associated with type III bursts, 38 (30%) with jets, at least 13 (∼11%) with 360 nm brightenings, and only 5 (∼4%) with CMEs. Crucially, all five CME events were narrow CMEs associated with jets. The surprising weak correlation between these ECFs and CMEs suggests that noneruptive or confined magnetic field configura...