Enhanced Nonthermal Line Broadening inside Coronal Cavities above Solar Prominences Revealed by Spectral Imaging CoronaGraph

Abstract Coronal cavities, often associated with prominences, are crucial structures in understanding coronal heating and the eruption mechanism of coronal mass ejections. Previous studies have identified their lower density, higher temperature, and flux-rope structures. However, spectroscopic observations are still relatively scarce. In this study, we utilize the newly developed Spectral Imaging Coronagraph (SICG), Chinese H α Solar Explorer, and Atmospheric Imaging Assembly (AIA) Solar Dynamics Observatory to analyze the morphology, temperature, Doppler shift, and nonthermal velocity of two coronal cavities observed on 2024 November 13. We find that coronal cavities are distinctly visible in SICG Fe xiv 5303 Å and AIA 193 Å, whereas they are nearly absent in SICG Fe x 6374 Å and AIA 171 Å. The spectroscopic measurements show that the two coronal cavities display asymmetric, ringlike structures in the Fe xiv 5303 Å Doppler shift maps. The nonthermal velocities inside coronal cavities are significantly higher than those of the surrounding streamer areas. In addition, the core regions of coronal cavities, located directly above the prominences, exhibit the highest nonthermal velocities and Doppler velocities. Our results suggest the presence of waves and turbulence in coronal cavities, which are likely more intense than those in the adjacent streamer regions. We suggest that the interaction and exchange between the cold, dense prominence materials and the hot, low-density coronal materials are the main drivers of the waves and turbulence inside coronal cavities.