Unusual rainbow and white rainbow: A new auroral candidate in oriental historical sources

Abstract

Solar activity has been recorded as auroras or sunspots in various historical sources. These records are of great importance for investigating both long-term solar activities and extremely intense solar flares. According to previous studies, they were recorded as vapor, cloud, or light, especially in oriental historical sources; however, this terminology has not been discussed adequately, and remains still quite vague. In this paper, we suggest the possibility of using unusual rainbow and white rainbow as candidates of historical auroras in oriental historical sources, and examine if this is probable. This discovery will help us to make more comprehensive historical auroral catalogues, and require us to add these terms to auroral candidates in oriental historical sources.