SCEAUX (92) 10.11.2013

On 10 November 2013, a witness at the Parc de Sceaux (92) noticed a light too intense to look at directly. The source gives a time window of 16:59–17:00 but says it was observed for 10 minutes, an unresolved mismatch. After photographing the park, the witness noticed an unexplained white, then red, luminous streak above the horizon in the images. GEIPAN considered a sunset-related phenomenon. Its separation from the Sun was about 22°, characteristic of a parhelion or sundog; the source refers to parhelion information. Such effects form in high-altitude ice clouds. Cirrus in the sky and a cold, dry weather report made that plausible. A sundog could also form in an aircraft contrail, with the observed shape and heavy air traffic supporting that possible origin. GEIPAN classified the case A: parhelion. Green spots in the images were separately identified as internal lens reflections, or lens flare.