Abstract
Abstract. On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral measurements from the Auroral Station in Adventdalen confirm that the light was scattered sunlight. Even though the Sun was between 11.8 and 14.6deg below the horizon during the event, the measured intensities of scattered light on the southern horizon from the scanning photometers coincided with the rise and setting of the Sun. Calculations of actual heights, including refraction and atmospheric screening, indicate that the event most likely was scattered solar light from a target below the horizon. This is also confirmed by the OSIRIS instrument on board the Odin satellite. The deduced height profile indicates that the scattering target is located 18–23km up in the stratosphere at a latitude close to 73–75° N, southeast of Longyearbyen. The temperatures in this region were found to be low enough for Polar Stratospheric Clouds (PSC) to be formed. The target was also identified as PSC by the LIDAR systems at the Koldewey Station in Ny-Ålesund (79° N, 12° E). The event was most likely caused by solar illuminated type II Polar Stratospheric Clouds that scattered light towards Svalbard. Two types of scenarios are presented to explain how light is scattered. Keywords. Atmospheric composition and structure (Transmissions and scattering of radiation; Middle atmospherecomposition and chemistry; Instruments and techniques) – History of geophysics (Atmospheric Sciences; The red-sky phenomena)
Highlights
The Auroral Station in Adventdalen, Svalbard (78◦ N, 15◦ E), close to the town of Longyearbyen (LYR), is a multiinstrument platform for studies of dayside aurora and other high latitude optical phenomena
Since the solid Earth shadow was at most 31 km high as seen towards the horizon, that the projection onto the celestial sphere between the solid Earth shadow line and the stations horizontal line of sight is located about 625 km southeast. This means that the target that is illuminated by the sun is close to or below 75◦ North
If we assume the red-sky is due to a lower latitude Polar Stratospheric Clouds (PSC) bathed in sunlight we can immediately calculate that the cloud must between 68◦ N−69◦ N at 27.5◦ E as this is the only location between 20–25 km that sees the sun for the257 h between 7:30 UT and 12:30 UT
Summary
The Auroral Station in Adventdalen, Svalbard (78◦ N, 15◦ E), close to the town of Longyearbyen (LYR), is a multiinstrument platform for studies of dayside aurora and other high latitude optical phenomena. It is more or less completely dark during the day for more than 2 months in the middle of the winter. Near winter solstice the Sun is at least 10 deg below the horizon at noon. It should be almost completely dark in the daytime at Longyearbyen during the months of December and January. Sigernes et al.: Atmospheric studies by optical methods advection from the south led to the observed ground temperatures close to +5 deg Celsius
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
