The Mysterious Red Sky on 6 December 2002

F. Sigernes 1, D.A. Lorentzen 1, N. Lloyd 2, R. Neuber 3, U.-P. Hoppe 4
D. Degenstein 2, N. Shumilov 1,5,10, J. Moen 1,6, Y. Gjessing 1,7, O. Havnes 1,5,
A. Skartveit 7, E. Raustein 7, J. B. Ørbæk 8, and C.S. Deehr 9 

1 The University Centre in Svalbard (UNIS), N-9171 Longyearbyen, Norway
2 ISAS, University of Saskatchewan, Saskatoon, Canada
3 Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany

4 Norwegian Defence Research Establishment, Kjeller, Norway
5 The Auroral Observatory, University of Tromsø, Norway
6 Department of Physics, University of Oslo, Oslo, Norway
7 Geophysical Institute, University of Bergen, Bergen, Norway
8 The Norwegian Polar Institute, Longyearbyen, Svalbard, Norway
9
Geophysical Institute, University of Alaska, Fairbanks, USA  
10 Deceased.

Abstract. 
On the 6th of December 2002, during the polar night, an extraordinary event occured in the sky as viewed from Longyearbyen (78N, 15E), Svalbard, Norway. At 07:30 UT the South - East sky was surprisingly lit up in a deep red color. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was even observed from zenith. The event died out at about 12:30 UT. Spectral measurements from the Auroral Station in Adventdalen confirm that the light source of the event is the Sun. Even though the Sun was between 15 and 11 degrees below the horizon during the event, the measured intensities 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 is scattered solar light from a target below the horizon. This is also confirmed by the OSIRIS instrument onboard the Odin satellite. The deduced height profile indicate that the scattering target is located 20-25 km up in the Stratosphere at a latitude close to 73 - 75 N, South - East of Longyearbyen. The temperatures in this region was 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 Koldeway Station in Ny-Ålesund (79N, 12E) and at ALOMAR close to Andenes (70N, 16E). The event is most likely caused by Twilight Illuminated Polar Stratospheric Clouds (TIPSC) that scatters light towards Svalbard.