|Date:||7.4.2000||Time:||approx. 0 UT||Exposure:||2x about 30s|
|Field:||155o x 70o||Emulsion:||Kodak Royal Gold 1000||Filter:||none|
|Optics:||f=17mm, 1/3.5||Place:||Gross-Schneen, Göttingen||Observer:||T. Credner & E. Vorlaufer|
© Copyright by the Observers
At lower altitudes (up to 110km) the usual green light of wavelength 557.7 nm by excited oxygen dominates. Above, in the altitude range of 200 - 400 km, the excited oxygen glows red. This red emission can't occur at lower altitude since the atmospheric density is too high. For the red emmission the oxygen needs quite a long time to stay in the excited state. But in the dense lower atmosphere the oxygen looses this energy already by encounters with other particles before the red emission might occur.