First Observation of the Altitude Distribution of Atomic Potassium Dayglow in the MLT

Abstract:

Cosmic dust enters the mesosphere/lower thermosphere and ablates into a hot gas which later condenses into meteoritic smoke, leaving behind some atomic potassium in the gas phase. In this paper we report the observation of day airglow from atomic K from the RAIDS on ISS and OSIRIS on ODIN satellite instruments. This atomic potassium has also been measured extensively with potassium lidars at several sites. The atomic potassium reacts with ozone to form potassium oxide, KO. The KO reacts with atomic oxygen to recycle the atomic K. This balance between production and loss leads to a dominant concentration of K. The resonance scattering of sunlight by K leads to a chemi-luminescent airglow emission which has been previously noted by the authors, Llewellyn and Evans, from their OSIRIS spectrograph on the ODIN satellite. The intensity of this airglow emission from K is proportional to the product of the atomic K concentration and the resonance scattering coefficient (g-factor). Since the rate of reaction for the reaction of KO with atomic oxygen is also in equilibrium with rate of reaction of K with ozone, the day airglow intensity can be used to derive the ground state K density if the atomic oxygen concentrations are available. The atomic oxygen can be derived from other airglow emissions, particularly the A band of O₂ which is also observed simultaneously by the OSIRIS instrument. The concentration profile of K is derived from the altitude profile of the dayglow emission of potassium at 766.5 nm. The observed volume emission dayglow altitude profile will be compared with model calculations by the authors. The RAIDS ISS profile is peaked at 100 km level and extends up to 160 km. The profile has been simultaneously observed in the 766.5 and the 769.9 nm lines. Since this is the first measurement of the altitude profile of dayglow K emission, it can be compared with extensive historic ground based measurements of K twilight emission taken at Saskatoon in the 60s by Sullivan and Hunten (CJP; 1964 doi10.1139/p64-087).