A potential remote-sensing technique for thermospheric temperature with ground-based resonant atomic oxygen Raman lidar

Abstract

We propose a remote-sensing technique to measure temperature in the lower thermosphere with a resonant Raman lidar. A ground-based pulsed laser operating at 630.0304 (636.3776) nm excites 3P 2 ( 3P 1) multiplet level of the ground electronic state of atomic oxygen in the atmosphere to the electronically excited 1D 2 state and the back-scattered photons at 636.3776 (630.0304) nm, while the atom transitions to 3P 1 ( 3P 2), are detected. Using the backscattering Raman cross sections calculated here we show: (1) For the range of altitudes in the lower thermosphere where the fine-structure multiplets of atomic oxygen are in thermodynamic equilibrium with the local translational temperature (LTE) and the electronically excited intermediate state 1D 2 remains relaxed primarily by collisions with N 2 and O 2, the ratio of the backscattered signal can be used to obtain temperature. (2) Higher up, for the range of altitudes where the fine-structure multiplets of atomic oxygen are in LTE and the electronically excited intermediate state 1D 2 is relaxed primarily by spontaneous emission of a photon, the Stokes and anti-Stokes backscattered signal can be used to obtain the atomic oxygen density and local temperature. (3) Still higher up, for the range of altitudes where the fine-structure multiplets of atomic oxygen are not in LTE and the electronically excited intermediate state 1D 2 is relaxed primarily by spontaneous emission of a photon, the Stokes and anti-Stokes backscattered signal can be used to obtain the density of the 3P 2 and 3P 1 multiplet levels of the ground electronic state of atomic oxygen. For a ground-based instrument a simulation with 3 km range gate is used to show that the relative error of temperature measurements from 100 to 250 km could be less than 30%. It is pointed out that this technique has the potential of providing unique data that addresses the modeling of satellite drag and the effects of space weather on the upper atmosphere. In addition, this technique may also permit the detection of the thickness of the temperature inversion layers as well as their temperature and density perturbations.