Potential Remote-Sensing Technique for Thermospheric Temperature with Ground-Based Resonant Atomic Oxygen Raman Lidar

摘要

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 (exp-3)P(sub-2)(exp-3)P(sub- 1) multiplet level of the ground electronic state of atomic oxygen in the atmosphere to the electronically excited (xp-1)D(sub-2) state and the back- scattered photons at 636.3776 (630.0304) nm, while the atom transitions to (exp-3)P(sub-1)(exp-3)P(sub-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 (exp-1)D(sub-2) remains relaxed primarily by collisions with N(sub-2) and O(sub-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 (exp-1)D(sub-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 (exp-1)D(sub-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 (exp-3)P(sub-2) and (exp-3)P multiplet levels of the ground electronic state of atomic oxygen.