HR: 0800h
AN: SA11A-0210    [Abstracts]
TI: A Potential Remote Sensing Technique for Thermospheric Temperature with Ground-Based Resonant Atomic Oxygen Raman Lidar
AU: * Sharma, R D
EM: ramesh.sharma@hanscom.af.mil
AF: Air Force Research Laboratory/VSBY, 29 Randolph Road, Hanscom AFB, MA 01731-3010
AU: Dao, P D
EM: phan.dao@hanscom.af.mil
AF: Air Force Research Laboratory/VSBY, 29 Randolph Road, Hanscom AFB, MA 01731-3010
AB: 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 ³P₂~(³P₁) multiplet level of the ground electronic state of atomic oxygen in the atmosphere to the electronically excited ¹D₂ state and the back-scattered photons at 636.3776~(630.0304) nm, while the atom transitions to ³P₁~(³P₂), 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 ¹D₂ is relaxed primarily by collisions with N₂ and O₂, the ratio of the backscattered signals 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 but the electronically excited intermediate state ¹D₂ 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 but the electronically excited intermediate state ¹D₂ 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 ³P₂ and ³P₁ 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 120 to 290 km could be less than 20 %. 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.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0355 Thermosphere: composition and chemistry
DE: 0360 Radiation: transmission and scattering
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005