Premium
THz limb sounder (TLS) for lower thermospheric wind, oxygen density, and temperature
Author(s) -
Wu Dong L.,
Yee JengHwa,
Schlecht Erich,
Mehdi Imran,
Siles Jose,
Drouin Brian J.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja022314
Subject(s) - terahertz radiation , ionosphere , schottky diode , thermosphere , physics , environmental science , depth sounding , sounding rocket , doppler effect , atmospheric sciences , computational physics , materials science , remote sensing , geophysics , optoelectronics , diode , geology , astronomy , oceanography
Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion‐neutral interactions. We are developing a high‐sensitivity, low‐power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100–140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind‐induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium (LTE) at altitudes up to 350 km. This LTE property, together with day‐and‐night capability and small line‐of‐sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP) mixers and Schottky‐diode‐based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120–150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.