ABSTRACT
We present both modeled capabilities of and experimental data from a Doppler lidar for the stratosphere and the lower mesosphere that uses the edge of a molecular iodine filter in a differential measurement to provide frequency discrimination. Modeled results show a capability for wind measurements to an altitude of 55 km with 1.5-km resolution in 30 min. Experimentally, wind-vector components from 18 to 45 km are measured every 20 min. The molecular-vapor filter provides great advantages with regard to system stability, operation in less-than-optimum weather conditions, and simplicity of data analysis.
ABSTRACT
High-power electromagnetic waves beamed into the ionosphere from ground-based transmitters illuminate the night sky with enhanced airglow. The recent development of a new intensified, charge coupled-device imager made it possible to record optical emissions during ionospheric heating. Clouds of enhanced airglow are associated with large-scale plasma density cavities that are generated by the heater beam. Trapping and focusing of electromagnetic waves in these cavities produces accelerated electrons that collisionally excite oxygen atoms, which emit light at visible wavelengths. Convection of plasma across magnetic field lines is the primary source for horizontal motion of the cavities and the airglow enhancements. During ionospheric heating experiments, quasi-cyclic formation, convection, dissipation and reappearance of the cavites comprise a major source of long-term variability in plasma densities during ionospheric heating experiments.
