A Three-Frequency Ca+ Doppler Lidar for Ion Temperature Measurements in the E and F Regions

The ion temperature is an important parameter for ionospheric detection, yet there is limited research on ion temperatures at altitude range from 80 to 300 km. Currently, a single-frequency Ca⁺ ion optical parametric oscillator (OPO) Lidar system can be used to obtain the Ca⁺ ion density in this region at Yanqing Station, Beijing (40.4°N, 116.0°E). In this study, the ion temperature can be obtained by extending our original lidar to include three-frequency Ca⁺ Doppler detection. This development represents a pioneering step on measuring ion temperatures by lidar in the ionospheric E-F region. Preliminary results in the E region show that lidar temperatures at 90–105 km under the condition of smooth changes in Ca⁺ ion morphology align reasonably with satellite-based observations and model-derived temperatures. Additionally, the exploratory ion temperatures of the F layer peak heights at 200–300 km were obtained. Furthermore, parameter optimization and temperature error analysis in the E-F region are explored, providing valuable insights for the development of Ca⁺ Doppler lidar systems. The advent of Ca⁺ Doppler lidar has greatly expanded the lidar detection altitude range of temperature and the possibilities for in-depth research on ion temperature and velocity in regions affected by complex electrodynamic effects. These findings lay the foundation for subsequent studies of coupling processes in the ionospheric E-F region.