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

Abstract 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.