By using a two‐color scheme, we have given a closer scrutiny to the Autler–Townes doublet splitting and ac Stark shift in the 2+2‐photon ionization spectra of CO Ion A ¹(v’=4)←X ¹Σ⁺(v‘=0) transition in the presence of another strong laser field, which is resonant with the transition C ¹Σ⁺(v’=0)←A ¹Π(v’=4)P₁₀ branch. All the observations of ac Stark shift/broadening as a function of the perturbing light frequency and its spatial homogeneity strongly support our previous theoretical interpretation for one‐color studies. A qualitative interpretation based on the dressed state theory, which is being quantified, for the Autler–Townes splitting as well as the ac Stark effect has been given. In particular, the magnitude of the Autler–Townes splitting is found to vary with the square root of the perturbing light intensity, in line with the dressed state theory.

This article presents observational results of the vertical structural evolution of ionospheric holes during two rocket launches. A combination of observations from the newly built Sanya incoherent scatter radar (SYISR) and Global Navigation Satellite System networks was employed. The vertical structural evolution of two rocket‐induced ionospheric holes over the SYISR could be divided into three stages. Firstly, 10–11 min after launch, the holes initially appeared in the topside ionosphere. Then, the holes expanded rapidly toward higher and lower altitudes. At ∼30 min after launch, the holes extended to an altitudinal range of ∼200 km to over 700 km. The maximum depletion altitude was 425 km for the afternoon event and 283 km for the midnight event. Finally, the holes recovered slowly, with faster recovery at higher altitudes. Our work contributes to further understanding the vertical structural evolutionary mechanisms of the ionospheric holes and relevant ionospheric processes.

The radar constant calibration in incoherent scatter radar ion line processing is essential for the data quality and was not paid enough attention in previous studies. In this investigation, based on several experiments made by the newly built Sanya incoherent scatter radar (SYISR), we made and evaluated the ion line calibration by plasma line both in case study and statistically. The calibration factor had local time and altitude variations, due to the corresponding variations of the transmitted power, the radar gain, and the noise temperature. We obtained a mean calibration factor of 1.35 by the simultaneous measured plasma line and ion line electron density and applied it to a one-month ion line observation calibration. Through a co-located ionosonde measured f_oF₂ evaluation, the calibration decreased the mean deviation from −1.92 MHz (−18%) to −0.33 MHz (−3%), which resulted in much better agreement between the ion line f_oF₂ after calibration and the ionosonde results. The existed deviations between after calibration and ionosonde results were due to the uncertainties either in the used calibration factor or the ionosonde measurements. An empirical T_e/T_i usage in raw electron density estimation and ignoring the seasonal and short-term variations of the effecting factors might influence the calibration performance. Using the to-be-completed SYISR Tristatic System, the performance of plasma line calibration technique is expected to be improved in the future.

In this study, we used the Sanya Incoherent Scatter Radar (SYISR) to observe the altitude profiles of traveling ionospheric disturbances (TIDs) during a moderate magnetic storm from 13 to 15 March 2022. Three TIDs were recorded, including two large-scale TIDs (LSTIDs) and one medium-scale TID (MSTID). These LSTIDs occurred during the storm recovery phase, characterized by periods of ~110–155 min, downward phase velocities of 22–60 m/s, and a relative amplitude of 17–25%. A nearly vertical front was noted at ~350–550 km, differing from AGW theory predictions. This structure is more attributed to the combined effects of sunrise-induced electron density changes and pre-sunrise uplift. Moreover, GNSS observations linked this LSTID to high-latitude origins, indicating a connection to polar magnetic storm excitation. However, the second LSTID was observed at lower altitudes (150–360 km) with a higher elevation angle (~17°). This LSTID, observed by the SYISR, was absent in the GNSS data from mainland China and Japan, suggesting a potential local source. The MSTID exhibited a larger relative amplitude of 29–36% at lower altitudes (130–210 km) with severe upward attenuation. The MSTID may be related to atmospheric gravity waves from the lower atmosphere. AGWs are considered to be the perturbation source for this MSTID event.