An Abrupt Decrease in Electron Temperature Inside the Ionospheric Density Holes During the Launches of Carrier Rockets

Previous observations have demonstrated that rocket exhaust can trigger ionospheric electron density holes and cause electron temperature enhancements during launches. Using high‐precision measurements from the Sanya incoherent scatter radar, we discovered a previously overlooked decrease in electron temperature. We report a daytime event and a nighttime event. During daytime, the electron temperature first decreased sharply by ∼650 K within 5.5 min, then increased by ∼1000 K before gradually recovering over ∼1 hr. Multi‐beam observations indicated that this cooling was localized near the rocket trajectory, much narrower than the accompanying electron density depletion. Moreover, the ion temperature increased by 550 K. The nighttime electron and ion temperatures decreased by ∼450 and ∼150 K, respectively, without subsequent electron temperature increase. Analysis indicated that these temperature perturbations resulted from the initial expansion cooling following the exhaust injection and the subsequent hole formation, which disrupted the thermal equilibrium in the ionosphere.