EPP

In June 2018, for the first time, the SURA heating facility in Russia , together with the in-orbit China Seismo-Electromagnetic Satellite (CSES), carried out a series of experiments in emitting high frequency (HF) O-mode radio waves to disturb the ionosphere. This paper reports data from those experiments, collected onboard CSES, including electric field, in-situ plasma parameters, and energetic particle flux. Five cases are analyzed, two cases in local daytime and three in local nighttime. We find that the pumping wave frequencies f₀ in local daytime were close to the critical frequency of the F₂ layer f_oF₂, but no pumping waves were detected by the electric field detector (EFD) on CSES even when the emitted power reached 90 MW, and no obvious plasma disturbances were observed from CSES in those two daytime cases. But on June 16, there existed a spread F phenomena when f₀ was lower than f_oF₂ at that local daytime period. During the three cases in local nighttime, the pumping waves were clearly distinguished in the HF-band electric field at the emitted frequency with the emitted power only 30 MW; the power spectrum density of the electric field was larger by an order of magnitude than the normal background, with the propagating radius exceeding 200 km. Due to the small f_oF₂ over SURA in June at that local nighttime period,f₀ in these three cases were significantly higher than f_oF₂, all belonging to under-dense heating conditions. As for the plasma parameters, only an increase of about 100 K in ion temperature was observed on June 12; in the other two cases (with one orbit without plasma data on June 17), no obvious plasma disturbances were found. This first joint SURA-CSES experiment illustrates that the present orbit of CSES can cross quite close to the SURA facility, which can insure an effective heating time from SURA so that CSES can observe the perturbations at the topside ionosphere excited by SURA in the near region. The detection of plasma disturbances on June 12 with under-dense heating mode in local nighttime provides evidence for likely success of future related experiments between CSES and SURA, or with other HF facilities.

An extraordinary (X-mode) electromagnetic wave, injected into the ionosphere by the ground-based heating facility at Tromsø, Norway, was utilized to modify the ionosphere on November 6, 2017. The high-power high-frequency transmitter facility located at Tromsø belongs to the European Incoherent Scatter Scientific Association. In the experiment, stimulated electromagnetic emission (SEE) spectra were observed. A narrow continuum occurred under cold-start conditions and showed an overshoot effect lasting several seconds. Cascading peaks occurred on both sides of the heating frequency only in the preconditioned ionosphere and also showed an overshoot effect. These SEE features are probably related to the ponderomotive process in the X-mode heating experiment and are helpful for understanding the physical mechanism that generated them during the X-mode heating experiment. The features observed in the X-mode heating experiments are novel and require further investigation.