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 foF2, 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 foF2 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 foF2 over SURA in June at that local nighttime period,f0 in these three cases were significantly higher than foF2, 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.
The CSES (China seismic electromagnetic satellite) was launched on February 2, 2018 in a circular polar orbit at an altitude of ~507 km. One of the main objectives of CSES is to search for and characterize ionospheric perturbations that can be associated with seismic activities, to better understand the generation mechanism of such perturbations. Its scientific payload can measure a broad frequency range of electromagnetic waves and some important plasma parameters. This paper is a first-hand study of unusual observations recorded by the CSES over seismic regions prior to four earthquakes with M >7.0 since the satellite's launch. CSES detectors measured irregularities near the epicenter of these four earthquakes. It is already clear that data from instruments onboard the CSES will be of significant help in studies of characteristics of ionospheric perturbations related to earthquakes and their generation mechanisms.