Preliminary experimental results by the prototype of Sanya Incoherent Scatter Radar

In the past decades,the Incoherent Scatter Radar(ISR)has been demonstrated to be one of the most powerful instruments for ionosphere monitoring.The Institute of Geology and Geophysics at the Chinese Academy of Sciences was founded to build a state-ofthe-art phased-array ISR at Sanya(18.3°N,109.6°E),a low-latitude station on Hainan Island,named the Sanya ISR(SYISR).As a first step,a prototype radar system consisting of eight subarrays(SYISR-8)was built to reduce the technical risk of producing the entire large array.In this work,we have summarized the preliminary experimental results based on the SYISR-8.The amplitude and phase among 256 channels were first calibrated through an embedded internal monitoring network.The mean oscillation of the amplitude and phase after calibration were about 1 dB and 5°,respectively,which met the basic requirements.The beam directivity was confirmed by crossing screen of the International Space Station.The SYISR-8 was further used to detect the tropospheric wind profile and meteors.The derived winds were evaluated by comparison with independent radiosonde and balloon-based GPS measurements.The SYISR-8 was able to observe several typical meteor echoes,such as the meteor head echo,range-spread trail echo,and specular trail echo.These results confirmed the validity and reliability of the SYISR-8 system,thereby reducing the technical risk of producing the entire large array of the SYISR to some extent.

Incoherent scatter radar (ISR) observations of high-frequency enhanced ion and plasma lines induced by X/O mode pumping around the critical altitude

Analysis of Incoherent Scatter Radar(ISR)data collected during an experiment involving alternating O/X mode pumping reveals that the high-frequency enhanced ion line(HFIL)and plasma line(HFPL)did not appear immediately after the onset of pumping,but were delayed by a few seconds.By examining the initial behaviors of the ion line,plasma line,and electron temperature,as well as ionosphere conditions,we find that(1)the HFIL and HFPL were delayed not only in the X mode pumping but also in the O mode pumping and(2)the HFIL was not observed prior to enhancement of the electron temperature.Our analysis suggests that(1)leakage of the X mode to the O mode pumping may not be ignored and(2)spatiotemporal uncertainties and spatiotemporal variations in the profiles of ion mass and electron density may have played important roles in the apparent failure of the Bragg condition to apply;(3)nevertheless,the absence of parametric decay instability(PDI)cannot be ruled out,due to our inability to match conditions caused by the spatiotemporal uncertainties.

Analysis of the joint detection capability of the SMILE satellite and EISCAT-3D radar

The Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)satellite is a small magnetosphere–ionosphere link explorer developed cooperatively between China and Europe.It pioneers the use of X-ray imaging technology to perform large-scale imaging of the Earth’s magnetosheath and polar cusp regions.It uses a high-precision ultraviolet imager to image the overall configuration of the aurora and monitor changes in the source of solar wind in real time,using in situ detection instruments to improve human understanding of the relationship between solar activity and changes in the Earth’s magnetic field.The SMILE satellite is scheduled to launch in 2025.The European Incoherent Scatter Sciences Association(EISCAT)-3D radar is a new generation of European incoherent scatter radar constructed by EISCAT and is the most advanced ground-based ionospheric experimental device in the high-latitude polar region.It has multibeam and multidirectional quasi-real-time three-dimensional(3D)imaging capabilities,continuous monitoring and operation capabilities,and multiple-baseline interferometry capabilities.Joint detection by the SMILE satellite and the EISCAT-3D radar is of great significance for revealing the coupling process of the solar wind–magnetosphere–ionosphere.Therefore,we performed an analysis of the joint detection capability of the SMILE satellite and EISCAT-3D,analyzed the period during which the two can perform joint detection,and defined the key scientific problems that can be solved by joint detection.In addition,we developed Web-based software to search for and visualize the joint detection period of the SMILE satellite and EISCAT-3D radar,which lays the foundation for subsequent joint detection experiments and scientific research.

16-Moment Approximation for Ion Velocity Distribution and its Application in Calculations of Incoherent Scatter Spectra

A sixteen moment approximation based on a bi-Maxwellian that contains the stress tensor and the heat flow vector is applied to describe the ion velocity distribution which influences the incoherent scatter spectra. A discussion is made about the effects on the incoherent scatter spectra caused by different values of the normalized perpendicular drift velocity D, aspect angle Φ between the magnetic field and the line-of-sight direction, and the ratio α of the ion-neutral collision to ion cyclotron frequency. Numerical results show that the shifting and asymmetry of incoherent scatter spectra appear parallel to E × B and E as the normalized perpendicular drift velocity D increases due to the ion drift velocity, the stress tensor and the heat flow vector respectively. However, the spectrum is always typically double-humped Maxwellian parallel to B. The ion velocity distribution is more distorted from the Maxwellian as the aspect angle Φ increases from 0° to 90°, and consequently the incoherent scatter spectra is no longer typically double-humped Maxwellian. Asαincreases, the ion velocity distribution becomes Maxwellian and the incoherent scatter spectra become typically double-humped Maxwellian even with a large value of the normalized perpendicular drift velocity D. It is reasonable to use the sixteen-moment approximation to describe the non-Maxwellian plasma characterized by the large temperature anisotropy.

The capabilities of the EISCAT Svalbard Radar for inter-hemispheric coordinated studies

In this article we want to present the EISCAT Svalbard Radar (ESR) in some detail, as well as some of the instruments of interest for ionospheric and magnetospheric research that are located in the vicinity of it. We particularly describe how this instrument cluster, close to the geomagnetic conjugate point of the Chinese Antarctic Zhongshan Station, can contribute to inter hemispheric coordinated studies of the polar ionosphere.

Report on Science Project for Probing the High-Latitude Ionosphere with Complementary Radar and Energetic Neutral Atom(ENA)Measurements

Vast magnetospheric regions are mapped along the field lines to the narrow latitudinal band of the polar/auroral regions. Therefore monitoring of solar wind energy dissipation into the ionosphere at auroral latitudes gives unique opportunities to study geomagnetic disturbances in their complexity from a relatively well-localized vantage point. Here we introduce and present the current state of a recently proposed science project for coordinated monitoring of high-latitude activity with the EISCAT (European Incoherent Scatter) radar array supported by ground-based magnetometer and optical data and ENA (Energetic Neutral Atom) observation from the CINEMA (Cube-Sat for Ions, Neutrals, Electrons and Magnetic field) satellite system.

The nature of electron density enhancement over a wide altitude range during ionosphere heating experiments at EISCAT

During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, whether this enhancement actually corresponds to a true enhancement in electron density remains an open question. When the dispersion relation of ion acoustic waves is followed, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass may have remained unchanged. Furthermore, the solar radio flux and ion drift velocity indicate no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT should not, in fact, be considered a true enhancement.

EISCAT Observations of Main Ionization Troughs in the High-Latitude Ionosphere

F-region electron density depletions associated with main ionization troughs in the high-latitude ionosphere are studied using EISCAT CP3 data of meridian scanning experiments. The troughs in our observations are found to appear mainly in dusk sector, extending from late afternoon to pre-midnight, with higher occurrence rate during equinox and winter. Simultaneous ion drift velocity inF-region shows that the main trough minimum is mostly located at the equator ward edge of the plasma convection flow, rather than in the region where the largest ion flow are observed.