Measurement of Density Profile with Step-Swept Microwave Reflectometry

A one-channel microwave reflectometer is used to measure the electron densityprofile in a low-density plasma experiment (n_e < 0.27 x 10^(19) m^(-3)) sustained by 2.45 GHzlower hybrid current drive (LHCD) on TRIAM-1M. In order to remove the effect of phase runawayphenomena, a step-like frequency-sweeping way is used and a special phase analysis technique isintroduced. The density profile is reconstructed in TRIAM-1M with the swept frequency ranged from 6GHz to 15 GHz. The corresponding cutoff density is from (0.045 ～ 0.28) x 10^(19) m^(-3) in theordinary polarization mode. The results are in good agreement with the measurements from amulti-channel 2 mm-wavelength interferometer.

Application of the Magnetic Surface Based PARK-Matrix Method in the HCOOH Laser Interferometry System on HL-2A

A new electron density profile reconstruction procedure based on the PARK-matrix method has been firstly exploited for the multi-chord formic acid（HCOOH, λ=432.5 μm） laser interferometry system on the HL-2A tokamak. According to the geometric coordinates of the magnetic surfaces reconstructed by the CF（current fitting） code and the assumption that the electron density between two adjacent magnetic surfaces is a constant, the local electron density is calculated layer by layer, and the electron density profile n_e（Z） can be determined, as well as the density profile n_e（R）. The simulation result indicates that the error of the PARK-matrix method is acceptable for the four-chord HCOOH laser interferometer. In the applications, it shows that the reconstructed electron density profile agrees well with the microwave reflectometry measurement,and the sawtooth reversion radius is consistent with that deduced from the soft X-ray signals.Meanwhile, the electron density profiles with electron cyclotron resonance heating（ECRH） and supersonic molecular beam injection（SMBI） are also reconstructed and analyzed.

Application of the oblique ionogram as vertical ionogram

The vertical ionogram can provide the important ionospheric parameters, such as critical frequency, virtual height and electron density, for ionospheric research. The oblique ionosonde has the ability to detect the ionosphere over sea and other terrain where it is not practical to deploy vertical sounder and provide more ionograms with less transmitting and receiving devices. Therefore, the conversion of the oblique ionogram to vertical ionogram for obtaining the important ionospheric parameters is a very useful inversion technology. The experimental comparison between oblique and vertical detections was carried out in the equatorial ionospheric anomaly (EIA) region of south China on 25 and 26 August 2010. The oblique detecting path was from Wuhan to Shenzhen and the VI ionosonde was located in the midpoint of the oblique path. The oblique ionogram reversion results showed a small deviation of the critical frequency, minimum virtual height as well as the electron density profile of the ionospheric F layer, as compared with the real vertical observations.

CSES GNSS ionospheric inversion technique, validation and error analysis

With the increased number of low Earth orbit(LEO) satellites equipped with global navigation satellite system(GNSS) receiver,the LEO based GNSS slant total electron content(TEC) and electron density profile(EDP) data play an increasingly important role in space weather and ionospheric research due to improved global coverage. China Seismo-Electromagnetic Satellite(CSES), which was launched in February 2018, is equipped with GNSS receiver for either precise orbit determination(POD) and ionospheric inversion. The purpose of the present paper is to validate CSES GNSS ionospheric inversion technique based on the real observations and verify the accuracy of TEC and EDP retrieval based on the simulated data. The following conclusions can be drawn: the epoch difference inversion(EDI) derived from CSES can successfully retrieve the EDPs without non-occultation side measurements; the technique of EDI and the calibrated TEC inversion(CTI) have similar behaviors in inversion errors,however, the retrieved Nm F2 and hm F2 have a larger systematic error surrounding the equatorial ionization anomaly(EIA)where the assumption of spherical symmetry is often invalid; the precision and accuracy of retrieved TEC have been investigated in the paper based on the simulated data, and it is found that the accuracy of the retrieved TEC is relative to solar activity: the lower the F10.7 index, the higher the accuracy of retrieved TEC.