Yuannong Zhang

Ionosonde observations of daytime spread F at low latitudes

Spread F on ionograms has been considered to be a phenomenon mainly occurred at nighttime. This study presented a case study of daytime spread F observed by the ionosonde installed at Puer (PUR; 22.7°N, 101.05°E; dip latitude 12.9°N), where daytime spread F that lasted for more than 2 h (about 08:30 LT~10:45 LT) was observed on 14 November 2015. To investigate the possible mechanism, ionograms recorded at PUR and Chiang Mai (18.76°N, 98.93°E; dip latitude 9.04°N) were used in this study. We found that traveling ionospheric disturbances were observed before the occurrence of daytime spread F. Meanwhile, the movement of the peak height of the ionosphere was downward. We suggested that downward vertical neutral winds excited by traveling atmospheric disturbances/atmospheric gravity waves might play a significant role in forming daytime spread F over PUR during geomagnetic storms.

The hardware design of a new ionospheric sounding system

The ionospheric sounding system is a type of high-frequency over-the-horizon skywave radar developed for ionospheric research and HF channel management. The hardware system of a portable low-power multifunctional ionospheric sounding system is presented in this paper. The device can be used for typical ionospheric sounding and spectrum monitoring at monostatic and bistatic station. The system structure and the primary module are depicted in detail. Typical experimental results demonstrate that the design of this device is successful for ionospheric researching.

Modeling radiation belt dynamics using a 3‐D layer method code

A new 3D diffusion code using a recently published layer method has been developed to analyze radiation belt electron dynamics. The code guarantees the positivity of the solution even when mixed diffusion terms are included. Unlike most of previous codes, our 3D code is developed directly in equatorial pitch angle (α0), momentum (p), and L-shell coordinates; this eliminates the need to transform back and forth between (α0,p) coordinates and adiabatic invariant coordinates. Using (α0,p,L) is also convenient for direct comparison with satellite data. The new code has been validated by various numerical tests, and we apply the 3D code to model the rapid electron flux enhancement following the geomagnetic storm on March 17, 2013, which is one of the GEM Focus Group challenge events. An event-specific global chorus wave model, an AL-dependent statistical plasmaspheric hiss wave model, and a recently published radial diffusion coefficient formula from Time History of Events and Macroscale Interactions during Substorms (THEMIS) statistics are used. The simulation results show good agreement with satellite observations in general, supporting the scenario that the rapid enhancement of radiation belt electron flux for this event results from an increased level of the seed population by radial diffusion, with subsequent acceleration by chorus waves. Our results prove that the layer method can be readily used to model global radiation belt dynamics in three dimensions.

A statistical study of inertia gravity waves in the troposphere based on the measurements of Wuhan Atmosphere Radio Exploration (WARE) radar

Wuhan atmosphere radio exploration (WARE) radar is the first mesosphere-stratosphere-troposphere radar to have become operative in the mainland of China and is dedicated to real-time atmospheric observations. Based on the WARE radar data collected for the period from September 2011 to February 2013, 2666 downward and 1735 upward inertia gravity waves (IGWs) are identified from three-dimensional (3-D) wind fields observed in the troposphere and subsequently analyzed in a statistical manner. Wave characteristics including intrinsic frequencies, vertical wavelengths, horizontal wavelengths, vertical wave number spectra, energy density spectra, and wave sources are investigated using a combination of the Lomb-Scargle spectral analysis, the quasi-monochromatic gravity waves model, and the hodograph method. Our results demonstrate that the characteristic parameters of upward and downward tropospheric IGWs are not significantly different. These results indicate that the tropospheric IGWs parameters are not directly correlated with propagation directions. Combining with the information of statistical 3-D wind field and some climatic characteristics of Hubei Province, atmospheric moist convection will contribute most in summer, whereas jet/front systems will contribute most in winter. One may expect seasonal variations to be tied to the varying importance of these sources.

The design and implementation of MST radar at Wuhan, China

The basic configuration of the Wuhan MST (Mesosphere-Stratosphere-Troposphere) radar, which is currently designed and constructed by School of Electronic Information, Wuhan University, is preliminarily described in this paper. The Wuhan MST radar operates at VHF band preoccupied with the real-time characteristics of turbulence and wind field vector in the height range 1–100km with a high temporal and spatial resolution. The extensive feature of Wuhan MST radar points to the feasibility of low thermosphere if desired. This all solid state, all coherent pulse Doppler radar is the Chinas first independently development of MST radar focusing at atmospheric observation. The primary subsystems of the Wuhan MST radar include antenna system, feeder line system, all solid state radar transmitters, digital receivers, beam control system, signal processing system, data processing system, product generating system and user terminal. Advanced radar technologies are used, including high reliability all solid state transmitters, low noise large dynamic range digital receivers, active phased array, high speed digital signal processing and real-time graphic terminals.

Comparisons of ionospheric electron density distributions reconstructed by GPS computerized tomography, backscatter ionograms, and vertical ionograms

Global Positioning System (GPS) computerized ionosphere tomography (CIT) and ionospheric sky wave ground backscatter radar are both capable of measuring the large-scale, two-dimensional (2-D) distributions of ionospheric electron density (IED). Here we report the spatial and temporal electron density results obtained by GPS CIT and backscatter ionogram (BSI) inversion for three individual experiments. Both the GPS CIT and BSI inversion techniques demonstrate the capability and the consistency of reconstructing large-scale IED distributions. To validate the results, electron density profiles obtained from GPS CIT and BSI inversion are quantitatively compared to the vertical ionosonde data, which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings. Our study can improve current understanding of the capability and insufficiency of these two methods on the large-scale IED reconstruction.

Latitudinal variation of the specific local time of postmidnight enhancement peaks in F layer electron density at low latitudes: A case study

Ionospheric nighttime enhancements are manifested in an increase of the electron density at nighttime. This paper studies the latitudinal variation of the specific local time of postmidnight enhancement peaks using ionosondes distributed at low latitudes. To obtain the parameters of the ionosphere, we manually extracted ionograms recorded by ionosondes. Cases show that there are significant latitudinal variations in the observed local time of the postmidnight enhancement peaks. Results show that the lower the geomagnetic latitude, the earlier the enhancement peak occurred in the geomagnetic northern hemisphere. Additionally, the enhancement peaks occurred earlier in the geomagnetic southern hemisphere than that in the geomagnetic northern hemisphere for these present cases. We suggest that the combined effect of the geomagnetic inclination and transequatorial meridional wind might be the main driving force for latitudinal variation of the local time of the occurrence.

A new type Multi-Function Ionospheric Sounding System

This paper introduces a new type Multi-Function Ionospheric Sounding System (MFISS), which bases on the PXI bus. The capabilities of ionospheric vertical sounding, ionospheric oblique sounding and ionospheric oblique backscattering sounding were integrated in a single MFISS, it overcomes the disadvantages of the original ionospheric sounding equipments which have the feature with less function, limited coverage, less obtaining parameters, it also can achieve the function of acquiring the omnibearing geophysical characteristics, the ionosphere channel propagation characteristics and the radio environment characteristics. In this article, firstly, the system structure and the flow of signal processing were introduced, then some typical sounding results acquired by different detection modes were displayed. The sounding results indicate that the system is equipped to handle fast and has a high degree of software features, so for Engineering applications. it is of great significance for the development of ionospheric detection technology and the study of High Frequency(HF) channel characteristic.

MicroRNA-3064-3p regulates the differentiation of cementoblasts through targeting DKK1

BACKGROUND AND OBJECTIVE MicroRNAs (miRNAs) are short, noncoding RNAs that interfere with translation of target mRNAs and thereby play a pivotal role in a variety of biological processes. Cementoblasts are the cells that build up cementum. They share a similar gene expression pattern with osteoblasts. Recent studies have suggested that miRNAs are able to control osteoblast-mediated bone formation. However, the effects of miRNA on cementoblast differentiation still remain unsolved. Herein, we wanted to elucidate the role of miR-3064-3p in cementoblast differentiation. MATERIAL AND METHODS A miRNA microarray was operated to explore the miRNA expression patterns during cementoblast differentiation. miR-3064-3p agomir/antagomir was used to promote or inhibit, respectively, the expression of miR-3064-3p. In order to measure the differentiation level of cementoblasts, quantitative RT-PCR (qRT-PCR), Alizarin red staining, and assessment of alkaline phosphatase activity were performed. Luciferase assays, qRT-PCR, and western blotting were used to identify the target gene of miR-3064-3p. RESULTS miR-3064-3p showed persistently decreased expression during cementoblast differentiation. Overexpression of miR-3064-3p suppressed cementoblast differentiation, while inhibition of miR-3064-3p promoted cementoblast differentiation. Target prediction-analysis tools and dual-luciferase assay identified Dickkopf WNT signaling pathway inhibitor 1 (DKK1) as a direct target of miR-3064-3p. Results from qRT-PCR and western blotting showed that inhibition of miR-3064-3p led to a remarkable increase in DKK1/Dickkopf related protein 1 (Dkk-1) expression. In addition, pretreatment with recombinant Dickkopf related protein 1 (Dkk-1) rescued the miR-3064-3p-mediated suppression of cementoblast differentiation. CONCLUSION This study demonstrates, for the first time, that miR-3064-3p suppresses cementoblast differentiation via the regulation of DKK1.

Equatorial and low‐latitude ionospheric response to the 17–18 March 2015 great storm over Southeast Asia longitude sector

This study mainly investigates equatorial and low-latitude ionospheric response to a great geomagnetic storm occurred on the 17 March 2015. We found that there were some interesting ionospheric phenomena, e.g. short-term ionospheric positive effect, daytime spread F, and morning Equatorial Ionization Anomaly (EIA) in the topside ionosphere, emerged at equatorial and low-latitude region along the longitude of about 100oE. Ground-based ionosondes and in situ satellite (Swarm) were utilized to study the possible mechanisms for these ionospheric phenomena. We found that vertical downward transport of plasma or neutral induced by traveling ionospheric disturbances (TIDs) or traveling atmospheric disturbances (TADs) might make a contribution to the short-term ionospheric positive effect at the main stage of this great storm. Additionally, results suggested that the occurrence of daytime spread F at low latitudes might be due to the diffusion of equatorial ionospheric irregularities in the topside ionosphere along geomagnetic field lines. Moreover, observational evidence shows that TIDs also might be the main driver for morning EIA-like feature recorded by Swarm B satellite in the topside ionosphere. These ionospheric phenomena mentioned above could make us to gain a better understanding of ionospheric storm effects at equatorial and low-latitude region.