The unusual daytime F-region Field-Aligned Irregularities (FAIs) were observed by the HCOPAR and the satellites at low latitudes on 13 June 2022. These irregularities survived from night-time to the following afternoon at 15:00 LT. During daytime, they appeared as fossil structures with low Doppler velocities and narrow spectral widths. These characteristics indicated that they drifted along the magnetic field lines without apparent zonal velocity to low latitudes. Combining the observations of the ICON satellite and the Hainan Digisonde, we derived the movement trails of these daytime irregularities. We attributed their generation to the rapid ascent of the F-layer due to the fluctuation of IMF Bz during the quiet geomagnetic conditions. Subsequently, the influence of the substorm on the low-latitude ionosphere was investigated and simulated. The substorm caused the intense Joule heating that enhanced the southward neutral winds, carrying the neutral compositional disturbances to low latitudes and resulting in a negative storm effect in Southeast Asia. The negative storm formed a low-density circumstance and slowed the dissipation of the daytime FAIs. These results may provide new insights into the generation of post-midnight irregularities and their relationship with daytime fossil structures.

A new stepwise and radially processed method for synthesizing uniformly distributed circular planar arrays with quantized weights is proposed in this paper. This method is based on a generalized analytical equation describing that for high directivity focusing arrays, minimizing the weighted mean square error between the reference pattern and the synthesized pattern is equivalent to minimizing the mean square error between the radial cumulative distributions of the reference distribution and the synthesized distribution. This principle has been successfully performed for designing large concentric ring arrays, and in this paper, we extend its use for synthesizing uniformly distributed planar circular arrays with quantized weights. Various numerical examples and comparisons with several reported statistical methods in terms of the lowest Maximum SideLobe Level (MSLL) demonstrate the effectiveness of the proposed method.

With the support of the second phase of the Chinese Meridian Project, a new mesosphere-stratosphere-troposphere observation radar (MST radar), called Qinzhou MST radar, located in Qinzhou City, Guangxi Province, China (22°7'55''N,108°16'20''E) is under construction. The Qinzhou MST radar is a large VHF monostatic pulse Doppler radar with an active phased array antenna system, mainly using Doppler beam swinging technique for observation. The capability of multibeam observation, space antenna observation, and frequency- and spatial-domain interferometry are also employed. The main scientific objective of this radar is to explore the atmosphere dynamical processes at low latitudes of China. The observation of ionospheric field-aligned irregularities (FAIs) is also an important function of the radar. The radar applies a circular array composed of 1261 3-element crossed Yagi antennas with a diameter of 153 m and an aperture of near 2×10 ⁴ m ² . Thereinto, 997 elements connect both transmitting and receiving channels and 264 elements distributed near the edge connect only receiving channels. The peak power of the transmitter in each transmitting/receiving (T/R) module is 2 kW. The central frequency and bandwidth of the output signal are 50 and 4 MHz, respectively. The peak power of the whole system will be close to 2 MW. This article presents the initial design of the Qinzhou MST radar, and the construction will be completed at the end of 2022.

The oblique-incidence ionosonde network in North China is a very unique system for regional ionospheric observation. It contains 5 transmitters and 20 receivers, and it has 99 ionospheric observation points between 22.40° N and 33.19° N geomagnetic latitudes. The data of the ionosonde network were used to investigate the statistical characteristics of the quasi-3-h large-scale traveling ionospheric disturbances (LSTIDs). From September 2009 to August 2011, 157 cases of the quiet-time LSTIDs were recorded; 110 cases traveled southward, 46 cases traveled southwestward and only 1 case traveled southeastward. The LSTIDs mainly appeared between 10:00 and 19:00 LT in the months from September to the following May. We compared the data of the Beijing, Mohe and Yakutsk digisondes and found that the LSTIDs are most likely to come from the northern auroral region. These LSTIDs may be induced by the atmospheric gravity waves (AGWs) and presented obvious seasonal and diurnal varying features, indicating that the thermospheric wind field has played an important role.