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A statistical analysis of sporadic E layer recorded from September 2011 to September 2015 at four Chinese ionospheric sounding stations of Mohe (122.37°E, 53.50°N), Beijing (116.25°E, 40.25°N), Wuhan (114.61°E, 30.53°N), and Hainan (109.13°E, 19.52°N) is presented to investigate the characteristics of sporadic E layer at the middle latitudes over China. The occurrence of the sporadic E layer in midlatitude China region shows strong dependence on local time and season, consistent with previous studies. The occurrence of the midlatitude sporadic E layer is prominent at local daytime in summer season. The results also reveal that the postsunset sporadic E layer is statistically pronounced in midlatitude China region, possibly related to the nighttime midlatitude E region irregularities. The midlatitude sporadic E layer is modulated by atmospheric tidal waves and planetary waves at different latitudes. The occurrence of the midlatitude sporadic E layer also tends to increase with the level of geomagnetic activity on the basis of both the statistical analysis and case study.

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Coupling of ionospheric E and F regions in the midlatitude region has been studied for a couple of years. In this study, we investigate the nighttime disturbances in E and F regions in midlatitude China region by using Wuhan ionosonde, Wuhan very high frequency coherent scatter radar, and Mengcheng airglow imager. We present two case studies of simultaneous observations of diffuse sporadic E (Es) layers, quasiperiodic echoes of E region irregularities, spread F, and medium-scale traveling ionospheric disturbances. Results of case studies indicate that diffuse Es layers and E region irregularities can be associated with the F region medium-scale traveling ionospheric disturbances or spread F through polarization electric field mapping along the field lines. We then analyze the data set of Wuhan ionosonde and Wuhan very high frequency radar during 2015-2016 and find that the coincidence of diffuse Es layers, quasiperiodic echoes of E region irregularities, and spread F is high at local nighttime. Our results provide the first observational evidence in midlatitude China region to support the concept that polarization electric field generated in the E region irregularities could map along the magnetic field lines and excite electrodynamic disturbances in F region, such as Perkins instability.

We report a statistical study of medium-scale traveling ionospheric disturbances (MSTIDs) during 2014-2017 in the low-latitude China region using the Hong Kong Continuously Operating Reference Stations network with a baseline length of 10-15 km. Polynomial fitting and the multichannel maximum entropy method are utilized to derive MSTID parameters from global positioning system total electron content data. We find that MSTIDs can be sorted into three types in this region. One type is daytime MSTIDs, which are mainly distributed during 1000-1700 local time (LT) in spring, autumn and winter. The second type is nighttime MSTIDs, which mainly occur from 2200 to 0300 LT in spring and summer. The third type is morning MSTIDs, mainly occurring from 0500 to 0700 LT in spring and autumn. No clear difference in the MSTID parameters is distinguishable between the cyclone period and non-cyclone period, which may be due to the distance restriction for cyclone identification and different propagation distances of the primary gravity waves (GWs) and secondary GWs.

We are in the evolution of continuous monitoring of neural activity with non-invasive wearable EEGs. The development of hydrogel electrodes technology is important for home-use systems for long-term EEG monitoring and diagnostics of disease.

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This study presents the statistical features of ionospheric E-F coupling and interhemispheric coupling at midlatitudes. Nighttime ionospheric E and F region irregularity occurrences are investigated by using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation measurements during 2006-2018. We presented four typical events of simultaneous observations of E and F region irregularities in the local hemisphere and F region irregularities in both conjugate hemispheres. Results of case studies indicate the coincidence of ionospheric irregularities in both E and F regions, as well as the coincidence of ionospheric irregularities in both F regions of two conjugate hemispheres. Statistical analysis of occurrences of E and F region irregularities shows that the concurrence of ionospheric irregularities in both E and F regions reaches a maximum (nearly 70%) during June (December) solstice in the Northern (Southern) Hemisphere. Nearly 50% (45%) of the F region irregularity in the Northern (Southern) Hemisphere occurs simultaneously with F region irregularity occurrence in the Southern (Northern) Hemisphere during December (June) solstice. These results provide the observational evidences showing that the effect of E-F coupling and interhemispheric coupling may be important in generation of midlatitude nighttime F region irregularity. In addition, our results also reveal that mapping efficiency of electrodynamic coupling has a different seasonal variation in the Northern and Southern Hemispheres, which shows dependence on both the integrated Pedersen conductivity of F region (∑ F P