Analysis of Anomalous Enhancement in TEC and Electron Density in the China Region Prior to the 17 March 2015 Geomagnetic Storm Based on Ground and Space Observations

Total Electron Content(TEC)and electron density enhancement were observed on the day before 17 March 2015 great storm in the China Region.Observations from ground-and space-based instruments are used to investigate the temporal and spatial evolution of the pre-storm enhancement.TEC enhancement was observed from 24°N to 30°N after 10:00 UT at 105°E,110°E and 115°E longitudes on March 16.The maximum magnitude of TEC enhancement was more than 10 TECU and the maximal relative TEC enhancement exceeded 30%.Compared with geomagnetic quiet days,the electron density of Equatorial Ionization Anomaly(EIA)northern peak from Swarm A/C satellites on March 16 was larger and at higher latitudes.NmF2 enhanced during 11:30—21:00 UT at Shaoyang Station and increased by 200%at~16:00 UT.However,TEC and electron density enhancement were not accompanied by a significant change of hmF2.Most research has excluded some potential mechanisms as the main driving factors for storm-time density enhancements by establishing observational constraints.In this paper,we observed pre-storm enhancement in electron density at different altitudes and Equatorial Electrojet(EEJ)strength results derived from ground magnetometers observations suggest an enhanced eastward electric field from the E region probably played a significant role in this event.

Suppression of Plasma Bubbles over South America under Weak Geomagnetic Perturbations

During a long-term Equatorial Plasma Bubbles(EPBs)occurrence between October 2020 and March 2021,a significant EPB suppression event was identified on November 22 and the observations from multi-instrument have been utilized to investigate this event.Global-scale Observations of the Limb and Disk(GOLD)satellite observed prominent EPBs between 23:40 UT and 23:55 UT during the long-term occurrence days.However,no dark stripes representing EPBs were observed on November 22,and the Equatorial Ionization Anomaly(EIA)structure remained intact.The Total Electron Content(TEC)maps show that these EPBs appeared in the region between 35°W and 65°W longitudes and the magnitudes of the TEC loss in EPBs regions were about 20 TECU.Except for 22 November,the S4 index was consistently greater than 0.6 throughout November,indicating significant ionospheric scintillation.The Rate Of TEC Index(ROTI)maps revealed that the spatial extent and intensity of EPBs increased after their suppression,and the EPBs were locally generated.The swarm electron density measurements indicated that the variation amplitudes of EPBs at 510 km altitude were approximately 3 to 5 times larger than that at 460 km altitude.The impact region of EPBs at 510 km was between 15°S and 20°N latitudes,while at 460 km,it was between 0°and 17°N latitudes.During the period of EPB suppression,the average h’f at three ionosonde stations decreased by about 50 km,and the vertical drift velocity(V z)approached~0 m/s while it was more than 20 m/s during the long-term occurrence.

Research and applications of artificial neural network in pavement engineering:A state-of-the-art review

Given the great advancements in soft computing and data science,artificial neural network(ANN)has been explored and applied to handle complicated problems in the field of pavement engineering.This study conducted a state-of-the-art review for surveying the recent progress of ANN application at different stages of pavement engineering,including pavement design,construction,inspection and monitoring,and maintenance.This study focused on the papers published over the last three decades,especially the studies conducted since 2013.Through literature retrieval,a total of 683 papers in this field were identified,among which 143 papers were selected for an in-depth review.The ANN architectures used in these studies mainly included multi-layer perceptron neural network(MLPNN),convolutional neural network(CNN)and recurrent neural network(RNN)for processing one-dimensional data,two-dimensional data and time-series data.CNN-based pavement health inspection and monitoring attracted the largest research interest due to its potential to replace human labor.While ANN has been proved to be an effective tool for pavement material design,cost analysis,defect detection and maintenance planning,it is facing huge challenges in terms of data collection,parameter optimization,model transferability and low-cost data annotation.More attention should be paid to bring multidisciplinary techniques into pavement engineering to tackle existing challenges and widen future opportunities.