An Ionosphere Specification Technique Based on Data Ingestion Algorithm and Empirical Orthogonal Function Analysis Method

A data ingestion method in reproducing ionospheric electron density and total electron content (TEC) was developed to incorporate TEC products from the Madrigal Database into the NeQuick 2 model. The method is based on retrieving an appropriate global distribution of effective ionization parameter (Az) to drive the NeQuick 2 model, which can be implemented through minimizing the difference between the measured and modeled TEC at each grid in the local time‐modified dip latitude coordinates. The performance of this Madrigal TEC‐driven‐NeQuick 2 result is validated through the comparison with various International Global Navigation Satellite Systems Services global ionospheric maps and ionosonde data. The validation results show that a general accuracy improvement of 30–50% can be achieved after data ingestion. In addition, the empirical orthogonal function (EOF) analysis technique is used to construct a parameterized time‐varying global Az model. The quick convergence of EOF decomposition makes it possible to use the first six EOF series to represent over 90% of the total variances. The intrinsic diurnal variation and spatial distribution in the original data set can be well reflected by the constructed EOF base functions. The associated EOF coefficients can be expressed as a set of linear functions of F10.7 and Ap indices, combined with a series of trigonometric functions with annual/seasonal variation components. The NeQuick TEC driven by EOF‐modeled Az shows 10–15% improvement in accuracy over the standard ionosphere correction algorithm in the Galileo navigation system. These preliminary results demonstrate the effectiveness of the combined data ingestion and EOF modeling technique in improving the specifications of ionospheric density variations.Key PointsThe Madrigal TEC data are ingested into the NeQuick 2 model through deriving an effective ionization parameter (Az)The Empirical Orthogonal Function (EOF) analysis technique is used to construct a parameterized time‐varying Az model to make a predictionThe TEC data ingestion and EOF modeling are effective in bringing certain systematic improvement of ionosphere now‐cast/forecastPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146373/1/swe20760_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146373/2/swe20760.pd

Midlatitude Plasma Bubbles Over China and Adjacent Areas During a Magnetic Storm on 8 September 2017

This paper presents observations of postsunset super plasma bubbles over China and adjacent areas during the second main phase of a storm on 8 September 2017. The signatures of the plasma bubbles can be seen or deduced from (1) deep field‐aligned total electron content depletions embedded in regional ionospheric maps derived from dense Global Navigation Satellite System networks, (2) significant equatorial and midlatitudinal plasma bite‐outs in electron density measurements on board Swarm satellites, and (3) enhancements of ionosonde virtual height and scintillation in local evening associated with strong southward interplanetary magnetic field. The bubbles/depletions covered a broad area mainly within 20°–45°N and 80°–110°E with bifurcated structures and persisted for nearly 5 hr (∼13–18 UT). One prominent feature is that the bubbles extended remarkably along the magnetic field lines in the form of depleted flux tubes, reaching up to midlatitude of around 50°N (magnetic latitude: 45.5°N) that maps to an altitude of 6,600 km over the magnetic equator. The maximum upward drift speed of the bubbles over the magnetic equator was about 700 m/s and gradually decreased with altitude and time. The possible triggering mechanism of the plasma bubbles was estimated to be storm time eastward prompt penetration electric field, while the traveling ionospheric disturbance could play a role in facilitating the latitudinal extension of the depletions.Key PointsPostsunset midlatitude plasma bubbles were observed over China and adjacent areas using GNSS TEC, Swarm Ne, and ionosonde dataThe plasma bubbles were triggered by PPEF and TID in equatorial regions and extended along the magnetic field lines to 50°N (45.5 MLAT)Plasma bubbles might reach an altitude of 6,600 km over the magnetic equator with the upper limit of upward drift speed being around 700 m/sPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143723/1/swe20573.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143723/2/swe20573_am.pd

Ionosonde Observations of Spread F and Spread Es at Low and Middle Latitudes during the Recovery Phase of the 7–9 September 2017 Geomagnetic Storm

This study presents observations of nighttime spread F/ionospheric irregularities and spread Es at low and middle latitudes in the South East Asia longitude of China sectors during the recovery phase of the 7–9 September 2017 geomagnetic storm. In this study, multiple observations, including a chain of three ionosondes located about the longitude of 100°E, Swarm satellites, and Global Navigation Satellite System (GNSS) ROTI maps, were used to study the development process and evolution characteristics of the nighttime spread F/ionospheric irregularities at low and middle latitudes. Interestingly, spread F and intense spread Es were simultaneously observed by three ionosondes during the recovery phase. Moreover, associated ionospheric irregularities could be observed by Swarm satellites and ground-based GNSS ionospheric TEC. Nighttime spread F and spread Es at low and middle latitudes might be due to multiple off-vertical reflection echoes from the large-scale tilts in the bottom ionosphere. In addition, we found that the periods of the disturbance ionosphere are ~1 h at ZHY station, ~1.5 h at LSH station and ~1 h at PUR station, respectively. It suggested that the large-scale tilts in the bottom ionosphere might be produced by LSTIDs (Large scale Traveling Ionospheric Disturbances), which might be induced by the high-latitude energy inputs during the recovery phase of this storm. Furthermore, the associated ionospheric irregularities observed by satellites and ground-based GNSS receivers might be caused by the local electric field induced by LSTIDs

Ionosonde Observations of Spread F and Spread Es at Low and Middle Latitudes during the Recovery Phase of the 7–9 September 2017 Geomagnetic Storm

This study presents observations of nighttime spread F/ionospheric irregularities and spread Es at low and middle latitudes in the South East Asia longitude of China sectors during the recovery phase of the 7–9 September 2017 geomagnetic storm. In this study, multiple observations, including a chain of three ionosondes located about the longitude of 100°E, Swarm satellites, and Global Navigation Satellite System (GNSS) ROTI maps, were used to study the development process and evolution characteristics of the nighttime spread F/ionospheric irregularities at low and middle latitudes. Interestingly, spread F and intense spread Es were simultaneously observed by three ionosondes during the recovery phase. Moreover, associated ionospheric irregularities could be observed by Swarm satellites and ground-based GNSS ionospheric TEC. Nighttime spread F and spread Es at low and middle latitudes might be due to multiple off-vertical reflection echoes from the large-scale tilts in the bottom ionosphere. In addition, we found that the periods of the disturbance ionosphere are ~1 h at ZHY station, ~1.5 h at LSH station and ~1 h at PUR station, respectively. It suggested that the large-scale tilts in the bottom ionosphere might be produced by LSTIDs (Large scale Traveling Ionospheric Disturbances), which might be induced by the high-latitude energy inputs during the recovery phase of this storm. Furthermore, the associated ionospheric irregularities observed by satellites and ground-based GNSS receivers might be caused by the local electric field induced by LSTIDs

Comparative Study of the Es Layer between the Plateau and Plain Regions in China

The lower atmosphere forcing plays an important role in forming the sporadic E (Es) layer in the ionosphere. In this study, a comparative study of the Es layer recorded by ionosondes at the middle latitude regions was carried out between the plateau and plain regions in China. The two ionosonde stations (Zhangye, 39.21°N, 100.54°E and Beijing, 40.25°N, 116.25°E) are located at the Qinghai–Tibet Plateau and North China Plain, respectively. The data during the year 2018 were used to reveal the characteristics of the Es layer. The occurrence probability, the critical frequency (foEs) and the base virtual height (h’Es) were considered in this study. Results show that: (1) The diurnal and seasonal variations of the occurrence probability between these two regions are similar. The maximum occurrence probability is at noontime and in the summer season. However, the Es at Zhangye occurred more frequently than Beijing at nighttime and in winter to early spring. (2) Similar to previous studies, the maximum value of foEs at Beijing mainly occurred in summer. Interestingly, the maximum value is in winter at Zhangye station. (3) The characteristics of the anomaly of the Es layer at Zhangye are mostly consistent with the characteristics of atmospheric gravity waves in the Qinghai–Tibet Plateau. Therefore, compared with observations at Beijing, the anomalies of the Es layer at Zhangye (at night and in winter to spring) might be attributed to gravity waves in the lower atmosphere over the Qinghai–Tibet Plateau

Synthesis of Gallic Acid-Derived Plasticizers for Polyvinyl Chloride Featuring Excellent Plasticization, Thermo-Stability, and Migration Resistance

The development of a facile and environmental strategy for manufacturing a natural aromatic-derived plasticizer for poly(vinyl chloride) (PVC) featuring excellent plasticization, UV-shielding, and thermostability, together with migration resistance, is still a challenge. Herein, a series of gallic acid-derived polypropylene glycol monomethyl ether esters with natural aromatic rings (TGPME-n, n = 1, 2, or 3 referring to the number of methylethoxy units in the structure of TGPME-n) were developed as plasticizers for PVC via the simple esterification of gallic acid with polypropylene glycol monomethyl ether and sequent etherification with epichlorohydrin in a one-pot process without any HCl generation. Extensive experiments showed that the performances of PVC blended with TGPME-n were highly dependent on the number of methylethoxy units from TGPME-n, where the performances of PVC plasticized by TGPME-n with more methylethoxy units were better than those of TGPME-n bearing one. Benefiting from the strong interaction of aromatic and polar groups (epoxy, ethoxy, and ester groups) in TGPME-n with a PVC skeleton, plasticization, low temperature resistance, thermal stability, transparency, and UV-shielding as well as migration resistance of PVC plasticized by TGPME-3 with maximum methylethoxy units were superior to those of PVC blended with dioctyl phthalate (DOP), implying that TGPME-3 could be used as an attractive alternative to totally replace the toxic DOP. This study provides a simple and feasible strategy to fabricate a highly efficient natural aromatic-derived plasticizer for the PVC industry

Comparative Study of the Es Layer between the Plateau and Plain Regions in China

The lower atmosphere forcing plays an important role in forming the sporadic E (Es) layer in the ionosphere. In this study, a comparative study of the Es layer recorded by ionosondes at the middle latitude regions was carried out between the plateau and plain regions in China. The two ionosonde stations (Zhangye, 39.21°N, 100.54°E and Beijing, 40.25°N, 116.25°E) are located at the Qinghai–Tibet Plateau and North China Plain, respectively. The data during the year 2018 were used to reveal the characteristics of the Es layer. The occurrence probability, the critical frequency (foEs) and the base virtual height (h’Es) were considered in this study. Results show that: (1) The diurnal and seasonal variations of the occurrence probability between these two regions are similar. The maximum occurrence probability is at noontime and in the summer season. However, the Es at Zhangye occurred more frequently than Beijing at nighttime and in winter to early spring. (2) Similar to previous studies, the maximum value of foEs at Beijing mainly occurred in summer. Interestingly, the maximum value is in winter at Zhangye station. (3) The characteristics of the anomaly of the Es layer at Zhangye are mostly consistent with the characteristics of atmospheric gravity waves in the Qinghai–Tibet Plateau. Therefore, compared with observations at Beijing, the anomalies of the Es layer at Zhangye (at night and in winter to spring) might be attributed to gravity waves in the lower atmosphere over the Qinghai–Tibet Plateau

Midlatitude Plasma Bubbles Over China and Adjacent Areas During a Magnetic Storm on 8 September 2017

This paper presents observations of postsunset super plasma bubbles over China and adjacent areas during the second main phase of a storm on 8 September 2017. The signatures of the plasma bubbles can be seen or deduced from (1) deep field‐aligned total electron content depletions embedded in regional ionospheric maps derived from dense Global Navigation Satellite System networks, (2) significant equatorial and midlatitudinal plasma bite‐outs in electron density measurements on board Swarm satellites, and (3) enhancements of ionosonde virtual height and scintillation in local evening associated with strong southward interplanetary magnetic field. The bubbles/depletions covered a broad area mainly within 20°–45°N and 80°–110°E with bifurcated structures and persisted for nearly 5 hr (∼13–18 UT). One prominent feature is that the bubbles extended remarkably along the magnetic field lines in the form of depleted flux tubes, reaching up to midlatitude of around 50°N (magnetic latitude: 45.5°N) that maps to an altitude of 6,600 km over the magnetic equator. The maximum upward drift speed of the bubbles over the magnetic equator was about 700 m/s and gradually decreased with altitude and time. The possible triggering mechanism of the plasma bubbles was estimated to be storm time eastward prompt penetration electric field, while the traveling ionospheric disturbance could play a role in facilitating the latitudinal extension of the depletions.Key PointsPostsunset midlatitude plasma bubbles were observed over China and adjacent areas using GNSS TEC, Swarm Ne, and ionosonde dataThe plasma bubbles were triggered by PPEF and TID in equatorial regions and extended along the magnetic field lines to 50°N (45.5 MLAT)Plasma bubbles might reach an altitude of 6,600 km over the magnetic equator with the upper limit of upward drift speed being around 700 m/sPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143723/1/swe20573.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143723/2/swe20573_am.pd