地磁暴发生时,电离层会有偏离平均水平的强烈扰动.基于全球电离层TEC及其时间变化率ROTI(Rate of TEC Index)数据,对2014年8月一次中等强度磁暴期间的全球电离层影响进行了分析,探讨了磁暴所引发电离层暴的可能机制.研究发现,本次磁暴...地磁暴发生时,电离层会有偏离平均水平的强烈扰动.基于全球电离层TEC及其时间变化率ROTI(Rate of TEC Index)数据,对2014年8月一次中等强度磁暴期间的全球电离层影响进行了分析,探讨了磁暴所引发电离层暴的可能机制.研究发现,本次磁暴伴随有明显的电离层暴效应.磁暴期间:南半球电离层以正相暴为主,北半球电离层暴则整体表现为短暂正相暴后长时间强的负相暴;电离层在北半球的下降比南半球强,并且这种下降持续了约一周时间;低纬区域电离层变化幅度明显小于中纬区域,高纬区域则主要表现为负暴效应;赤道北驼峰出现了明显的南移现象,直至磁赤道两侧双驼峰结构消失.对磁暴期间三个不同扇区的电离层ROTI变化的分析表明:欧洲—非洲扇区磁暴前有电离层闪烁发生,磁暴发生后消失,而东亚—澳大利亚及美洲扇区则无此现象出现.研究结果表明,此次磁暴期间的电离层变化存在明显的时间和空间差异.展开更多
The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from ...The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.展开更多
The rate of the total electron content(TEC)change index(ROTI)can be regarded as an effective indicator of the level of ionospheric scintillation,in particular in low and high latitude regions.An accurate prediction of...The rate of the total electron content(TEC)change index(ROTI)can be regarded as an effective indicator of the level of ionospheric scintillation,in particular in low and high latitude regions.An accurate prediction of the ROTI is essential to reduce the impact of the ionospheric scintillation on earth observation systems,such as the global navigation satellite systems.However,it is difficult to predict the ROTI with high accuracy because of the complexity of the ionosphere.In this study,advanced machine learning methods have been investigated for ROTI prediction over a station at high-latitude in Canada.These methods are used to predict the ROTI in the next 5 minutes using the data derived from the past 15 minutes at the same location.Experimental results show that the method of the bidirectional gated recurrent unit network(BGRU)outperforms the other six approaches tested in the research.It is also confirmed that the RMSEs of the predicted ROTI using the BGRU method in all four seasons of 2017 are less than 0.05 TECU/min.It is demonstrated that the BGRU method exhibits a high level of robustness in dealing with abrupt solar activities.展开更多
基于IGS提供的TEC数据,研究了2003年10月大磁暴期间的暴时密度增强(Storm EnhancedDensity,SED)现象;利用GPS观测数据,计算出ROTI(Standard deviations of ROT)指数,分析了SED边界附近电离层小尺度不均匀体结构的时间和空间演变.研究表...基于IGS提供的TEC数据,研究了2003年10月大磁暴期间的暴时密度增强(Storm EnhancedDensity,SED)现象;利用GPS观测数据,计算出ROTI(Standard deviations of ROT)指数,分析了SED边界附近电离层小尺度不均匀体结构的时间和空间演变.研究表明,在磁暴主相期间SED边界附近不均匀体随着磁暴的发展逐渐增多;在主相的中后期不均匀体的分布密集度达到最大;在恢复相期间,不均匀体分布很少;随着磁暴的发展,不均匀体开始主要集中在40°～45°N范围内,随后向高纬漂移,主要集中在45°～55°N范围内.展开更多
Flat breads are very popular especially in those parts of the world where bread constitutes a major source of dietary protein and calories. There are several forms of flat bread, and the variation is mainly in terms o...Flat breads are very popular especially in those parts of the world where bread constitutes a major source of dietary protein and calories. There are several forms of flat bread, and the variation is mainly in terms of ingredient, technology, and quality. Several modifications in the formulations have been made in the recent past in order to improve the quality and delicacy of these food products. With urbanization and industrialization, the demand for ready to eat and easy to carry products resembling flat bread in appearance, but having desirable qualities of bread offers one exciting possibility to this effect. In India, wheat is one of the daily staples, consumed in the form of different flat breads such as Chapati, Parotha, Phulka, Puri and Tandoori Roti. Different wheat varieties have been used for the production of flat breads. In recent years, many researchers have tried to improve ingredient level, baking properties, organoleptic characteristics, nutritional value and extension of the shelf life of flat bread. They are usually produced from a simple recipe consisting of flour, salt and water in varying proportions, however, sometimes the manufactures also use optional ingredients like yeast fat, skim milk powder and certain additives like emulsifiers, hydrocolloids, enzymes and preservatives for quality improvement and shelf life enhancement.展开更多
In this study,the global effects of the severe geomagnetic storm on the Earth’s ionosphere on September5 e9,2017 with Coronal Mass Ejections(CMEs)associated with X-9.3 flares on September 6,2017 were investigated by ...In this study,the global effects of the severe geomagnetic storm on the Earth’s ionosphere on September5 e9,2017 with Coronal Mass Ejections(CMEs)associated with X-9.3 flares on September 6,2017 were investigated by the Rate of Total Electron Content(TEC)Index(ROTI).ROTI was used as a criterion of ionospheric irregularities that took place during the storm.This study was conducted with TEC values obtained from fifty stations connected to the International GNSS System(IGS)-GPS network for five different latitude regions.As a result,it was observed that the irregularities in the high latitude regions of the southern hemisphere were greater in number in comparison with those at the high latitude regions of the northern hemisphere during the storm.It was observed that these irregularities generally occurred during the main and recovery phases of the storm at all latitudes.The weak and moderate ionospheric irregularities that developed at high latitudes during the storm were more in the southern hemisphere.Especially,moderate ionospheric irregularities in high latitudes of both hemispheres took place in eastern longitudes(18 oE-160 oE).However,ionospheric irregularities in the mid-latitude regions were observed in more stations at the northern hemisphere than at the southern hemisphere.Generally,ionospheric irregularities during the storm developed at eastern longitudes in all sectors.展开更多
文摘地磁暴发生时,电离层会有偏离平均水平的强烈扰动.基于全球电离层TEC及其时间变化率ROTI(Rate of TEC Index)数据,对2014年8月一次中等强度磁暴期间的全球电离层影响进行了分析,探讨了磁暴所引发电离层暴的可能机制.研究发现,本次磁暴伴随有明显的电离层暴效应.磁暴期间:南半球电离层以正相暴为主,北半球电离层暴则整体表现为短暂正相暴后长时间强的负相暴;电离层在北半球的下降比南半球强,并且这种下降持续了约一周时间;低纬区域电离层变化幅度明显小于中纬区域,高纬区域则主要表现为负暴效应;赤道北驼峰出现了明显的南移现象,直至磁赤道两侧双驼峰结构消失.对磁暴期间三个不同扇区的电离层ROTI变化的分析表明:欧洲—非洲扇区磁暴前有电离层闪烁发生,磁暴发生后消失,而东亚—澳大利亚及美洲扇区则无此现象出现.研究结果表明,此次磁暴期间的电离层变化存在明显的时间和空间差异.
基金Supported by the National Natural Science Young Foundation of China(41704168)。
文摘The observations of Global Positioning System(GPS) scintillation,Total Electron Content(TEC)depletion,the periodic structure of TEC and Rate of TEC Index(ROTI) over south China were presented.Data were collected from GPS observations at stations of Shenzhen and Guangzhou from 2011 to 2012.This study reported that the ratio of simultaneous occurrences of TEC depletions with strong scintillations was higher than that of TEC depletions with weak scintillations in vernal and autumnal equinoxes of 2011 over South China.The number of the periodic structures of TEC with depletion contained was greater than that with no depletion contained corresponding to strong scintillations.The structure of the slab of plasma irregularities could be responsible for the simultaneous occurrences of TEC depletion with strong scintillations and ROTI.Before and during the occurrences of strong scintillation,there was Large-Scale Wave Structure(LSWS) which provided the seed ionization perturbation to trigger ESF irregularities and contributed to the periodic structure of TEC.
基金National Key Research Program of China(No.2017YFE0131400)National Natural Science Foundation of China(Nos.41674043,41704038,41874040)+2 种基金Beijing Nova Program(No.xx2017042)Beijing Talents Foundation(No.2017000021223ZK13)CUMT Independent Innovation Project of“Double-First Class”Construction(No.2018ZZ08)。
文摘The rate of the total electron content(TEC)change index(ROTI)can be regarded as an effective indicator of the level of ionospheric scintillation,in particular in low and high latitude regions.An accurate prediction of the ROTI is essential to reduce the impact of the ionospheric scintillation on earth observation systems,such as the global navigation satellite systems.However,it is difficult to predict the ROTI with high accuracy because of the complexity of the ionosphere.In this study,advanced machine learning methods have been investigated for ROTI prediction over a station at high-latitude in Canada.These methods are used to predict the ROTI in the next 5 minutes using the data derived from the past 15 minutes at the same location.Experimental results show that the method of the bidirectional gated recurrent unit network(BGRU)outperforms the other six approaches tested in the research.It is also confirmed that the RMSEs of the predicted ROTI using the BGRU method in all four seasons of 2017 are less than 0.05 TECU/min.It is demonstrated that the BGRU method exhibits a high level of robustness in dealing with abrupt solar activities.
文摘基于IGS提供的TEC数据,研究了2003年10月大磁暴期间的暴时密度增强(Storm EnhancedDensity,SED)现象;利用GPS观测数据,计算出ROTI(Standard deviations of ROT)指数,分析了SED边界附近电离层小尺度不均匀体结构的时间和空间演变.研究表明,在磁暴主相期间SED边界附近不均匀体随着磁暴的发展逐渐增多;在主相的中后期不均匀体的分布密集度达到最大;在恢复相期间,不均匀体分布很少;随着磁暴的发展,不均匀体开始主要集中在40°～45°N范围内,随后向高纬漂移,主要集中在45°～55°N范围内.
文摘Flat breads are very popular especially in those parts of the world where bread constitutes a major source of dietary protein and calories. There are several forms of flat bread, and the variation is mainly in terms of ingredient, technology, and quality. Several modifications in the formulations have been made in the recent past in order to improve the quality and delicacy of these food products. With urbanization and industrialization, the demand for ready to eat and easy to carry products resembling flat bread in appearance, but having desirable qualities of bread offers one exciting possibility to this effect. In India, wheat is one of the daily staples, consumed in the form of different flat breads such as Chapati, Parotha, Phulka, Puri and Tandoori Roti. Different wheat varieties have been used for the production of flat breads. In recent years, many researchers have tried to improve ingredient level, baking properties, organoleptic characteristics, nutritional value and extension of the shelf life of flat bread. They are usually produced from a simple recipe consisting of flour, salt and water in varying proportions, however, sometimes the manufactures also use optional ingredients like yeast fat, skim milk powder and certain additives like emulsifiers, hydrocolloids, enzymes and preservatives for quality improvement and shelf life enhancement.
文摘In this study,the global effects of the severe geomagnetic storm on the Earth’s ionosphere on September5 e9,2017 with Coronal Mass Ejections(CMEs)associated with X-9.3 flares on September 6,2017 were investigated by the Rate of Total Electron Content(TEC)Index(ROTI).ROTI was used as a criterion of ionospheric irregularities that took place during the storm.This study was conducted with TEC values obtained from fifty stations connected to the International GNSS System(IGS)-GPS network for five different latitude regions.As a result,it was observed that the irregularities in the high latitude regions of the southern hemisphere were greater in number in comparison with those at the high latitude regions of the northern hemisphere during the storm.It was observed that these irregularities generally occurred during the main and recovery phases of the storm at all latitudes.The weak and moderate ionospheric irregularities that developed at high latitudes during the storm were more in the southern hemisphere.Especially,moderate ionospheric irregularities in high latitudes of both hemispheres took place in eastern longitudes(18 oE-160 oE).However,ionospheric irregularities in the mid-latitude regions were observed in more stations at the northern hemisphere than at the southern hemisphere.Generally,ionospheric irregularities during the storm developed at eastern longitudes in all sectors.
