Despite the continuous improvement of the widely used empirical model international reference ionosphere(IRI),the recently appeared new models must be tested worldwide.Testing along the meridians has the advantage of ...Despite the continuous improvement of the widely used empirical model international reference ionosphere(IRI),the recently appeared new models must be tested worldwide.Testing along the meridians has the advantage of dealing with the latitudinal dependent parameters.This paper uses new models of parameters foF2(critical frequency),TEC(total electron content),andτ(equivalent slab thickness of the ionosphere),which are of great importance for evaluating the effects of space weather.IRI-Plas,NNT2F2,and NTSM models were tested using data from 6 ionosondes located along the meridian 110°E in March 2012.It is shown that the IRI-Plas model provides the closest values to experiment with respect toτ,while the NTSM model provides a rather limited reflection of the latitude dependence.Analyses of foF2(NNT2F2)have shown that,the NNT2F2 model provides good conformity with experimental values in this area,but it is very dependent on the TEC processing method.The latitudinal dependences of foF2 obtained with TEC and polynomial dependenceτ(Appr)showed the presence of positive deviations from medians not only during disturbances but also quiet periods,longitudinally at the meridian.展开更多
To understand the physics of an ionospheric E-F valley, a new overlapping three- Chapman-layer model is developed to interpret the sounding rocket measurement in the morn- ing （sunrise） on May 7, 2011 at the Hainan ...To understand the physics of an ionospheric E-F valley, a new overlapping three- Chapman-layer model is developed to interpret the sounding rocket measurement in the morn- ing （sunrise） on May 7, 2011 at the Hainan low latitude ionospheric observation station （19.5°N, 109.1°E）. From our model, the valley width, depth and height are 43.0 km, 62.9% and 121.0 km, re- spectively. From the sounding rocket observation, the valley width, depth and height are 42.2 km, 47.0% and 123.5 km, respectively. The model results are well consistent with the sounding rocket observation. The observed E-F valley at Hainan station is very wide and deep, and rapid deel- opment of the photochemical process in the ionosphere should be the underlying reason.展开更多
This study deals with Peak of electron density in F2-layer sensibility scale during quiet time on solar minimum. Peaks of electron density in F2-layer (NmF2) values at the quietest days are compared to those carried o...This study deals with Peak of electron density in F2-layer sensibility scale during quiet time on solar minimum. Peaks of electron density in F2-layer (NmF2) values at the quietest days are compared to those carried out from the two nearest days (previous and following of quietest day). The study uses International Reference Ionosphere (IRI) for ionosphere modeling. The located station is Ouagadougou, in West Africa. Solar minimum of phase 22 is considered in this study. Using three core principles of ionosphere modeling under IRI running conditions, the study enables to carry out Peak of electron density in F2-layer values during the quietest days of the characteristic months for the four different seasons. These parameters are compared to those of the previous and the following of the quietest days (the day before and following each quietest selected day) at the same hour. The knowledge of NmF2 values at the quietest days and at the two nearest days enables to calculate the relative error that can be made on this parameter. This calculation highlights insignificant relative errors. This means that NmF2 values at the two nearest days of each quietest day on solar minimum can be used for simulating the quietest days’ behavior. NmF2 values obtained by running IRI model have good correlation with those carried out by Thermosphere-Ionosphere-Electrodynamics-General Circulation Model (TIEGCM).展开更多
In this study, the relationship between the QBO （quasi-biennial oscillation）, which is seen at the equatorial stratosphere, and critical frequency of layer （Es） sporadically observed at the ionospheric E region wa...In this study, the relationship between the QBO （quasi-biennial oscillation）, which is seen at the equatorial stratosphere, and critical frequency of layer （Es） sporadically observed at the ionospheric E region was analyzed by using multiple regression model. For this analysis, Es layer critical frequency （foEs） obtained from four different stations at equatorial region and QBO measured at 10 hPa altitude values were used. The positive relationship between foEs and QBO was observed at all stations. An increase of 1 m/s at QBO leads to an increase of 0.01 Mhz, 0.02 Mhz, 0.02 Mhz and 0.01 Mhz （Jicamarca, Ascension, Manila and Kwajalein） on foEs, respectively. Expect for Manila station, westerly phase of QBO has greater effect on foEs compared to easterly phase of QBO at all other stations. It is seen that the changes occurred on foEs can be explained by the QBO at rates 47%, 46%, 32% and 44% for Jicamarca, Ascension, Manila and Kwajalein stations, respectively.展开更多
Ionosphere layer is the atmosphere region which reflects radio waves for telecommunication. The density in particles in this layer influences the quality of communication. This study deals with the effects of Total El...Ionosphere layer is the atmosphere region which reflects radio waves for telecommunication. The density in particles in this layer influences the quality of communication. This study deals with the effects of Total Electron Contents (TEC) on the critical frequency of radio waves in the F2-layer. Total Electron Contents parameter symbolizes electron bulk surface density in ionosphere layer. Above critical frequency value in F2 layer (foF2), radio waves pass through ionosphere. The knowledge of this value enables to calibrate transmission frequencies. In this study, we consider TEC effects on foF2 under quiet time conditions during the maximum and the minimum of solar cycle 22, at Ouagadougou station, in West Africa. The study also considers the effects of seasons and the hourly variability of TEC and foF2. This work shows winter anomaly on foF2 and TEC on minimum and maximum of solar cycle phase respectively. Running International Reference Ionosphere (IRI) model enables to carry out the effects of TEC on foF2 by use of their monthly average values. This leads to a new approach to calibrate radio transmitters.展开更多
In the present work, disturbances of the half-transparency frequency fbEs of the ionospheric sporadic E-layer are investigated in connection with earthquakes. The fbEs-frequency is proportional to the square root of t...In the present work, disturbances of the half-transparency frequency fbEs of the ionospheric sporadic E-layer are investigated in connection with earthquakes. The fbEs-frequency is proportional to the square root of the maximum ionisation density of the sporadic E-layer. In this work, it is shown that in 2/3 of the cases, two days before a seismic shock with magnitude M > 5.5 and on the day of the shock, an increase of the fbEs-frequency is obtained at sunset hours at distances from the epicenter R km. In contrast, before sunrise, the fbEs-value decreases. The data analysed are obtained by the three vertical ionospheric sounding stations“Kokubunji”, “Yamagawa”, and “Wakkanai” during some tens of years.展开更多
On the basis of previous work, we develop a middle and low latitude theoretical ionospheric model in this paper, named Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Aca...On the basis of previous work, we develop a middle and low latitude theoretical ionospheric model in this paper, named Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME-IGGCAS). TIME-IGGCAS solves the equations of mass continuity, motion and energy of electron and ions self-consistently and uses an eccentric dipole field approxima-tion to the Earth’s magnetic field. We combine the Eulerian and Lagrangian approaches in the model and take account of the plasma E×B drift velocity. Calculation results reveal that the model is steady and credible and can reproduce most large-scale features of ionosphere. By using TIME-IGGCAS, we carried out an observation system data assimilation experiment. Assimilation results show that the E×B drift velocity can be accurately estimated by ingesting the observed foF2 and hmF2 into the model ap-plying nonlinear least-square fit method. We suggest that this work is of great significance in the de-velopment of ionospheric data assimilation model to give better nowcast and forecast of ionosphere.展开更多
A model for the negative phase of ionospheric storms in middle latitudes is presented. It is assumed that there will be molecule enriched air in the thermosphere above the auroral oval during the period of the main ph...A model for the negative phase of ionospheric storms in middle latitudes is presented. It is assumed that there will be molecule enriched air in the thermosphere above the auroral oval during the period of the main phase of a magnetic storm. The molecule enriched air is carried to the middle latitudes by thermospheric neutral wind, and at the same time it diffuses away. When the molecule enriched air arrives at the F2 layer above a station, the electron loss rate in the F2 layer increases, the electron density decreases and then the negative phase at the station begins. We have calculated the variations of the fo F2 following magnetic storms for Manzhouli （29.5°N, 117.5°E）, Freiburg （48°N, 07°E） and Billerica （43°N, 71°W） respectively. The results agree very well with typical events observed at the three stations and can be used to explain some average features of negative phase ionospheric storms in middle latitudes.展开更多
A theoretical model for ionospheric electric fields at mid- and low-latitudes is developed. In the geomagnetic dipolar coordinate system, we deduce a partial differential equation of electric potential from the ionosp...A theoretical model for ionospheric electric fields at mid- and low-latitudes is developed. In the geomagnetic dipolar coordinate system, we deduce a partial differential equation of electric potential from the ionospheric dynamo theory. The deduced equation is taken as the fundamental equation for the present model. The principal parameters for the model input, the thermospheric neutral winds, the densities and temperatures of electrons, ions and neutral atoms and molecules, are obtained from the empirical models HWM93, IRI90 and MSISE90, respectively. In terms of the relaxation iteration method, the partial equations for electric potential are solved successfully, and then, the ionospheric electric potential, fields, and currents are derived. Our model can reproduce the main features of the ionospheric electrodynamical processes such as the equatorial electric jet (EEJ), so it will be a useful tool for studying the upper atmosphere and ionosphere.展开更多
E层占优电离层是指E层的峰值电子密度大于F层的峰值电子密度(NmE>NmF)时的电离层,记为ELDI(E-Layer Dominated Ionosphere)。针对ELDI,利用2007—2010年的COSMIC(Constellation Observing System for Meteorolo-gy,Ionosphere,and Cl...E层占优电离层是指E层的峰值电子密度大于F层的峰值电子密度(NmE>NmF)时的电离层,记为ELDI(E-Layer Dominated Ionosphere)。针对ELDI,利用2007—2010年的COSMIC(Constellation Observing System for Meteorolo-gy,Ionosphere,and Climate satellite)掩星数据,在修正地磁纬度-磁地方时标系下统计分析了它在南北极区极夜期间(南北半球的冬至日前后30天)的分布特征,结果表明极夜期间电离层ELDI特征明显,其分布与极光椭圆位形基本一致,而且其在夜侧的发生率较高,特别是磁子夜之后,北极为70%左右,而南极为90%左右;另外南极的ELDI特征在磁纬度分布上要略宽于北极的分布范围。在ELDI高发区,电离层峰值电子密度要高于其两侧地区,特别是在夜侧,尤其是磁子夜前的峰值电子密度要接近甚至大于磁正午的峰值电子密度,在南极地区格外明显;而且ELDI高发区内的E层的电子含量(TECE)、电离层总电子含量(TECI)及TECE占TECI的比重(TECEI)都高于其两侧地区,北极TECE和TECI大于南极,而TECEI则是南极大于北极。这些现象主要是由于极夜期间极区高能粒子沉降引起底部电离层电离率增大所致;同时,由于地磁轴偏离地理轴的程度在南极要大于北极,使得极夜期间南极地区的电离层的电子密度,特别是在F层要相应地小于北极地区,从而导致了极夜期间南北半球极区电离层ELDI特征之间差异。展开更多
SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检...SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检验SAMI2在此扇区的电离层TEC计算精度.结果表明,物理模型输出的电离层TEC具备与观测数据一致的周日变化、季节变化,太阳活动变化.周日分布上,上午时段SAMI2 TEC与观测数据吻合度优于午后时段;季节分布上,SAMI2 TEC在冬季与观测值偏差小于其他季节;SAMI2 TEC与GPS TEC相关系数各站均达到0.87以上,与赤道地区Guam站相关性最好;太阳活动低年计算结果优于太阳活动高年;多数情况下,SAMI2 TEC相对GPS TEC偏大.本文结果为基于SAMI2模型构建背景误差分布特征,开展该区域电离层数值预报研究可行性提供了理论支持.展开更多
基金financially supported by Southern Federal University,Russia,2020 Project Vn Gr/2020-03-IF
文摘Despite the continuous improvement of the widely used empirical model international reference ionosphere(IRI),the recently appeared new models must be tested worldwide.Testing along the meridians has the advantage of dealing with the latitudinal dependent parameters.This paper uses new models of parameters foF2(critical frequency),TEC(total electron content),andτ(equivalent slab thickness of the ionosphere),which are of great importance for evaluating the effects of space weather.IRI-Plas,NNT2F2,and NTSM models were tested using data from 6 ionosondes located along the meridian 110°E in March 2012.It is shown that the IRI-Plas model provides the closest values to experiment with respect toτ,while the NTSM model provides a rather limited reflection of the latitude dependence.Analyses of foF2(NNT2F2)have shown that,the NNT2F2 model provides good conformity with experimental values in this area,but it is very dependent on the TEC processing method.The latitudinal dependences of foF2 obtained with TEC and polynomial dependenceτ(Appr)showed the presence of positive deviations from medians not only during disturbances but also quiet periods,longitudinally at the meridian.
基金supported by National Natural Science Foundation of China(No.41274146)the Specialized Research Fund for State Key Laboratory in China
文摘To understand the physics of an ionospheric E-F valley, a new overlapping three- Chapman-layer model is developed to interpret the sounding rocket measurement in the morn- ing （sunrise） on May 7, 2011 at the Hainan low latitude ionospheric observation station （19.5°N, 109.1°E）. From our model, the valley width, depth and height are 43.0 km, 62.9% and 121.0 km, re- spectively. From the sounding rocket observation, the valley width, depth and height are 42.2 km, 47.0% and 123.5 km, respectively. The model results are well consistent with the sounding rocket observation. The observed E-F valley at Hainan station is very wide and deep, and rapid deel- opment of the photochemical process in the ionosphere should be the underlying reason.
文摘This study deals with Peak of electron density in F2-layer sensibility scale during quiet time on solar minimum. Peaks of electron density in F2-layer (NmF2) values at the quietest days are compared to those carried out from the two nearest days (previous and following of quietest day). The study uses International Reference Ionosphere (IRI) for ionosphere modeling. The located station is Ouagadougou, in West Africa. Solar minimum of phase 22 is considered in this study. Using three core principles of ionosphere modeling under IRI running conditions, the study enables to carry out Peak of electron density in F2-layer values during the quietest days of the characteristic months for the four different seasons. These parameters are compared to those of the previous and the following of the quietest days (the day before and following each quietest selected day) at the same hour. The knowledge of NmF2 values at the quietest days and at the two nearest days enables to calculate the relative error that can be made on this parameter. This calculation highlights insignificant relative errors. This means that NmF2 values at the two nearest days of each quietest day on solar minimum can be used for simulating the quietest days’ behavior. NmF2 values obtained by running IRI model have good correlation with those carried out by Thermosphere-Ionosphere-Electrodynamics-General Circulation Model (TIEGCM).
文摘In this study, the relationship between the QBO （quasi-biennial oscillation）, which is seen at the equatorial stratosphere, and critical frequency of layer （Es） sporadically observed at the ionospheric E region was analyzed by using multiple regression model. For this analysis, Es layer critical frequency （foEs） obtained from four different stations at equatorial region and QBO measured at 10 hPa altitude values were used. The positive relationship between foEs and QBO was observed at all stations. An increase of 1 m/s at QBO leads to an increase of 0.01 Mhz, 0.02 Mhz, 0.02 Mhz and 0.01 Mhz （Jicamarca, Ascension, Manila and Kwajalein） on foEs, respectively. Expect for Manila station, westerly phase of QBO has greater effect on foEs compared to easterly phase of QBO at all other stations. It is seen that the changes occurred on foEs can be explained by the QBO at rates 47%, 46%, 32% and 44% for Jicamarca, Ascension, Manila and Kwajalein stations, respectively.
文摘Ionosphere layer is the atmosphere region which reflects radio waves for telecommunication. The density in particles in this layer influences the quality of communication. This study deals with the effects of Total Electron Contents (TEC) on the critical frequency of radio waves in the F2-layer. Total Electron Contents parameter symbolizes electron bulk surface density in ionosphere layer. Above critical frequency value in F2 layer (foF2), radio waves pass through ionosphere. The knowledge of this value enables to calibrate transmission frequencies. In this study, we consider TEC effects on foF2 under quiet time conditions during the maximum and the minimum of solar cycle 22, at Ouagadougou station, in West Africa. The study also considers the effects of seasons and the hourly variability of TEC and foF2. This work shows winter anomaly on foF2 and TEC on minimum and maximum of solar cycle phase respectively. Running International Reference Ionosphere (IRI) model enables to carry out the effects of TEC on foF2 by use of their monthly average values. This leads to a new approach to calibrate radio transmitters.
文摘In the present work, disturbances of the half-transparency frequency fbEs of the ionospheric sporadic E-layer are investigated in connection with earthquakes. The fbEs-frequency is proportional to the square root of the maximum ionisation density of the sporadic E-layer. In this work, it is shown that in 2/3 of the cases, two days before a seismic shock with magnitude M > 5.5 and on the day of the shock, an increase of the fbEs-frequency is obtained at sunset hours at distances from the epicenter R km. In contrast, before sunrise, the fbEs-value decreases. The data analysed are obtained by the three vertical ionospheric sounding stations“Kokubunji”, “Yamagawa”, and “Wakkanai” during some tens of years.
基金the Knowledge Innovation Project of Chinese Academy of Sciences (Grant No. KZCX3-SW-144)the National Natural Science Foundation of China (Grant Nos. 40636032, 40574071 and 40504023)National Important Basic Research Project (Grant No. 2006CB806306)
文摘On the basis of previous work, we develop a middle and low latitude theoretical ionospheric model in this paper, named Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME-IGGCAS). TIME-IGGCAS solves the equations of mass continuity, motion and energy of electron and ions self-consistently and uses an eccentric dipole field approxima-tion to the Earth’s magnetic field. We combine the Eulerian and Lagrangian approaches in the model and take account of the plasma E×B drift velocity. Calculation results reveal that the model is steady and credible and can reproduce most large-scale features of ionosphere. By using TIME-IGGCAS, we carried out an observation system data assimilation experiment. Assimilation results show that the E×B drift velocity can be accurately estimated by ingesting the observed foF2 and hmF2 into the model ap-plying nonlinear least-square fit method. We suggest that this work is of great significance in the de-velopment of ionospheric data assimilation model to give better nowcast and forecast of ionosphere.
文摘A model for the negative phase of ionospheric storms in middle latitudes is presented. It is assumed that there will be molecule enriched air in the thermosphere above the auroral oval during the period of the main phase of a magnetic storm. The molecule enriched air is carried to the middle latitudes by thermospheric neutral wind, and at the same time it diffuses away. When the molecule enriched air arrives at the F2 layer above a station, the electron loss rate in the F2 layer increases, the electron density decreases and then the negative phase at the station begins. We have calculated the variations of the fo F2 following magnetic storms for Manzhouli （29.5°N, 117.5°E）, Freiburg （48°N, 07°E） and Billerica （43°N, 71°W） respectively. The results agree very well with typical events observed at the three stations and can be used to explain some average features of negative phase ionospheric storms in middle latitudes.
基金the National Natural Science Foundation of China(Grant No.40134020)NKBRSF(Grant No.G2000078407)
文摘A theoretical model for ionospheric electric fields at mid- and low-latitudes is developed. In the geomagnetic dipolar coordinate system, we deduce a partial differential equation of electric potential from the ionospheric dynamo theory. The deduced equation is taken as the fundamental equation for the present model. The principal parameters for the model input, the thermospheric neutral winds, the densities and temperatures of electrons, ions and neutral atoms and molecules, are obtained from the empirical models HWM93, IRI90 and MSISE90, respectively. In terms of the relaxation iteration method, the partial equations for electric potential are solved successfully, and then, the ionospheric electric potential, fields, and currents are derived. Our model can reproduce the main features of the ionospheric electrodynamical processes such as the equatorial electric jet (EEJ), so it will be a useful tool for studying the upper atmosphere and ionosphere.
文摘E层占优电离层是指E层的峰值电子密度大于F层的峰值电子密度(NmE>NmF)时的电离层,记为ELDI(E-Layer Dominated Ionosphere)。针对ELDI,利用2007—2010年的COSMIC(Constellation Observing System for Meteorolo-gy,Ionosphere,and Climate satellite)掩星数据,在修正地磁纬度-磁地方时标系下统计分析了它在南北极区极夜期间(南北半球的冬至日前后30天)的分布特征,结果表明极夜期间电离层ELDI特征明显,其分布与极光椭圆位形基本一致,而且其在夜侧的发生率较高,特别是磁子夜之后,北极为70%左右,而南极为90%左右;另外南极的ELDI特征在磁纬度分布上要略宽于北极的分布范围。在ELDI高发区,电离层峰值电子密度要高于其两侧地区,特别是在夜侧,尤其是磁子夜前的峰值电子密度要接近甚至大于磁正午的峰值电子密度,在南极地区格外明显;而且ELDI高发区内的E层的电子含量(TECE)、电离层总电子含量(TECI)及TECE占TECI的比重(TECEI)都高于其两侧地区,北极TECE和TECI大于南极,而TECEI则是南极大于北极。这些现象主要是由于极夜期间极区高能粒子沉降引起底部电离层电离率增大所致;同时,由于地磁轴偏离地理轴的程度在南极要大于北极,使得极夜期间南极地区的电离层的电子密度,特别是在F层要相应地小于北极地区,从而导致了极夜期间南北半球极区电离层ELDI特征之间差异。
文摘SAMI2(Sami2 is Another Model of the Ionosphere)是美国海军实验室开发的电离层物理模型.利用该物理模型,模拟了东亚扇区不同太阳活动强度、不同纬度地区三个站的电离层电子浓度总含量(TEC).通过模拟结果与GPS观测站TEC数据的比较,检验SAMI2在此扇区的电离层TEC计算精度.结果表明,物理模型输出的电离层TEC具备与观测数据一致的周日变化、季节变化,太阳活动变化.周日分布上,上午时段SAMI2 TEC与观测数据吻合度优于午后时段;季节分布上,SAMI2 TEC在冬季与观测值偏差小于其他季节;SAMI2 TEC与GPS TEC相关系数各站均达到0.87以上,与赤道地区Guam站相关性最好;太阳活动低年计算结果优于太阳活动高年;多数情况下,SAMI2 TEC相对GPS TEC偏大.本文结果为基于SAMI2模型构建背景误差分布特征,开展该区域电离层数值预报研究可行性提供了理论支持.
