国际参考电离层模型IRI(the international reference ionosphere model)是利用全球电离层测站以及卫星观测数据建立的电离层经验模型,并广泛用于电离层研究领域.本文选用2014年地磁暴平静期的IRI-2016模式和电离层垂测仪的数据,对电离...国际参考电离层模型IRI(the international reference ionosphere model)是利用全球电离层测站以及卫星观测数据建立的电离层经验模型,并广泛用于电离层研究领域.本文选用2014年地磁暴平静期的IRI-2016模式和电离层垂测仪的数据,对电离层F2层峰值电子密度NmF2和峰值高度HmF2两个物理量,通过IRI模型最新版本(IRI-2016)在地磁环境平静期的误差精度进行评估.根据不同磁倾角范围分别选择5个台站(Juliusruh(54°N,13°E)磁倾角:68.54°,Okinawa(26°N,128°E)磁倾角:37.26°,Jicamarca(12°S,77°W)磁倾角:-0.26°,Port_Stanley(52°S,58°W)磁倾角:-51.20°,Hermanus(34°S,19°E)磁倾角:-64.24°)进行NmF2和HmF2参数对比分析.5个台站中Port_Stanley站的NmF2相关性最差(相关系数0.68),Okinawa站HmF2相关性最差(相关系数0.52),Juliusruh站两个参数的相关性最高(相关系数0.87).以Juliusruh站为例进行白昼、夜晚以及不同季节的分析,可以看出白昼误差明显低于夜晚,相较于分季(春或秋)和冬季,IRI模型在夏季预测效果最好.5个台站的研究结果表明,IRI模型与垂测仪数据具备一致性,IRI模型的值高于实测数据值.展开更多
TIEGCM(Thermosphere-Ionosphere-Electrodynamics General Circulation Model)是NCAR/HAO(The High Altitude Observatory at the National Center for Atmospheric Research)开发的一个三维时变全球尺度电离层-热层耦合数值模式.我们...TIEGCM(Thermosphere-Ionosphere-Electrodynamics General Circulation Model)是NCAR/HAO(The High Altitude Observatory at the National Center for Atmospheric Research)开发的一个三维时变全球尺度电离层-热层耦合数值模式.我们将该模式的输出参数hmF2与经验模式国际参考电离层(International Reference Ionosphere,IRI)-2016的结果以及中国地区12个电离层测高仪的hmF2观测数据进行了对比,给出了TIEGCM模式在地磁活动平静条件下中国区域不同季节的预测性能分析.总体来看,TIEGCM模式在所有观测站都表现良好,一定程度上能很好地进行中国区域电离层hmF2参量研究.且TIEGCM模拟电离层变化的性能比IRI要高25%左右,能在一定程度上进行电离层半年异常和赤道异常模拟.但无论是与IRI模型还是与观测相比,TIEGCM模式均存在一定的误差.并且误差在低纬地区以及日出日落时段波动较大,这些结果为我们以后进行潜在的模式精度控制提供了理论依据.展开更多
This study is a contribution to the estimation of the winter anomaly in the F2 layer of the ionosphere at low latitudes. The aim is to study the variability of the virtual height (hmF2) of the F2 region of the ionosph...This study is a contribution to the estimation of the winter anomaly in the F2 layer of the ionosphere at low latitudes. The aim is to study the variability of the virtual height (hmF2) of the F2 region of the ionosphere through the predictions of the latest International Reference Ionosphere model (IRI-2016). The present work allows analyzing the temporal evolution of hmF2 according to the different phases of three (3) solar cycles during the quiet geomagnetic activity to estimate the seasonal anomaly at the Ouagadougou station. The analysis of the seasonal profiles shows that the variability of hmF2 is: 1) strongly linked to the solar cycle activity, 2) dependent on the season and 3) variable from one cycle to the next for the same phase. It appears that hmF2 increases during the ascending phase to reach its maximum value at the phase maximum. During the descending phase, it decreases until the phase minimum where it finds its minimum value. The difference between winter and summer on the hmF2 values for each phase of the cycle is obtained at the phase minimum and is estimated to be at least 16 km. In low latitudes, solar irradiation is greater in summer than in winter. From this study, hmF2 values are larger in winter compared to summer indicating an anomaly in the virtual height of the F2 layer of the ionosphere through the predictions of IRI-2016 at the Ouagadougou station.展开更多
A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the de...A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.展开更多
The ionospheric scale height around the peak height of F2 layer(HmF2)is a very important parameter defining the profile of topside ionosphere.Based on observations of the EISCAT ESR radar,we statistically study the Hm...The ionospheric scale height around the peak height of F2 layer(HmF2)is a very important parameter defining the profile of topside ionosphere.Based on observations of the EISCAT ESR radar,we statistically study the HmF2 at high latitudes.In order to derive the HmF2,a least square method is adopted to fit the electron density profile above the peak height of F2 layer(hmF2)from observations of the ESR radar.The result shows that it is in well agreement between the topside profiles deduced from the fitted HmF2 and the actual measuring topside profile with a height range from hmF2 to 300 km above the hmF2.Therefore,HmF2 can be considered as a constant in this range.With observations of the ESR between 1997 and 2008,we analyze the statistical characteristics of polar HmF2 with local time,season,and solar activity under quiet geomagnetic conditions(Kp≤2),respectively.Variations of HmF2 in quiet days show a diurnal trend with a maximum in the morning and a minimum in the afternoon.The HmF2 always has the highest seasonal amplitude in summer under three kinds of solar activities.The seasonal magnitude of the HmF2 in winter remains between that in spring and that in autumn under low solar activity,while it is the lowest under moderate and high solar activities.We also compare measured HmF2 with those derived by IRI2007,which indicates that IRI2007 model can only approximately provide the average values of polar HmF2 in quiet days but is limited in presenting diurnal and solar activity variations of HmF2.展开更多
文摘国际参考电离层模型IRI(the international reference ionosphere model)是利用全球电离层测站以及卫星观测数据建立的电离层经验模型,并广泛用于电离层研究领域.本文选用2014年地磁暴平静期的IRI-2016模式和电离层垂测仪的数据,对电离层F2层峰值电子密度NmF2和峰值高度HmF2两个物理量,通过IRI模型最新版本(IRI-2016)在地磁环境平静期的误差精度进行评估.根据不同磁倾角范围分别选择5个台站(Juliusruh(54°N,13°E)磁倾角:68.54°,Okinawa(26°N,128°E)磁倾角:37.26°,Jicamarca(12°S,77°W)磁倾角:-0.26°,Port_Stanley(52°S,58°W)磁倾角:-51.20°,Hermanus(34°S,19°E)磁倾角:-64.24°)进行NmF2和HmF2参数对比分析.5个台站中Port_Stanley站的NmF2相关性最差(相关系数0.68),Okinawa站HmF2相关性最差(相关系数0.52),Juliusruh站两个参数的相关性最高(相关系数0.87).以Juliusruh站为例进行白昼、夜晚以及不同季节的分析,可以看出白昼误差明显低于夜晚,相较于分季(春或秋)和冬季,IRI模型在夏季预测效果最好.5个台站的研究结果表明,IRI模型与垂测仪数据具备一致性,IRI模型的值高于实测数据值.
文摘TIEGCM(Thermosphere-Ionosphere-Electrodynamics General Circulation Model)是NCAR/HAO(The High Altitude Observatory at the National Center for Atmospheric Research)开发的一个三维时变全球尺度电离层-热层耦合数值模式.我们将该模式的输出参数hmF2与经验模式国际参考电离层(International Reference Ionosphere,IRI)-2016的结果以及中国地区12个电离层测高仪的hmF2观测数据进行了对比,给出了TIEGCM模式在地磁活动平静条件下中国区域不同季节的预测性能分析.总体来看,TIEGCM模式在所有观测站都表现良好,一定程度上能很好地进行中国区域电离层hmF2参量研究.且TIEGCM模拟电离层变化的性能比IRI要高25%左右,能在一定程度上进行电离层半年异常和赤道异常模拟.但无论是与IRI模型还是与观测相比,TIEGCM模式均存在一定的误差.并且误差在低纬地区以及日出日落时段波动较大,这些结果为我们以后进行潜在的模式精度控制提供了理论依据.
文摘This study is a contribution to the estimation of the winter anomaly in the F2 layer of the ionosphere at low latitudes. The aim is to study the variability of the virtual height (hmF2) of the F2 region of the ionosphere through the predictions of the latest International Reference Ionosphere model (IRI-2016). The present work allows analyzing the temporal evolution of hmF2 according to the different phases of three (3) solar cycles during the quiet geomagnetic activity to estimate the seasonal anomaly at the Ouagadougou station. The analysis of the seasonal profiles shows that the variability of hmF2 is: 1) strongly linked to the solar cycle activity, 2) dependent on the season and 3) variable from one cycle to the next for the same phase. It appears that hmF2 increases during the ascending phase to reach its maximum value at the phase maximum. During the descending phase, it decreases until the phase minimum where it finds its minimum value. The difference between winter and summer on the hmF2 values for each phase of the cycle is obtained at the phase minimum and is estimated to be at least 16 km. In low latitudes, solar irradiation is greater in summer than in winter. From this study, hmF2 values are larger in winter compared to summer indicating an anomaly in the virtual height of the F2 layer of the ionosphere through the predictions of IRI-2016 at the Ouagadougou station.
基金Project(2010DFA41440)supported by China-Japan International CooperationProject(2016TP1007)supported by the Hunan Provincial Science and Technology Plan,ChinaProject(21376269)supported by the National Natural Science Foundation of China
文摘A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.
基金The National Natural Science Foundation of China (Grant Nos. 41174140, 41221003 and 41374168)The Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20110141110043)+1 种基金Chinese Academy of Sciences, Program for New Century Excellent Talents in University (Grant No. NCET-13-0446)The Fundamental Research Funds for the Central Universities (Grant No. 2012212020206)
文摘The ionospheric scale height around the peak height of F2 layer(HmF2)is a very important parameter defining the profile of topside ionosphere.Based on observations of the EISCAT ESR radar,we statistically study the HmF2 at high latitudes.In order to derive the HmF2,a least square method is adopted to fit the electron density profile above the peak height of F2 layer(hmF2)from observations of the ESR radar.The result shows that it is in well agreement between the topside profiles deduced from the fitted HmF2 and the actual measuring topside profile with a height range from hmF2 to 300 km above the hmF2.Therefore,HmF2 can be considered as a constant in this range.With observations of the ESR between 1997 and 2008,we analyze the statistical characteristics of polar HmF2 with local time,season,and solar activity under quiet geomagnetic conditions(Kp≤2),respectively.Variations of HmF2 in quiet days show a diurnal trend with a maximum in the morning and a minimum in the afternoon.The HmF2 always has the highest seasonal amplitude in summer under three kinds of solar activities.The seasonal magnitude of the HmF2 in winter remains between that in spring and that in autumn under low solar activity,while it is the lowest under moderate and high solar activities.We also compare measured HmF2 with those derived by IRI2007,which indicates that IRI2007 model can only approximately provide the average values of polar HmF2 in quiet days but is limited in presenting diurnal and solar activity variations of HmF2.
