太阳风向磁层-电离层(Magnetosphere and Ionosphere,MI)系统输入能量,而输入的能量随后在MI系统中消耗.本文从能量守恒原理出发,讨论太阳风-磁层-电离层(SMI)耦合过程中的能流路径和能量收支的定量关系.主要讨论9个问题:(1)太阳风向MI...太阳风向磁层-电离层(Magnetosphere and Ionosphere,MI)系统输入能量,而输入的能量随后在MI系统中消耗.本文从能量守恒原理出发,讨论太阳风-磁层-电离层(SMI)耦合过程中的能流路径和能量收支的定量关系.主要讨论9个问题:(1)太阳风向MI系统的能量输入,(2)MI系统对能量输入的响应,(3)环电流的能量消耗,(4)极区电离层焦耳加热的能量消耗,(5)极光粒子沉降的能量消耗,(6)磁尾能量的消耗、储存以及返回下游太阳风,(7)平静期间的能量积累与释放,(8)能量在不同能汇中的分配,(9)评价能量函数的准则和方法.展开更多
This paper presents a brief summary of our recent work based on global MHD simulations of the Solar wind-Magnetosphere-Ionosphere (SMI) system with emphasis on the electrodynamic coupling in the system.The main conclu...This paper presents a brief summary of our recent work based on global MHD simulations of the Solar wind-Magnetosphere-Ionosphere (SMI) system with emphasis on the electrodynamic coupling in the system.The main conclusions obtained are summarized as follows.(1) As a main dynamo of the SMI system,the bow shock contributes to both region 1 Field-Aligned Current (FAC) and cross-tail current.Under strong interplanetary driving conditions and moderate Alfv'en Mach numbers,the bow shock's contribution may exceed more than fifty percent of the total of either region 1 or cross-tail currents.(2) In terms of more than 100 simulation runs with due southward Interplanetary Magnetic Field (IMF),we have found a combined parameter f=E sw P sw M A -1/2 (E sw,P sw,and M A are the solar wind electric field,ram pressure,and Alfv'en Mach number,respectively):both the ionospheric transpolar potential and the magnetopause reconnection voltage vary linearly with f for small f,but saturate for large f.(3) The reconnection voltage is approximately fitted by sin 3/2 (θ IMF /2),where θ IMF is the IMF clock angle.The ionospheric transpolar potential,the voltage along the polar cap boundary,and the electric fields along the merging line however defined they may be,respond differently to θ IMF,so it is not justified to take them as substitutes for the reconnection voltage.展开更多
收敛速度慢一直是限制精密单点定位(precise point positioning,PPP)发展的重要因素。研究表明,通过高精度电离层延迟改正,进而实现精密单点定位实时动态(PPP-real time kinematic,PPP-RTK),可显著提升PPP的收敛速度。目前区域PPP-RTK...收敛速度慢一直是限制精密单点定位(precise point positioning,PPP)发展的重要因素。研究表明,通过高精度电离层延迟改正,进而实现精密单点定位实时动态(PPP-real time kinematic,PPP-RTK),可显著提升PPP的收敛速度。目前区域PPP-RTK中电离层主要采用单星多项式电离层模型(satellite-based ionospheric model with polynomial function,SIM_POLY)与单星电离层延迟反距离内插模型(satellite-based ionospheric model with inverse distance weight function,SIM_IDW)进行建模。为了检验上述两种模型在不同纬度的建模精度,对中国广东、湖北及河北3个省上空电离层延迟进行建模,并将其应用于单/双系统、浮点解及固定解中,分析其定位性能。实验结果表明,在低纬度区域,SIM_IDW模型表现略优于SIM_POLY模型,中高纬度区域则并无显著差异。浮点解PPP中,将SIM_IDW模型及SIM_POLY模型改正下的结果与无电离层组合PPP(ionosphere-free combination PPP,IFPPP)及欧洲定轨中心(Centre for Orbit Determination in Europe,CODE)的全球电离层格网(global ionospheric map,GIM)改正下的非差非组合结果进行比较,发现区域电离层模型改正下的PPP定位效果更好;与湖北省及广东省定位结果相比,河北省数据收敛速度最快,单GPS解算模式下采用SIM_IDW及SIM_POLY模型改正下的定位精度相较于IFPPP分别提升了43.7%和43.0%。固定解PPP中,河北省GPS+北斗解算模式下SIM_IDW、SIM_POLY模型改正下的PPP-RTK首个历元模糊度固定成功率分别可达86.09%和89.13%,且水平方向定位精度首个历元收敛至5 cm,高程方向定位精度1.5 min内收敛至10 cm;定位精度方面,在引入北斗系统之后,双系统PPP-RTK相较于单GPS有明显提升,河北省GPS+北斗解算模式下SIM_IDW、SIM_POLY模型改正下的PPP-RTK水平及三维定位精度分别为1.3 cm和3.5 cm。通过SIM_IDW及SIM_POLY模型建立区域电离层模型进而实现PPP-RTK,可以显著缩短PPP收敛时间,提高定位精度。展开更多
Dispersive Alfvén waves(DAWs)have been demonstrated to play a significant role in auroral generation of the magnetosphereionosphere coupling system.Starting from a two fluid reduced MHD model,we summarize the fre...Dispersive Alfvén waves(DAWs)have been demonstrated to play a significant role in auroral generation of the magnetosphereionosphere coupling system.Starting from a two fluid reduced MHD model,we summarize the frequency,temporal and spatial characteristics of magnetospheric DAWs.Then,the nonlinear kinetic and inertial scale Alfveén waves are studied,and we review some theoretical aspects and simulation results of dispersive Alfve′n waves in Earth's magnetosphere.It is shown that dispersive standing Alfve′n waves can generate the field-aligned currents which transport energy into the auroral ionosphere,where it is dissipated by Joule heating and energy lost due to electron precipitation.The Joule dissipation can heat the ionospheric electron and produce changes in the ionospheric Pedersen conductivity.As a feedback,the conducting ionosphere can also strongly affect the magnetospheric currents. The ponderomotive force can cause the plasma to move along the field line,and generate ionospheric density cavity.The nonlinear structuring can lead to a dispersive scale to accelerate auroral particle,and the Alfvn waves can be trapped within the density cavity. Finally,we show the nonlinear decay of dispersive Alfvén waves related to two anti-propagating electron fluxes observed in the auroral zone.展开更多
The energy budget of the magnetosphere-ionosphere (MI) system during 1998-2008 was examined by using Akasofu's epsilon function. The results showed that 1) the yearly average rate of solar wind energy input into t...The energy budget of the magnetosphere-ionosphere (MI) system during 1998-2008 was examined by using Akasofu's epsilon function. The results showed that 1) the yearly average rate of solar wind energy input into the MI system was 4.51 GGJ (GGJ=1018 J), while the yearly average total dissipation was 4.30 GGJ; 2) the energy partitioning in the ring current and polar region was 56%:44%; 3) the energy input and dissipation processes continuously proceeded both in storm-substorm events and less disturbed intervals, suggesting the significant contribution of slow but long-lasting energy process during the less disturbance periods to the total energy budget. In addition, we found in this study an interesting phenomenon "self-adjustment ability" of the MI system which behaves just like a water reservoir. During solar active years, the input energy is more than the dissipated energy, implying that a portion of the input energy is not immediately released, but is stored in the magnetosphere. On the other hand, during less active years, the dissipated energy is more than the input energy, implying that the previously stored energy makes up for the energy input shortage in this period.展开更多
文摘太阳风向磁层-电离层(Magnetosphere and Ionosphere,MI)系统输入能量,而输入的能量随后在MI系统中消耗.本文从能量守恒原理出发,讨论太阳风-磁层-电离层(SMI)耦合过程中的能流路径和能量收支的定量关系.主要讨论9个问题:(1)太阳风向MI系统的能量输入,(2)MI系统对能量输入的响应,(3)环电流的能量消耗,(4)极区电离层焦耳加热的能量消耗,(5)极光粒子沉降的能量消耗,(6)磁尾能量的消耗、储存以及返回下游太阳风,(7)平静期间的能量积累与释放,(8)能量在不同能汇中的分配,(9)评价能量函数的准则和方法.
基金Supported by grants NNSFC (40831060,40621003)NKBRSF G2006CB806304 in China
文摘This paper presents a brief summary of our recent work based on global MHD simulations of the Solar wind-Magnetosphere-Ionosphere (SMI) system with emphasis on the electrodynamic coupling in the system.The main conclusions obtained are summarized as follows.(1) As a main dynamo of the SMI system,the bow shock contributes to both region 1 Field-Aligned Current (FAC) and cross-tail current.Under strong interplanetary driving conditions and moderate Alfv'en Mach numbers,the bow shock's contribution may exceed more than fifty percent of the total of either region 1 or cross-tail currents.(2) In terms of more than 100 simulation runs with due southward Interplanetary Magnetic Field (IMF),we have found a combined parameter f=E sw P sw M A -1/2 (E sw,P sw,and M A are the solar wind electric field,ram pressure,and Alfv'en Mach number,respectively):both the ionospheric transpolar potential and the magnetopause reconnection voltage vary linearly with f for small f,but saturate for large f.(3) The reconnection voltage is approximately fitted by sin 3/2 (θ IMF /2),where θ IMF is the IMF clock angle.The ionospheric transpolar potential,the voltage along the polar cap boundary,and the electric fields along the merging line however defined they may be,respond differently to θ IMF,so it is not justified to take them as substitutes for the reconnection voltage.
文摘收敛速度慢一直是限制精密单点定位(precise point positioning,PPP)发展的重要因素。研究表明,通过高精度电离层延迟改正,进而实现精密单点定位实时动态(PPP-real time kinematic,PPP-RTK),可显著提升PPP的收敛速度。目前区域PPP-RTK中电离层主要采用单星多项式电离层模型(satellite-based ionospheric model with polynomial function,SIM_POLY)与单星电离层延迟反距离内插模型(satellite-based ionospheric model with inverse distance weight function,SIM_IDW)进行建模。为了检验上述两种模型在不同纬度的建模精度,对中国广东、湖北及河北3个省上空电离层延迟进行建模,并将其应用于单/双系统、浮点解及固定解中,分析其定位性能。实验结果表明,在低纬度区域,SIM_IDW模型表现略优于SIM_POLY模型,中高纬度区域则并无显著差异。浮点解PPP中,将SIM_IDW模型及SIM_POLY模型改正下的结果与无电离层组合PPP(ionosphere-free combination PPP,IFPPP)及欧洲定轨中心(Centre for Orbit Determination in Europe,CODE)的全球电离层格网(global ionospheric map,GIM)改正下的非差非组合结果进行比较,发现区域电离层模型改正下的PPP定位效果更好;与湖北省及广东省定位结果相比,河北省数据收敛速度最快,单GPS解算模式下采用SIM_IDW及SIM_POLY模型改正下的定位精度相较于IFPPP分别提升了43.7%和43.0%。固定解PPP中,河北省GPS+北斗解算模式下SIM_IDW、SIM_POLY模型改正下的PPP-RTK首个历元模糊度固定成功率分别可达86.09%和89.13%,且水平方向定位精度首个历元收敛至5 cm,高程方向定位精度1.5 min内收敛至10 cm;定位精度方面,在引入北斗系统之后,双系统PPP-RTK相较于单GPS有明显提升,河北省GPS+北斗解算模式下SIM_IDW、SIM_POLY模型改正下的PPP-RTK水平及三维定位精度分别为1.3 cm和3.5 cm。通过SIM_IDW及SIM_POLY模型建立区域电离层模型进而实现PPP-RTK,可以显著缩短PPP收敛时间,提高定位精度。
基金supported by the National Natural Science Foundation of China(40874087 and 41031063)the China Meteorological Administration(GYHY201106011)the China Public Science and Technology Research Funds Projects of Ocean(201005017)
文摘Dispersive Alfvén waves(DAWs)have been demonstrated to play a significant role in auroral generation of the magnetosphereionosphere coupling system.Starting from a two fluid reduced MHD model,we summarize the frequency,temporal and spatial characteristics of magnetospheric DAWs.Then,the nonlinear kinetic and inertial scale Alfveén waves are studied,and we review some theoretical aspects and simulation results of dispersive Alfve′n waves in Earth's magnetosphere.It is shown that dispersive standing Alfve′n waves can generate the field-aligned currents which transport energy into the auroral ionosphere,where it is dissipated by Joule heating and energy lost due to electron precipitation.The Joule dissipation can heat the ionospheric electron and produce changes in the ionospheric Pedersen conductivity.As a feedback,the conducting ionosphere can also strongly affect the magnetospheric currents. The ponderomotive force can cause the plasma to move along the field line,and generate ionospheric density cavity.The nonlinear structuring can lead to a dispersive scale to accelerate auroral particle,and the Alfvn waves can be trapped within the density cavity. Finally,we show the nonlinear decay of dispersive Alfvén waves related to two anti-propagating electron fluxes observed in the auroral zone.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40931056, 40874089)the National Basic Research Program of China ("973" Project) (Grant Nos. 2008CB425704)
文摘The energy budget of the magnetosphere-ionosphere (MI) system during 1998-2008 was examined by using Akasofu's epsilon function. The results showed that 1) the yearly average rate of solar wind energy input into the MI system was 4.51 GGJ (GGJ=1018 J), while the yearly average total dissipation was 4.30 GGJ; 2) the energy partitioning in the ring current and polar region was 56%:44%; 3) the energy input and dissipation processes continuously proceeded both in storm-substorm events and less disturbed intervals, suggesting the significant contribution of slow but long-lasting energy process during the less disturbance periods to the total energy budget. In addition, we found in this study an interesting phenomenon "self-adjustment ability" of the MI system which behaves just like a water reservoir. During solar active years, the input energy is more than the dissipated energy, implying that a portion of the input energy is not immediately released, but is stored in the magnetosphere. On the other hand, during less active years, the dissipated energy is more than the input energy, implying that the previously stored energy makes up for the energy input shortage in this period.
