磁暴期电离层离子上行能通量的统计关系研究

Statistical Relationships between Ionospheric Upflows and Various Parameters during Geomagnetic Storms

利用FAST卫星1997—2006年34个磁暴期149个轨道的观测数据,分析不同相位上行通量数量级,研究不同相位离子上行能通量与地磁活动Sym-H指数和Kp指数,以及注入的Poynting通量之间的关系,构造上行通量经验模型。研究结果表明:磁暴主相期间,上行离子能通量可超过10^(8) eV·cm^(-2)·s^(-1)·sr^(-1)·eV^(-1)量级,初相和恢复相期,上行离子能通量可超过107 eV·cm^(-2)·s^(-1)·sr^(-1)·eV^(-1)量级,主相期能通量均值普遍高于初相和恢复相;磁暴初相期间,上行离子能通量与Sym-H、/p以及Poynting通量成显著正相关,相关系数分别为0.890、0.664和0.660;磁暴主相期间相关系数分别为0.858、0.823和0.541。以磁暴主相为例,上行离子能通量与Sym-H和Poynting通量的经验公式为J_(i+)=10^(5.324±0.581)×(Sym-H)^(1.465±0.340),J_(i+)=10^(6.469±0.798)×S_(dc)^(0.888±0.703)。初相期间,由于地磁扰动时能量快速注入,电离层离子迅速获能,上行离子能通量与地磁扰动指数呈现较高的相关性,同时主相期上行离子能通量的增幅跨越两个量级;向下的Poynting通量导致的焦耳耗散是离子获能的重要来源之一,因此上行离子能通量与Poynting通量有较强的相关性。恢复相期间地磁活动趋于平静,上行离子能通量低于主相期的能通量。

A collection of data from 149 orbits by the Fast Auroral SnapshoT(FAST)mission during 34 geomagnetic storms from 1997 to 2006 is used to analyze the energy flux of upflowing ions as a function of storm phases,and analyze the relationships between the flux and the parameters,including Sym-H index,Kp index,and the Poynting flux to construct empirical models.Results show that,in the main phase of the storm,the energy flux exceeds 10^(8) eV·cm^(-2)·s^(-1)·sr^(-1)·eV^(-1),and in the initial and recovery phases,the energy flux can exceed 10^(7) eV·cm^(-2)·s^(-1)·sr^(-1)·eV^(-1).The averaged energy flux in the main phase is higher than that in the initial and recovery phases.In the initial phase,the flux is significantly positively correlated to Sym-H,Kp and the Poynting flux.The correlation coefficients are 0.890,0.664 and 0.660,respectively.In the main phase,the correlation coefficients are 0.858,0.823 and 0.541,respectively.Empirical formulas for the energy flux as functions of the Sym-H and the Poynting flux are constructed.In the main phase,J_(i+)=10^(5.324±0.581)×(Sym-H)^(1.465±0.340),J_(i+)=10^(6.469±0.798)×S_(dc)^(0.888±0.703).In the initial phase,due to the rapid injection of the energy during geomagnetic disturbance and the rapid energy acquisition of ionospheric ions,the ion energy flux is highly correlated with the geomagnetic disturbance indices.Meanwhile,the energy flux increases by two orders of magnitude in the main phase.The Joule dissipation caused by the downward Poynting flux is one of the important sources of ion energy acquisition,and a strong correlation is observed.