磁暴期间太阳风-磁层-电离层间的耦合过程

本文用行星际和地面磁场以及电离层资料,讨论了三次磁暴期间高、中纬电离层电场对太阳风和磁层内变化的响应。 分析表明,当IMF的B_x分量由北向转为南向时,太阳风驱动的磁层对流变化能直接反映出高纬电离层电位的变化。但持续南向的B_x再次增强时,太阳风输入的主要能量耗损于内磁层过程;电离层的响应表现为一个弛豫过程。当B_x由南转北时,环电流的消失对电离层的作用同样有弛豫的特点。此时,驱动电位已撤消,环电流是维持电离层电位的唯一外源。 本文用电路类比及简单模式法结论对上述几种实测情况进行了讨论。

THE SOLAR WIND-MAGNETOSPHERE-IONOSPHERE COUPLING DURING MAGNETIC STORM

The indices of IMF, ground magnetic field and observations of ionospheric E-field are used to study the response of E-field in high and middle latitude ionosphere to variation of the solar wind and the magnetosphere. It is shown that although the electrostatic potential distribu-tion at the magnetopause driven by the solar wind can be directly mapped to the ionosphere along the magnetic field line to the polar cap boundary, the response of the ionospheric E-field at high and middle latitudes is a kind of relaxation process related to the existence and development of the ring current.During the sudden southward turning of Bz, usually the ring current does not exist, or is very weak. There is a direct response in ionospheric ETfield. Within the period of southward Bz, however, when |Bz| increases, the response of the ionospheric E-field is a retarded one, because a large amount of the driving energy of the solar wind would be expended on supporting the inner magnetospheric process to enhance the ring current.When a southward Bz suddenly turns northward, the decay of the ring current, just like it's formation and increasing, needs certain relaxation time. Since the driving potential does, not exist now, the so-called region 2 field-aligned current caused by the discharge of the polarization of the ring current, becomes the unique source of the potential in the ionosphere.Some insight into the observed processes may be obtained from the circuit analogy and the simple model.