Research on thegeneration mechanisms of ion upflow in the polar cap ionosphere by using ESR.

利用ESR研究极帽电离层离子上流产生机制

• 批准号: 11440144
• 负责人: FUJII Ryoichi
• 金额: $ 9.34万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440144/
• 关键词: ion outflow; ion heating; polar cap region; auroral zone; high latitude ionosphere; Svalbard EISCAT radar; EISCAT radar; IS spectra

By using EISCAT radars together with satellites, we have investigated mainly three aspects of ion upflow phenomena in order to understand the generation mechanisms of ion up flow. The first step was to investigate the relationship between ion upflow and particle precipitation which is different between several magnetospheric regions. The second step was to investigate the relationship between ion upflow and heating, from the macroscopic point of view. The third step was to investigate the characteristics of naturally enhanced ion-acoustic lines (NEIALs), which may be caused by plasma instabilities and are strongly related to ion upflow from the microscopic point of view. We have examined the regions where dayside field-aligned (FA) ion upflows occur, based on a statistical analysis using approximately 170 simultaneous events between the ESR and the DMSP satellites. This systematic analysis for ion upflow has never been examined. We found that ion up flows occur not only in the cusp and … More cleft (the low altitude portion of the low-latitude boundary layer (LLBL)) which have been considered as ion up flow regions, but also in the topside ionosphere connected to the mantle region. Ion upflows seldom occur either in the Boundary Plasma Sheet (EPS) or in the Central Plasma Sheet (CPS) in the dayside high latitudes. Almost all of the events in which the average FA ion velocity is more than 100 m s^<-1> are associated with sufficient soft electron precipitation (differential energy flux of electrons at 100 eV > 10^7 eV cm^<-2> s^<-1> sr^<-1> eV^<-1>). Although soft electron precipitation also sufficiently exists in the EPS, the ion velocities are mostly less than 100 m s^<-1>. The present results indicate that soft particle precipitation is the predominant energy source driving ion up flow in the topside ionosphere, but it works on ion upflow effectively in the higher latitude regions in the dayside and not in the EPS. In addition, plasma heating associated with FA ion upflow in the daysjde topside ionosphere has been examined using data obtained simultaneously with the ESR and the EISCAT VHP radar, and also the wave number (k)-dependence of the received power in high signal-to-noise ratio (SNR) conditions, occurring for NEIALs and for real satellites, has been investigated.The results from these three investigations lead to the conclusion that the energy of soft electron precipitation is considered as the main source of the ion up flow. The energy of soft particle precipitation is supplied to the ions in the topside ionosphere via wave-particle interaction, such as wave-induced transverse ion heating, and upward parallel electric field due to anomalous resistively produced by plasma turbulence. Thus generation mechanisms of ion upflow must have the transversely ion heating and the upward acceleration by wave-particle interaction while the induced plasma waves decay. In addition to direct precipitation effects, namely enhanced ambipolar diffusion and heat flux, wave-particle interaction may hence play an important role in driving ion upflow. Less

为了了解离子上升流的产生机理，我们利用EISCAT雷达和卫星对离子上升流现象进行了三个方面的研究。第一步是研究不同磁层区域的离子上涌与粒子沉淀之间的关系。第二步是从宏观角度研究离子上涌与加热之间的关系。第三步是研究自然增强离子声线（neial）的特征，这可能是由等离子体不稳定性引起的，从微观角度来看与离子上涌密切相关。根据ESR和DMSP卫星之间大约170个同时发生的事件的统计分析，我们研究了日侧场对准（FA）离子上升发生的区域。这种对离子上涌的系统分析从未被检验过。我们发现离子上升流动不仅发生在被认为是离子上升流动区域的尖峰和断裂带（低纬边界层（LLBL）的低海拔部分），而且还发生在与地幔区相连的上层电离层。在日侧高纬度地区，边界等离子体片（EPS）和中央等离子体片（CPS）都很少发生离子上升。几乎所有FA离子平均速度大于100 m s^<-1>的事件都与充分的软电子沉淀有关（电子在100 eV >时的差能通量为10^7 eV cm^<-2> s^<-1> sr^<-1> eV^<-1>）。虽然软电子沉淀在EPS中也充分存在，但离子速度大多小于100 m s^<-1>。结果表明，软粒子降水是驱动上层电离层离子上升流动的主要能量来源，但它在日侧高纬度地区对离子上升流动有效，而在EPS中不起作用。此外，利用ESR和EISCAT VHP雷达同时获得的数据，研究了与FA离子上升有关的等离子体加热，并研究了在高信噪比（SNR）条件下接收功率的波数(k)依赖性，发生在neal和真实卫星上。这三种研究结果表明，软电子沉淀能量是离子上升流动的主要来源。软粒子沉淀的能量是通过波粒相互作用提供给上层电离层的离子的，如波动引起的横向离子加热和等离子体湍流产生的异常电阻引起的向上平行电场。因此，离子上流的产生机制必须在诱导等离子体波衰减时具有离子的横向加热和波粒相互作用的向上加速作用。除了直接降水效应，即增强的双极扩散和热通量外，波粒相互作用可能在驱动离子向上流动中起重要作用。少

项目成果

Yoshida,Naofumi: "Coordinated Akebono and EISCAT observations of suprathermal ion outflows in the nightside inverted-V region"Journal of Atmospheric Solar-Terrestrial Physics. 62. 449-465 (2000)

吉田尚文：“曙光和 EISCAT 对夜侧倒 V 区超热离子流出的协调观测”《大气日地物理学杂志》。

Fujii, Ryoichi: "Field-aligned ion motions in the E and F regions"Journal Geophysical Rescearch. (in press). (2002)

Fujii, Ryoichi：“E 和 F 区域中的场对准离子运动”地球物理研究杂志。

Nagatsuma, T., et al.: "Higher latitude Pi3 pulsations observed by the EISCAT VHP radar"Adv. Space Res.. 27(8). 1429-1431 (2001)

Nagatsuma, T. 等人：“EISCAT VHP 雷达观测到的高纬度 Pi3 脉动”Adv.

Fujii, R., et al.: "Field-aligned ion motions in the E and F regions"J. Geophys. Res. (in press). (2002)

Fujii, R., et al.：“E 和 F 区域中的场对准离子运动”J。

Saito,Susumu: "Effects of kappa distribution electrons on incoherent scaner spectra."Annales Geophysicae. 18. 1216-1223 (2000)

Saito,Susumu：“卡帕分布电子对非相干扫描仪光谱的影响。”地球物理学年鉴。