[P-EM15] 太陽地球系結合過程の研究基盤形成

[PEM15-05] The Causality of Electromagnetic Channel Formation in the Ionosphere from Polar to Equatorial Regions

*吉川 顕正¹ (1.九州大学大学院理学研究院地球惑星科学部門)

キーワード：電磁チャンネルの形成、電離層電流、電磁プロセス

The formation of the global ionospheric current systems and their associated plasma dynamics are frequently discussed under the electrostatic approximation of plasma electrodynamics. Since the Poynting flux never across the equipotential line, it is impossible to provide electromagnetic energy from the source region to the loading region across the magnetic field line. And hence, to discuss causality for the evolution of the ionospheric current system, we need to take into account an electromagnetic process of the coupled system. To resolve this problem, we propose an electromagnetic coupling model from the polar to the equatorial ionosphere. In this model, ionospheric current produces Ampere force and generates the motion of plasma. The motion of plasma and associated mechanical processes excite electromotive force and the resultant electric field. The Curl of the electric field causes magnetic field disturbances and the evolution of ionospheric current. Therefore, causality for the evolution of electromagnetic energy and plasmas acceleration for expanding of the ionospheric current system has occurred at the wavefront region and/or conductivity gradient region. In this talk, we will discuss what type of plasma motion induces an electric field in the ionosphere, and how and where they produce magnetic field disturbances (hence the Ampere force) for an acceleration of plasma as a wave propagation process. Furthermore, we also discuss what kind of mechanical and electromagnetic processes have occurred at the conductivity gradient region, which becomes very important for the establishment of the geometrical structure of the ionospheric current system.