09:45 〜 10:00
[PEM11-04] Temporal evolution of three-dimensional structures of metal ion layer around Japan simulated by mid-latitude ionospheric model
キーワード：スポラディックE層、シミュレーション、電離圏、金属イオン、中緯度
A numerical local ionospheric model with neutral winds of GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy) is used to investigate temporal evolutions of three-dimensional structures of metal ion layer (MIL) around Japan. The MILs appear especially in the ionospheric E region, which is called sporadic E, and show complicated structures such as multi-layer structures and intense density variation. Wind shear theory is recognized as the basic formation mechanism of the MILs, but it does not explain fully physical mechanism of the three-dimensional MIL structures, especially their sporadic behaviors. In the presentation, we present two simulation cases where the monthly averaged and the day-to-day variable wind effects on the MILs around Japan are investigated and classify temporal evolutions of complicated MIL structures in following four phases: (1) Above 110 km, MILs are generally constrained vertically and horizontally at zonal-wind shear null. (2) Below 110 km, MILs lag behind the zonal-wind shear null, and the three-dimensional MIL structures are affected not only by the wind shears but also the magnitude and direction of the horizontal winds. (3) When stagnating MILs exist below descending MILs, some ions of the stagnating MILs ascend and merge with the descending MILs, causing density enhancement of the descending MILs. (4) MILs stagnate around 100 km or descend to < 100 km depending on the strength of the vertical winds. Our result reveals that Phases (2)–(4) are crucial for the formation of the complicated MIL structures. Moreover, MIL tends to drift westward in the all phases because they tends to move with westward phase propagation of the migrating tides in Phase (1) and is embed in the westward wind regions in Phases (2)–(4).