Temporal Evolution of Three‐Dimensional Structures of Metal Ion Layer Around Japan Simulated by a Midlatitude Ionospheric Model

A regional numerical ionospheric model with neutral winds, corresponding to the Ground-to-topside of Atmosphere and Ionosphere for Aeronomy model, was used investigate temporal evolution 3-D structures metal ion layers (MILs) around Japan. The MILs that appear specifically in E region, called “sporadic E,” display complicated multi-layer intense density variations. Although wind shear theory elucidates basic formation mechanism MILs, it does not fully explain physical MIL structures, especially their sporadic behavior. Herein, we present two simulation cases which effect monthly mean day-to-day variations on Japan investigated. evolutions were classified into following four phases: (1) Above 110 km, are generally constrained vertically horizontally at zonal-wind null. (2) Below lag behind null, affected only by shears but also magnitude direction horizontal winds. (3) When stagnating ions exist below a descending MIL, some ascend merge thereby increasing its density. (4) stagnate 100 km or descend <100 depending strength vertical Our results reveal Phases (2–4) crucial structures.