Читать книгу Space Physics and Aeronomy, Ionosphere Dynamics and Applications - Группа авторов - Страница 46

This chapter reviews recent findings of multi-scale structures and dynamics in the high-latitude ionosphere, particularly on meso-scale (10s‐100s km) processes, as well as their roles in cross-regional interaction processes. Localized and transient structures often occur at the cusp, polar cap, and auroral oval, and their magnitudes can be comparable or larger than those of large-scale background. However, their properties and coupling are not well understood, and specification of their structures and variabilities are critical for numerical modeling. The meso-scale covers a myriad processes and phenomena, including poleward-moving auroral forms (PMAFs), polar cap patches, auroral arcs, poleward boundary intensifications (PBIs), streamers, substorm, surges, diffuse aurora, and related flow channels, field-aligned currents (FACs) and precipitation/conductance. Small‐scale features also play important roles in the creation and behavior in multi-scale dynamics. While those structures are localized, they have net effects on large-scale dynamics, and can influence surrounding regions by propagating over long distances. An approach to quantify meso-scale precipitation contributions using the THEMIS all‐sky imagers is presented, and we show that meso-scale precipitation has a substantial (25‐50%) contribution, indicating critical importance of multi-scale processes for understanding Geospace processes. The current state and necessity of specification for advancing understanding of multi-scale coupling processes are discussed.