Electromagnetic energy input and dissipation

Evaluation of the energy budget of the ionosphere-thermosphere (IT) is an important and challenging problem in geospace dynamics and magnetosphere-IT coupling. Correct representation of the energy budget indicates our understanding of underlying physical processes. Recent observations have highlighted the role of electromagnetic processes in energy input and dissipation in the high-latitude IT system. This chapter provides observational multiscale Poynting flux estimates and resource reference tables. Theoretical foundations for the definition of Joule heating and its estimation with first-principles global and empirical models will be overviewed in detail. The roles of quasistatic versus high-frequency fields, temporal and spatial resolutions in data, and model for estimating electromagnetic energy budget will be discussed. Challenges in understanding, inconsistencies in definitions, and future research directions for advancing our knowledge of multiscale Poynting flux and Joule heating will be outlined.