Efficiency of Electromagnetic Energy Transfer From Solar Wind to Ionosphere Through Magnetospheric Ultra-Low Frequency Waves

Ultra-low frequency (ULF) waves are a ubiquitous carrier of energy in geospace. However, their efficiency in transferring solar wind energy into the upper atmosphere remains a fundamental and not well-understood question. This is due to their global presence, which cannot be fully quantified by spatially limited observations, and the need for self-consistent global modeling to account for their dependence on dynamic, inhomogeneous magnetic fields and plasma densities. In this study we use a purely global magnetohydrodynamic model to investigate energy inputs to the ionosphere in the form of Poynting flux. Oscillations in solar wind dynamic pressure excite field line resonances in the magnetosphere. The total Alfvénic Poynting flux entering the ionosphere can be comparable to the total quasi-steady Poynting flux under northward interplanetary magnetic field. The efficiency of this energy transfer via ULF waves depends on the driving frequency of the solar wind and the ionospheric Pedersen conductance.