Variations of Poynting Flux in the Northern Hemisphere during Quiet Times

Poynting flux energy is deposited from the magnetosphere in high latitudes, and measures the electromagnetic energy transmitted between the magnetosphere and the ionosphere. Little attention has been paid on the seasonal variation of the longitudinal pattern of the Poynting flux. Here, using long-term measurements of the ion drifts and the magnetic field by the DMSP satellite in the topside ionosphere, a statistical investigation of the longitudinal distributions of the Poynting flux in polar region during quiet times is conducted. Both case study and statistics show that there is a local maximum in downward Poynting flux in the pre-noon sector. Generally, the maximum is centered around geographic longitude of 120° west and geographic latitude of 80°, meaning that the total energy transferred into the ionosphere is the greatest in this region. The longitudinal distribution of the Poynting flux also exhibit clear seasonal variations with the longitudinal asymmetry the most significant in norther summer. The results could provide some new sights in future investigations of magnetosphere-ionosphere coupling in the polar region with observations and simulations.