Modulation of ionospheric outflow ions by EMIC waves in the dayside outer magnetosphere

Abstract

Cold ions of the ionospheric origin mainly contribute to the ion population in the Earth's magnetosphere. These cold ions can be modulated by Pc5 ultralow frequency waves or wake electric fields in the dayside outer magnetosphere, through which their energy can increase to hundreds of eV. Using measurements of Magnetospheric Multiscale mission, this paper reports a new finding of the cold ion modulation process, occurring at a timescale of several seconds. This modulation is identified to be mainly controlled by large-amplitude electromagnetic ion cyclotron (EMIC) waves through the wave-induced electric field drift. This study also gives distinct observational features in the cold ion modulation processes associated with EMIC waves and wake electric fields.