Long term average distribution of $\mathrm{O}^{+}$ in the quiet-time terrestrial magnetosphere

Abstract

Cluster measurements from 2001 to 2011 provide a unique opportunity to study the characteristics of $\mathrm{O}^{+}$ with full spatial coverage between 4 to $19 \mathrm{R}_{E}$, especially in the mid-latitude region. Three-dimensional spatial distributions of averaged omnidirectional $\mathrm{O}^{+}$ differential fluxes in three energy channels (E1:40–136 eV; E2:136 eV–3 keV; E3:3–30 keV) during quiet times ($\mathit{Dst} > -20~\mbox{nT}$) are presented in this paper. Comparing the distributions of $\mathrm{O}^{+}$ in three energy channels helps us to better understand the transport and energization of $\mathrm{O}^{+}$. Consistent with previous studies, it is suggested that during quiet times $\mathrm{O}^{+}$ is heated in the high-altitude cusp and mantle, and part of this heated population is transported through the lobes to the plasmasheet, where it is further heated/accelerated. The distributions presented provide important background information for relevant simulation and observation studies of $\mathrm{O}^{+}$ behavior during storm and non-storm times.