Energetic ion distributions in the near-Earth plasma sheet can provide important information for understanding the entry of ions into the magnetosphere and their transportation, acceleration, and losses in the near-Earth region. In this study, 11 years of energetic proton and oxygen observations (> ~274 keV) from Cluster/Research with Adaptive Particle Imaging Detectors were used to statistically study the energetic ion distributions in the near-Earth region. The dawn-dusk asymmetries of the distributions in three different regions (dayside magnetosphere, near-Earth nightside plasma sheet, and tail plasma sheet) are examined in Northern and Southern Hemispheres. The results show that the energetic ion distributions are inﬂuenced by the dawn-dusk interplanetary magnetic ﬁeld (IMF) direction. The enhancement of ion intensity largely correlates with the location of the magnetic reconnection at the magnetopause. The results imply that substorm-related acceleration processes in the magnetotail are not the only source of energetic ions in the dayside and the near-Earth magnetosphere. Energetic ions delivered through reconnection at the magnetopause signiﬁcantly affect the energetic ion population in the magnetosphere. We also believe that the inﬂuence of the dawn-dusk IMF direction should not be neglected in models of the particle population in the magnetosphere.
Journal of Geophysical Research: Space Physics
American Geophysical Union
Scholarly Commons Citation
Luo, H., Kronberg, E. A., Nykyri, K., Trattner, K. J., Daly, P. W., Chen, G. X., Du, A. M., & Ge, Y. S. (2017). IMF Dependence of Energetic Oxygen and Hydrogen Ion Distributions in the Near-Earth Magnetosphere. Journal of Geophysical Research: Space Physics, 122(5). https://doi.org/10.1002/2016JA023471