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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 34, issue 2
Ann. Geophys., 34, 249–257, 2016
https://doi.org/10.5194/angeo-34-249-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 34, 249–257, 2016
https://doi.org/10.5194/angeo-34-249-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 17 Feb 2016

Regular paper | 17 Feb 2016

Energetic ions scattered into the loss cone with observations of the Cluster satellite

Ying Xiong1,2, Zhigang Yuan1, and Jingfang Wang1 Ying Xiong et al.
  • 1School of Electronic Information, Wuhan University, Wuhan, China
  • 2School of Computer Science, Hubei University of Technology, Wuhan, China

Abstract. In this paper, we report in situ observations by the Cluster spacecraft of energetic ions scattered into the loss cone during the inbound pass from the plasma sheet into the plasmasphere. During the inbound pass of the plasma sheet, Cluster observed the isotropy ratio of energetic ions to gradually decrease from unity and the isotropic boundary extended to lower L value for higher-energy ions, implying that the field line curvature scattering mechanism is responsible for the scattered ions into the loss cone from the plasma sheet. In the outer boundary of a plasmasphere plume, Cluster 3 observed the increase of the isotropy ratio of energetic ions accompanied by enhancements of Pc2 waves with frequencies between the He+ ion gyrofrequency and O+ ion gyrofrequency estimated in the equatorial plane. Those Pc2 waves were left-hand circularly polarized and identified as electromagnetic ion cyclotron (EMIC) waves. Using the observed parameters, the calculations of the pitch angle diffusion coefficients for ring current protons demonstrate that EMIC waves could be responsible for the ions scattering and loss-cone filling. Our observations provide in situ evidence of energetic ion loss in the plasma sheet and the plasmasphere plume. Our results suggest that energetic ions scattering into the loss cone in the central plasma sheet and the outer boundary of the plasmaspheric plume are attributed to the field line curvature scattering mechanism and EMIC wave scattering mechanism, respectively.

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With observations of the Cluster spacecraft, we report in situ evidence of energetic ions scattered into the loss cone during the inbound pass from the plasma sheet into the plasmasphere. Our results suggest that energetic ions scattering into the loss cone in the central plasma sheet and the outer boundary of the plasmaspheric plume are attributed to the field line curvature scattering mechanism and EMIC wave scattering mechanism, respectively.
With observations of the Cluster spacecraft, we report in situ evidence of energetic ions...
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