1. The fate of O⁺ ions observed in the plasma mantle and cusp: particle tracing modelling and Cluster observations
- Author
-
Schillings, Audrey, Gunell, Herbert, Nilsson, Hans, Spiegeleer, Alexandre, Ebihara, Yusuke, Westerberg, Lars G., Yamauchi, Masatoshi, and Slapak, Rikard
- Subjects
Physics::Plasma Physics ,Physics::Space Physics ,Astrophysics::Earth and Planetary Astrophysics ,Physics::Geophysics - Abstract
Ion escape is of particular interest for studying the evolution of the atmosphere on geological time scales. Previously, using Cluster-CODIF data, we investigated the oxygen ion outflow from the plasma mantle for different solar wind conditions and geomagnetic activity. We found significant correlations between solar wind parameters, geomagnetic activity (Kp index) and the O+ outflow. From these studies, we suggested that O+ ions observed in the plasma mantle and cusp have enough energy and velocity to escape the magnetosphere and be lost into the solar wind or in the distant magnetotail. Thus, this study aims to investigate where do the ions observed in the plasma mantle end up. In order to answer this question, we numerically calculate the trajectories of O+ ions using a tracing code to further test this assumption and determine the fate of the observed ions. Our code consists of a magnetic field model (Tsyganenko T96) and an ionospheric potential model (Weimer 2001) in which particles initiated in the plasma mantle and cusp regions are launched and traced forward in time. We analysed 136 observations of plasma mantle or cusp events in Cluster data between 2001 and 2007, and for each event 200 O+ particles were launched with an initial parallel and perpendicular velocity corresponding to the bulk velocity observed by Cluster. From the observations, our results show that 93 % of the events have an initial parallel velocity component twice the initial perpendicular velocity. After the tracing, we found that 96 % of the particles are lost into the solar wind or in the distant tail. Out of these 96 %, 20 % escape into the dayside magnetosphere.
- Published
- 2020