Conjunction Observations of Energetic Oxygen Ions O + Accumulated in the Sequential Flux Ropes in the High‐Altitude Cusp

Suping Duan , Lei Dai , Chi Wang (1) , Chunlin Cai (2) , Zhaohai He , Yongcun Zhang , H. Rème (3) , I. Dandouras (2)

1 NSSC - National Space Science Center [Beijing]
2 CESR - Centre d'étude spatiale des rayonnements
3 IRAP - Institut de recherche en astrophysique et planétologie

11 Conjunction observations of the electromagnetic field and plasma by Cluster and TC-1 at the 12 dayside magnetosphere are presented to investigate the sequential flux ropes transferred from the 13 low latitude boundary layer (LLBL) to the high altitude cusp on 10 March 2004.Three sequential 14 flux ropes originating from the dayside low latitude magnetopause are first detected by TC-1. 15 After ~ 6 min, three sequential flux ropes accumulated with energetic oxygen ions are also 16 detected by Cluster in the high altitude cusp. The recurrence period of these flux ropes is ~ 3 min. 17 The number density of energetic oxygen ions in the cusp flux rope is ~ 0.25 cm-3 detected from 18 CIS/CODF instrument on Cluster. It is found that oxygen ions with energy lager than 10 keV have 19 a narrow pitch angle (less than 90 degree) distribution in the southern high altitude cusp. While 20 oxygen ions with energy less than 10 keV are distributed in a wide pitch angle from 0 to 180 21 degree. Counter-streaming energetic oxygen ions are found in these flux ropes in the high altitude 22 cusp .This result suggests that the oxygen ions with energy less than 10 keV in the high altitude 23 cusp have two source regions. One is from the dayside magnetopause and the other is from the 24 low altitude cusp. Our investigations provide evidence that flux ropes at dayside low latitude 25 magnetopause can carry energetic oxygen ions into the high altitude cusp region. 26 27 Three key points 28 1) Counter-streaming oxygen ions are observed in the flux ropes in the cusp. 29 2) Energetic oxygen ions accumulated within sequential flux ropes in the high-altitude cusp. 30 3) Conjunction observations present sequential FTEs transfer from the dayside LLBL to the cusp. 31 32

Domaines: Astrophysique [astro-ph]

Suping Duan, Lei Dai, Chi Wang, Chunlin Cai, Zhaohai He, et al.. Conjunction Observations of Energetic Oxygen Ions O + Accumulated in the Sequential Flux Ropes in the High‐Altitude Cusp. Journal of Geophysical Research Space Physics, 2019, 124 (10), pp.7912-7922. ⟨10.1029/2019JA026989⟩. ⟨hal-02408921⟩