Cluster observations of unusually high concentration of energetic O+ carried by flux ropes in the nightside high‐latitude magnetosheath during a storm initial phase. Issue 10 (3rd October 2015)

• Record Type: Journal Article
• Authors: Duan, Suping; Dai, Lei; Wang, Chi; Lui, A. T. Y.; Liu, Zhenxing; He, Zhaohai; Zhang, Yongcun; Dandouras, I.; Reme, H.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 10(2015:Oct.)
• Page Start: 8317
• Page End: 8326
• Publication Date: 2015-10-03
• Subjects: energetic O+ ions -- storm -- flux rope -- magnetosheath; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021306
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We present measurements from Cluster spacecraft to investigate the energetic singly charged oxygen ions, O +, within the flux ropes in the nightside high‐latitude magnetosheath during the initial phase of an intense storm on 24 October 2011. Three magnetic flux ropes were identified by Cluster 4 in the intervals from 20:10 UT to 20:20 UT. Unusually, large number density of energetic O + ions at energy of tens of keV was detected within these flux ropes. The number density of O + ions was above 0.1 cm −3 and the maximum value was about 0.25 cm −3, 1 order of magnitude larger than the ambient value (~0.01 cm −3 ) in the magnetosheath. The O + /H + ratio is as large as ~0.08 within the flux ropes. Enhanced convection electric fields Ey (~10 mV/m) are associated with the flux rope and the high concentrations of energetic O + . The flux ropes, which are presumably produced by magnetic reconnection at the dayside magnetopause or cusp, are convected at a larger velocity than the tailward velocity of ambient flows in the magnetosheath. These observations together show that abundant energetic O + ions are carried by the flux ropes toward tail in the nightside magnetosheath. Our observations present new evidence for a chain linking the dayside to the nightside in the global O + transport process. Key Points: Energetic O + observed in the nightside high‐latitude magnetosheath Abundant energetic O + carried by flux ropes toward tail in magnetosheath Number density of O + was above 0.1 cm −3 and up to 0.25 cm −3