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Inverse energy dispersion of energetic ions observed in the magnetosheath

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journal contribution
posted on 15.11.2016, 16:01 by S. H. Lee, D. G. Sibeck, K. J. Hwang, Y. Wang, M. V. D. Silveira, M. C. Fok, B. H. Mauk, I. J. Cohen, J. M. Ruohoniemi, N. Kitamura, J. L. Burch, B. L. Giles, R. B. Torbert, C. T. Russell, M. Lester
We present a case study of energetic ions observed by the Energetic Particle Detector (EPD) on the Magnetospheric Multiscale spacecraft in the magnetosheath just outside the subsolar magnetopause that occurred at 1000Â UT on 8 December 2015. As the magnetopause receded inward, the EPD observed a burst of energetic (∼50–1000Â keV) proton, helium, and oxygen ions that exhibited an inverse dispersion, with the lowest energy ions appearing first. The prolonged interval of fast antisunward flow observed in the magnetosheath and transient increases in the H components of global ground magnetograms demonstrate that the burst appeared at a time when the magnetosphere was rapidly compressed. We attribute the inverse energy dispersion to the leakage along reconnected magnetic field lines of betatron-accelerated energetic ions in the magnetosheath, and a burst of reconnection has an extent of about 1.5Â RE using combined Super Dual Auroral Radar Network radar and EPD observations.

Funding

We thank the FGM, FPI, and EPD instrument teams of MMS mission and ARTEMIS mission for the successful spacecraft operation and for providing plasma and magnetic field data. This research was supported by an appointment to the NASA Postdoctoral Program appointment at the NASA/GSFC, administered by Universities Space Research Association through a contract with NASA. Some of the work conducted at NASA/GSFC was supported by the MMS project. J.M.R. acknowledges the support of NSF under AGS-1341918. M.L. is supported by NERC grant NE/K011766/1. The SuperDARN radars are funded by the national scientific agencies of Australia, Canada, China, France, Japan, South Africa, United Kingdom, and the United States. We thank the team of Katie Herlingshaw, Suzie Imber, Hammed Lawal, Tim Yeoman, Jasmine Sandhu, Rosie Johnson, and Timothy David at the University of Leicester who collected the Hankasalmi radar data used in this paper which supported the CAPER rocket campaign. We thank the national institutes that support them and INTERMAGNET for promoting high standards of magnetic observatory practice. We also thank E. Yizengaw, E. Zesta, M.B. Moldwin, and the rest of the AMBER team for the data. AMBER is operated by Boston College and funded by NASA and AFOSR.

History

Citation

Geophysical Research Letters, 2016, 43 (14), pp. 7338-7347

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Geophysical Research Letters

Publisher

American Geophysical Union (AGU), Wiley

issn

0094-8276

eissn

1944-8007

Acceptance date

02/07/2016

Available date

15/11/2016

Publisher version

http://onlinelibrary.wiley.com/doi/10.1002/2016GL069840/abstract

Notes

The Kp and Dst indices were provided by the website (http://wdc.kugi.kyoto-u.ac.jp/).

Language

en