On the Origin of High-Energy Particles in the Cusp Diamagnetic Cavity

K. Nykyri, A. Otto, E. Adamson, E. Kronberg, P. Daly

Research output: Contribution to journalArticlepeer-review

Abstract

We have analyzed Cluster magnetic field and plasma data during a high-altitude cusp crossing in 2003. The Cluster separation was ∼5000 km and provided unique measurements of high energy particle properties both inside the DiaMagnetic Cavity (DMC) and surrounding magnetosheath. Most of the high energy electrons and protons had pitch angles of ∼90° in the cavity and the high energy particle intensities dropped as a function of distance from the cavity boundary. By assuming conservation of the first adiabatic invariant for the electrons our analysis indicates that most of the high-energy electrons in the diamagnetic cavity cannot directly originate from the magnetosheath or from the magnetosphere. Our test particle simulations in a local 3-D high-resolution MHD cusp model show that particles can gain up to 40 keV and their pitch angles become nearly 90° in the local cusp geometry due to gradients in reconnection ‘quasi-potential’ agreeing with the Cluster RAPID observations. These results strongly support a local acceleration of particles in the cusp diamagnetic cavities.
Original languageAmerican English
JournalJournal of Atmospheric and Solar-Terrestrial Physics
Volume87/88
DOIs
StatePublished - Oct 2012

Keywords

  • cusp
  • particle acceleration
  • MHD and test particle modeling
  • Cluster spacecraft observations

Disciplines

  • Astrophysics and Astronomy

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