Shocklets, SLAMS, and field-aligned ion beams in the terrestrial foreshock

L. B. Wilson, A. Koval, D. G. Sibeck, A. Szabo, C. A. Cattell, J. C. Kasper, B. A. Maruca, M. Pulupa, C. S. Salem, M. Wilber

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32 Scopus citations


We present Wind spacecraft observations of ion distributions showing field-aligned beams (FABs) and large-amplitude magnetic fluctuations composed of a series of shocklets and short large-amplitude magnetic structures (SLAMS). The FABs are found to have Tb ∼80 - 850 eV, Vb/V sw ∼1. 3 - 2. 4, T∥,b/Tb ∼1-8, and nb/no ∼0.2-11%. Saturation amplitudes for ion/ion resonant and non-resonant instabilities are too small to explain the observed SLAMS amplitudes. We show two examples where groups of SLAMS can act like a local quasi-perpendicular shock reflecting ions to produce the FABs, a scenario distinct from the more common production at the quasi-perpendicular bow shock. The SLAMS exhibit a foot-like magnetic enhancement with a leading magnetosonic whistler train, consistent with previous observations. Strong ion and electron heating are observed within the series of shocklets and SLAMS with temperatures increasing by factors ≠5 and ≠3, respectively. Both the core and halo electron components show strong perpendicular heating inside the feature. Key Points Field-aligned ion beams produced locally by SLAMS SLAMS cause strong anisotropic ion and electron heating SLAMS can act like local quasi-perpendicular shocks

Original languageEnglish (US)
Pages (from-to)957-966
Number of pages10
JournalJournal of Geophysical Research: Space Physics
Issue number3
StatePublished - 2013


  • field-aligned ion beams
  • particle acceleration
  • particle reflection
  • wave-particle interaction
  • whistler mode waves


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