K. Meziane, A. J. Hull, R. P. Lin, T. J. Freeman, D. E. Larson Space Sciences Laboratory, University of California, Berkeley, CA, USA G. K. Parks, University of Washington, Seattle, WA, USA
We discuss in detail the observation of energetic ions (30 keV - 1 MeV)
measured by the WIND-3DP Plasma and Energetic Particle experiment at
the Earth's bow shock. The events are observed near the electron
foreshock boundary, and it seems that their occurence requires the
presence of a relatively high ion flux of ambient energetic ions as in
CIR or SEP events.
Upstream, the ion energy-spectrum is usually peaked at few hundreds of keV. The ion propagate upstream with an angular distribution peaked at 30 degrees pitch-angle. However, the angular distribution is non-gyrotropic with a range of gyrophase <~ 180 degrees. In the downstream side of the shock, the angular distribution of energetic particles is peaked at ~ 90 degrees and also appears non gyrotropic.
We study the gyrophase range versus the energy and the shock velocity along the upstream field line; we compare the results with particle simulations.
On the other hand, we show that the energy-spectrum is consistent with an adiabatic-like reflection at the shock of the incoming CIR ions. However, the pitch angle distribution is satisfied only within a certain range of gyrophase angle. Similar comparison is made for energetic ions observed downstream.