Fig. 2 |. MMS observations of energetic ions and context data during and after the encounter with the HFA.

b–d, Heavy-ion (CNOⁿ⁺; b), helium (Heⁿ⁺; c) and proton (H⁺; d) data from the energetic particle detector EIS (EPD/EIS). The colour scales show the differential fluxes and the energies shown (on the y axes) are the total energy per incident ion. e, Pitch angle distributions for 70–105-keV ions from the EPD/FEEPS instruments. For b–e, the data were compiled from counts on the EIS or FEEPS instruments on all four spacecraft. f, g, Total ion energy distributions from all four FEEPS instruments (f) and the DIS instrument on MMS-3 (g). a, Magnetic-field vector components and strength from MMS-3, for context. The grey, dashed, vertical lines mark the HFA shock and the bow shock, as labelled. The energetic ions were first observed within the HFA around 05:27 ut and then continuously after the HFA through the ion foreshock and into the magnetosheath until around 05:33 ut.