The May 2‐3, 1986 magnetic storm: First energetic ion composition observations with the Mics instrument on Viking

Measurements with the Magnetospheric Ion Composition Spectrometer (MICS) onboard the polar orbiting Swedish satellite VIKING clearly show a strong asymmetry between the dusk‐ and dawnside ion distributions obtained after the onset of a magnetic storm on May 2‐3, 1986. The eveningside of the inner ring current region is quickly filled by protons with energies of some tens of keV. The morningside continues for several hours to show the quiet‐time inner ring current proton spectra in which protons below ∼100 keV have been removed due to charge‐exchange processes. The data obtained at high latitudes will be compared with measurements of the CHEM instrument on the AMPTE/CCE spacecraft near the equatorial plane. The observations are discussed in context of the convection of injected ions into the inner magnetosphere during magnetically active periods.