Planet Mercury was located about 43° west of the Earth-Sun line at ̃ 0.46 AU distance from the Sun on 20-22 April 1998. A proton flare appeared at the Sun on 20 April (W 90° , S 47° , 9:38-11:19 UT) and Mercury was hit by energetic protons and α -particles which released probably pickup and sputter ions from the planetary surface. The WIND/SC, located in the libration point L1 in April 1998, was connected via the interplanetary magnetic field with Mercury. The SMS-experiment detected in the energy/charge ranges 0.5-9.5 and 6.5- 225 keV/e singly charged heavy ions above the solar cosmic ray background which we interprete partly as Mercury ions. However a contribution of pickup ions from the dust located near the Sun cannot be excluded.
26th International Cosmic Ray Conference (ICRC26), Volume 6
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