Interstellar propagation and electron capture processes of galactic cosmic ray heavy ions in space

Abstract

The new information on galactic cosmic rays (GCR) derived from the Spacelab-3 cosmic ray experiment “Anuradha” shows that at 25–125 MeV/N GCR sub-iron and iron (Z = 21–28) particles consists of a mixture of partially ionized and fully ionized ions. Computation of electron capture and loss cross sections in hydrogen in 1–50 MeV/N energy range are made for Fe, Cr, Ti and Ni. From these it is concluded that: (1) these GCR particles must have captured orbital electrons at energies of about 1–5 MeV/N and (2) these particles are then reaccelerated to 300–500 MeV/N most probably in interstellar medium by collisions with SNR shock fronts. Some reacceleration may take place also in heliospheric boundary region. It is suggested that these observations of partially ionized GCR ions of about 100 MeV/N in Spacelab-3 provide a direct evidence of reacceleration of GCR.