Investigation of solar flare tracks in IDPs: Some recent results

Abstract

Latent solar cosmic ray (SCR) tracks were studied in selected olivine and pyroxene crystals of stratospheric dust particles (IDPs) using a transmission electron microscope operating at 200 ke V voltage. As a reference, terrestrial and meteoritic olivine and pyroxene single crystals were heavy ion irradiated at GSI with doses of 10 9 -10 10 cm -2 of Ar-, Ge-, Zr-, Nb-, and U-ions in the energy range of 3.9 to 18 MeV/amu using additional Al-degrader foils to cover the solar flare energy spectrum. Most of the track containing IDPs show track densities of ∼ 10 10 cm -2 which is consistent with interplanetary exposure ages in the order of ∼ 10 4 years. The highest track density observed so far in an IDP is 5 × 10 11 cm -2 . Direct lattice images of single latent heavy ion tracks at a resolution of better than 18 Å reveal details of their microstructure that are not accessible to indirect measuring techniques like small-angle scattering or etching of samples containing high density uniform tracks.