Solar flare tracks in Rio Negro (L 4) chondrite

Abstract

The Rio Negro meteorite contains a small fraction of olivine and pyroxene grains which have extremely high track density (6x 10⁶ - 2.5x 10⁷ tracks/cm^-2). a factor of 10 to 100 higher than the track density observed in a large number of grains taken from close by locations. The low track density (10⁴ - lO⁶cm^-2) is attributed to galactic cosmic ray irradiation of the meteorite during its exposure in the interplanetary space. The high track density (6x 10⁶-2.5x lO⁷cm^-2) is attributed to the irradiation of individual grains to solar flare VH & VVH nuclei hefore compaction of the meteorite body. The results are discussed in terms of irradiation environment of the track rich grains.