Cosmic origin 26Al and cosmic ray intensity in the far past

Application of the 26Al cosmogenic isotope to investigation of long-period variations in cosmic rays in the past has been considered. 26Al is produced in extraterrestrial objects (meteorites, the surface of the Moon, interplanetary dust) and on the Earth (in the upper layers of the atmosphere and on the planet surface). As a result of ablation in the atmosphere meteorites lose all the information on the solar radiation. Therefore lunar soil and interplanetary dust samples are under investigation. Theoretical calculations and experimental measurements of the 26Al activities may be conformed to the depth of approximately 8 cm only, which imposes certain restrictions on studying the long-period variations of cosmic rays in the past. It is supposed that cosmogenic 26Al is produced in the interplanetary dust under the action of solar protons. In the upper layers of the atmosphere 26Al is produced by cosmic rays on 40Ar. The density of the cosmic dust particles with extra-atmospheric 26Al has the lower limit 2.9 gxcm-3, whereas the atmospheric one precipitating on aerosols into the ocean is below 2.9 gxcm-3. Thus it is possible to investigate separately terrestrial and extraterristrial fractions containing 26Al. A scheme of βγγ coincidences has been proposed in order to obtain more comprehensive depth distribution of the 26Al activity in bottom sedimentation