[8] The characteristic time of proton fluxes decay τ in the events with the exponential decreases was analyzed on the basis of the measurements by the instrument Charged Particle Measurement Experiment (CPME) on the IMP 8 spacecraft during the period from 1974 to 2001. We have used the data for the whole period despite the fact that part of time IMP 8 was within the magnetosphere of the Earth. It looks quite permissible because protons with the energies >1 MeV within the magnetosphere on magnetic shells with L>10 repeat exactly the fluxes of the similar protons outside of the Earth's magnetosphere, and the orbit of the IMP 8 spacecraft never approached the Earth closer than 20 Earth's radii [Paularena and King, 1999]. At such distances the Earth's magnetosphere is not an obstacle even for particles with lower energies.
[9] The channels of registration for protons with the energies 2-4.6, 4.6-15, 15-25, and 25-48 MeV were used. Within the whole period 1974-2001, we detected 642 exponential declines. For each of them the characteristic times of decrease τ for the energies of protons with sufficiently large fluxes were determined. The background is estimated for each channel (this is usually a general instrumental background, determined from the shape at the end of the decay, when observed) and subtracted from the fluxes. The greater part of the decays was related to the events with small particle fluxes. The τ values for them were obtained only for low-energy channels. The amount of events with large particle fluxes that allowed us to investigate high-energy channels (15-48 MeV) comprised 147 events. This gave an opportunity to perform a statistical analysis of different energetic dependences.
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