Unusual Enhancements of MeV Ions and Electrons as Voyager 1 Approaches the Heliospheric Termination Shock

Abstract

In mid-2002 as Voyager 1 moved beyond 85 AU there began an unusual increase of 2.5 MeV ions that remained at a level near 0.1 protons/cm^2-s-sr-MeV for some 6 months. Simultaneously there was an increase in the 2.5 - 70 MeV electrons and in the galactic and anomalous cosmic ray intensity. The electrons are most probably of galactic origin and like the cosmic ray ions are responding to the more favorable modulation levels in the distant heliosphere. It is proposed that the MeV ions are of solar/interplanetary (S/IP) origin with possibly a significant component of IP accelerated pickup ions that have been reaccelerated. Several possibilities for this reacceleration are discussed including the proximity of the termination shock (T.S.).

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