Voyager Observations of Galactic Ions and Electrons in the Heliosheath

Abstract

Voyager observations of galactic cosmic ray ions and electrons in the heliosheath now extend from 2004.96 to 2009.2, covering a significant part of the cycle 23 recovery from near solar maximum to solar minimum conditions. While the radial intensity gradient of 265 MeV/n GCR He in mid-2008 was 0.1 ± 0.2 %/AU, its rate of intensity increase since mid-2006 has been 7.4 %/year. The rate of increase for lower rigidity GCRs (200 MeV/n He, 260 MeV H) is even higher. 10 MeV electrons are increasing at a rate of 60% a year over the same period, strongly supporting a galactic origin for this component. For GCR ions the increase appears to be mainly temporal while for electrons the increase is both temporal and spatial. This continuing increase in cosmic ray intensity may be in part related to the reduced magnetic field strength observed in the inner heliosphere. A comparison of the changes of the GCR ions and electrons suggest that the galactic component may not enter near the nose of the heliosphere but at the flanks or in the tail region.

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