Recovery of 150250 MeV/nuc Cosmic Ray Helium Nuclei Intensities Between 20042010 Near the Earth, at Voyager 2 and Voyager 1 in the Heliosheath  A Two Zone Helioshpere
Abstract
The recovery of cosmic ray He nuclei of energy ~150250 MeV/nuc in solar cycle #23 from 2004 to 2010 has been followed at the Earth using IMP and ACE data and at V2 between 7492 AU and also at V1 beyond the heliospheric termination shock (91113 AU). The correlation coefficient between the intensities at the Earth and at V1 during this time period is remarkable (0.921), after allowing for a ~0.9 year delay due to the solar wind propagation time from the Earth to the outer heliosphere. To describe the intensity changes and to predict the absolute intensities measured at all three locations we have used a simple spherically symmetric (no drift) twozone heliospheric transport model with specific values for the diffusion coefficient in both the inner and outer zones. The diffusion coefficient in the outer zone, assumed to be the heliosheath from about 90 to 120 (130) AU, is determined to be ~5 times smaller than that in the inner zone out to 90 AU. This means the Heliosheath acts much like a diffusing barrier in this model. The absolute magnitude of the intensities and the intensity changes at V1 and the Earth are described to within a few percent by a diffusion coefficient that varies with time by a factor ~4 in the inner zone and only a factor of ~1.5 in the outer zone over the time period from 20042010. For V2 the observed intensities follow a curve that is as much as 25% higher than the calculated intensities at the V2 radius and at times the observed V2 intensities are equal to those at V1. At least onehalf of the difference between the calculated and observed intensities between V1 and V2 can be explained if the heliosphere is squashed by ~10% in distance (nonspherical) so that the HTS location is closer to the Sun in the direction of V2 compared to V1.
 Publication:

arXiv eprints
 Pub Date:
 September 2011
 DOI:
 10.48550/arXiv.1109.1810
 arXiv:
 arXiv:1109.1810
 Bibcode:
 2011arXiv1109.1810W
 Keywords:

 Physics  Geophysics;
 Physics  Space Physics
 EPrint:
 13 Pages, 8 Figures