Voyagers 1 and 2 in a shrunken and squashed heliosphere
Abstract
We have extended our earlier calculations of the distance to the heliospheric termination shock (HTS), which covered the period from the launch of V1 and V2 in 1977 to 2005, to the period from 2006 to 2011. During this latter period, the solar wind speed, ram pressure, and magnetic field decreased to the lowest levels in recent history, related to the sunspot minimum in 20082009. The HTS distance has decreased correspondingly so that V1, which was crossed by the HTS at 94 AU in late 2004, would now, in early 2011, be expected to reach the HTS at a distance of ∼80 AU, when the HTS distance would be expected to be at its minimum. Similarly, V2, which was crossed by the HTS at 84 AU in mid2007, would, in early 2011, reach the HTS at a distance of only 74 AU. These distances, in early 2011, are ∼15% less than those at which V1 and V2 initially reached the HTS. The distance to the heliopause (HP) is more uncertain, but recent calculations place its equilibrium distance at between 1.4 and 1.6 times the HTS distance. Allowing for an additional 1 year for the HP to reach its equilibrium minimum distance relative to the HTS would mean that, assuming this distance remains a constant fraction larger than the HTS distance, the HP distance would be at its minimum distance of (1.41.6) × 80 AU = 112128 AU at V1 in early 2012. At this time, V1 will be in the direction of a distance of ∼120 AU so that there is a possibility that V1 could cross the HP and enter interstellar space at the time 2012.0 ± 1 year. If the crossing does not happen during this time period, then it is unlikely that V1 will reach this defining boundary before about 2016 because of the expected outward motion of the HTS and the HP toward their more normal distances of 8596 and ∼120140 AU, coincident with the maximum of the new sunspot cycle.
 Publication:

Journal of Geophysical Research (Space Physics)
 Pub Date:
 June 2011
 DOI:
 10.1029/2011JA016478
 arXiv:
 arXiv:1101.3533
 Bibcode:
 2011JGRA..116.6105W
 Keywords:

 Interplanetary Physics: Heliopause and solar wind termination;
 Interplanetary Physics: Heliosphere/interstellar medium interactions;
 Interplanetary Physics: Solar wind plasma;
 Interplanetary Physics: Solar cycle variations (7536);
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 23 pages including 7 figures