Unlike previous work, in the re-organized reaction network an important cross-termination step replaces an often used but less likely one and a new derivation of the rate model has been provided.
In fact, no crossed terminations were observed.
Voyager 1 will cross the termination shock in the region of high-speed solar wind at latitude of ∼34°.
"Have we passed it?" McDonald says, "or are we just in the vicinity?" The directions of the low-energy particles reflect the speed of the solar wind more directly than the rate of high-energy particles, says Len Fisk of the University of Michigan, Ann Arbor, who suspects that Voyager 1 did cross the termination shock.
Voyager 1 crossed this termination shock at ∼94 AU in 2004, while Voyager 2 crossed it in 2007 at a different heliolatitude, about 10 AU closer to the Sun.
The U.S. space probes Voyager 1 and 2 crossed the termination shock at a distance of 94 and 84 AU from the Sun in 2004 and 2007, respectively.
In the summer of 2002, researchers saw evidence that Voyager had crossed the termination shock.
Voyager 1, launched on Sept. 5, 1977, crossed the termination shock in December 2004 and moved into the heliosheath.
But Frank McDonald of the University of Maryland, College Park, and colleagues report, also in Nature, that higher energy particles increased less than they should have if Voyager 1 had crossed the termination shock.
Observations of the Voyager II termination shock crossing have been published in Nature.
Voyager 2 crossed the solar wind termination shock in August of 2007 (see figure below).
