[FPSPACE] Cosmic Ray Science from Voyager

[LARRY KLAES]

Cosmic Ray Science from Voyager

Are the Voyager spacecraft still doing good science? You bet, as witness the 
passage of Voyager 1 through the termination shock at the edge of 
interstellar space. Scientists had assumed the craft’s crossing of this 
boundary, where the solar wind abruptly slows, would confirm previous 
theories about anomalous, energetic cosmic rays that were thought to be 
produced in the region. But Voyager did anything but, finding the cosmic ray 
count to be far lower than predicted during its passage.

New work by David McComas (Southwest Research Institute) and Nathan 
Schwadron (Boston University), published recently in the Geophysical 
Research Letters, offers a theory why. They base their thinking on the shape 
of the shock itself, previously thought to be circular. The duo showed that 
a more realistic shape made sense. “In fact, the termination shock couldn’t 
be circular because the solar system is moving through the galaxy, which 
would create more of a flattened egg shape,” says Schwadron. “A flattening 
of the nose of the termination shock leads to a time dependant acceleration 
process.”

According to the new model, the nose of the acceleration shock (Voyager 1’s 
approximate location) is not where particles are best accelerated. Rather, 
they can only reach highest energies after moving along the sides, or 
flanks, of the shock, where the magnetic field has had longer connection 
times to accelerate particles.

The rest of the article and a diagram here:

http://www.centauri-dreams.org/?p=559