When Voyager 1 finally crossed the "termination shock" at the edge of interstellar space in December 2004, space physicists anticipated the long-sought discovery of the source of anomalous cosmic rays. These cosmic rays, among the most energetic particle radiation in the solar system, are thought to be produced at the termination shock -- the boundary at the edge of the solar system where the million-mile-per-hour solar wind abruptly slows. A mystery unfolded instead when Voyager data showed 20 years of predictions to be wrong.
This schematic diagram cuts through the termination shock at the equator. Inside the termination shock, the magnetic field line spirals out and connects to the shock. Also shown are the approximate positions of Voyager 1 at the “nose” of the termination shock and Voyager 2 farther back.
A new theory published in the February 17 issue of the Geophysical Research Letters by Dr. David McComas of Southwest Research Institute and Dr. Nathan Schwadron of Boston University explains why the energization of anomalous cosmic rays is almost entirely absent where Voyager passed through the blunt nose of the termination shock. While the shape of the shock was formerly thought to be unimportant, the new theory explains how this shape is the major factor in particle energization.
McComas and Schwadron say that understanding the role of the termination shocks shape in the energization of anomalous cosmic rays may be a stepping stone to understanding the influence of shock shapes for energization of particle radiation throughout the cosmos. Shocks energize many forms of this dangerous particle radiation, which pose significant hazards to astronauts on space missions, such as future manned missions to the Moon and Mars.
Kira Edler | EurekAlert!
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