Findings Validate Radial Model of Galactic Center Cosmic Ray Propagation


NEWS from The Starburst Foundation

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February 2000

New Findings Validate Radial Model of
Galactic Center Cosmic Ray Propagation


Support theory that intense cosmic ray outbursts from
the Galactic center periodically bombard the Earth


Radio telescope observations of Sagittarius A*, the luminous radio source at the center of the Milky Way, confirm a cosmic ray theory proposed in 1983 by Dr. Paul LaViolette. Speaking on January 13th at the 195th meeting of the American Astronomical Society, Dr. G. Bower, and his coworkers H. Falcke and D. Backer, reported finding that the synchrotron radio emission from Sagittarius A* was primarily circularly polarized, rather than linearly polarized like most other sources.

Synchrotron radiation is a broadband radio wave emission that is produced when cosmic ray electrons spiral around magnetic field lines perpendicular to the field line direction. If these magnetic field lines are oriented transverse to our line of sight, the electron orbits will be seen edge-on and their synchrotron radio emission will be seen as linearly polarized. On the other hand, if these field lines point towards us so that we look down their field axis, the orbiting electrons would now be observed circling in the plane of the sky, and their radio emission would be seen by us as being circularly polarized.

Dr. Bower did not offer an explanation for the reported polarization finding, calling it “mysterious.” However, during the question period, Dr. LaViolette pointed out that circular polarization would be produced if this synchrotron radiation were emitted by cosmic ray electrons that were traveling radially outward from the Galactic core.

Previously, astronomers had assumed that cosmic ray electrons radiating out from the core would be trapped by nearby magnetic field lines oriented cross-wise to the particles’ outward trajectories, thereby impeding their escape. LaViolette’s model predicted that these fields are instead oriented primarily parallel to the particle flight trajectories and radial with respect to the Galactic core. He maintained that these electrons escape from the core at close to the speed of light, spiraling outward along radial trajectories. Due to their high speed flight, these particles would beam their synchrotron radiation forward, confined to a very narrow angle cone. Consequently, if LaViolette’s theory of radial cosmic ray flight is correct, we should only see radiation coming to us from cosmic ray particles that are traveling almost directly towards us and shining their radio emission cones in our direction. Since we would be sighting down their flight axis, at a low pitch angle to that axis, we would have a face-on view of their orbital trajectories about this flight axis and be seeing their beamed radiation as circularly polarized.

Dr. LaViolette noted that these newly announced results support the “Galactic superwave” model he had proposed in 1983. This postulates that intense cosmic rays emitted from the Galactic core during its explosive activity phase travel radially outward at relativistic speeds and penetrate tens of thousands of light years through the Galactic disk to ultimately bombard our solar system. His proposal of long-range radial propagation was validated several years later by observations that our planet is being showered by pulses of cosmic rays emitted from X-ray pulsars Cygnus X-3 and Hercules X-1. LaViolette’s theory predicted that galactic core cosmic rays radiate out from the centers of other galaxies in a similar fashion.

Others present at the session, such as astrophysicist Dr. Roger Blandford, concurred with LaViolette’s interpretation that the observed circular polarization was evidence of low pitch angle synchrotron radiation emitted from electrons following radial trajectories.