GALACTIC EXPLOSIONS, COSMIC DUST INVASIONS, AND CLIMATIC CHANGE

The hypothesis (Galactic Explosion Hypothesis, GEH) is put forth that about every 10,000 years or so the center of our Galaxy enters an explosive phase during which it generates an outburst of cosmic rays with total particle energies on the order of 10('57) ergs or more. These outbursts or "superwaves," composed of highly relativistic electrons and positrons, would travel radially outward through the Galaxy at very close to the speed of light ((TURN)0.99999c) with only moderate attenuation by the interstellar medium ((TURN)20% loss of energy for the journey from the GC to the Sun). It is suggested that upon impacting the solar vicinity, the resulting 10('3) fold elevation in the ambient cosmic ray energy density would initiate a sequence of events which could profoundly influence the Earth's climate. For example, dust and gas vaporized from comets orbiting just outside of the Solar System would become transported into the Solar System which in turn would alter the radiation transmitting properties of the interplanetary medium and of the Earth's stratosphere. Upon accretion by the Sun, this nebular material would also alter the Sun's spectrum and could lead to the initiation of intense solar flare activity. It is proposed that, in various combinations, such effects could trigger the initiation and termination of ice ages, cause geomagnetic reversals, and indirectly bring about mass animal extinctions. It is proposed that the most recent major superwave passed through the solar vicinity beginning about 14,200 years ago and lasted about 2000-3000 years with a major peak occurring about 12,450 years ago.; Astronomical and terrestrial evidence are presented to support the Galactic Explosion Hypothesis. Also, the results of a critical Earth-based test of the hypothesis are presented. In particular, it is reported that the polar ice concentrations of iridium and nickel (both good indicators of extraterrestrial material) rose by one to two orders of magnitude close to the end of the Last Ice Age. These test results are consistent with the GEH prediction that cosmic dust deposition rates were significantly higher during the time when the 14,200 BP Superwave would have been passing through the solar vicinity.