The spiral structure of the Milky Way, cosmic rays, and ice age epochs on Earth

By N. Shaviv. 2002

189 citations recorded by the source corpus.

Abstract The short term variability of the galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This picture has been recently shown to be supported by various data [PhRvL 89 (2002) 051102]. In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance ice ages. Here, we expand upon the original treatment with a more thorough analysis and more supporting evidence. In particular, we discuss the cosmic ray diffusion model which considers the motion of the galactic spiral arms. We also elaborate on the structure and dynamics of the Milky Way’s spiral arms. In particular, we bring forth new argumentation using HI observations which imply that the galactic spiral arm pattern speed appears to be that which fits the glaciation period and the cosmic-ray flux record extracted from Iron meteorites. In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period of 1 to 2 Gyr before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/de9223daf8412de70f98dca4f239aa1ccd1be457

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In Astronomy and Astrophysics

Citations in the corpus

Cosmoclimatology: a new theory emerges (2007, background): “However, revised solar models suggest a nearabsence of cosmic rays (Shaviv 2003b, Svensmark 2003).”
The Spiral Arms and Interarm Separation of the Milky Way: An Updated Statistical Study (2005, background): “Shaviv (2003) found a correlation between the ice age epochs and the change in Galactic cosmic-ray flux as a function of the Sun’s orbit around the Milky Way, as a result of its passage in and out of successive spiral arms.”
Celestial driver of Phanerozoic climate (2003, methodology): “While the number that fits the geological and meteoritic data is supported by a strong theoretical argument ( Shaviv, 2002b ), the meaning of the second number is not yet resolved.”
Global Catastrophic Risks (2008, background): “Thus, Shaviv (2002) has proposed that when the solar system passes through the Galactic spiral arms, the heliosphere is exposed to a much higher cosmic ray flux, which increases the average low-altitude cloud cover and reduces the average global temperature.”