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

Shaviv, Nir J.

doi:10.1016/s1384-1076(02)00193-8

Cited by 191 publications

(228 citation statements)

References 99 publications

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“…Second, the time of passage through the arms is predicted to be from the start of Zone 1 to the end of Zone 3, which is 5/6r 175.96=146.6 Myr. Although this agrees with the periodicity of Fe-Ni meteorite exposure ages (143¡10, Shaviv (2003)) and the 140 Myr signal from the fossil record (Rohde & Muller 2005), it is not clear how the 140 Myr signal would emerge from the arm model presented here. Third, the galactic plane oscillation may be related to the timing through the arms, with an oscillation generated between equal density points in the arms.…”

Section: Resultssupporting

confidence: 53%

“…These previous studies have identified a variety of periods including 26-35 Myr (mantle plumes/ flood basalt events/large igneous provinces (LIPs) and marine genera), 60-62 Myr (marine genera, sea level and LIPs), 135-145 Myr (marine genera, oxygen isotope record as indicator of palaeoclimate, ice age epochs) and even longer periods in different studies of LIPs and mantle plumes (160)(161)(162)(163)(164)(165)(166)(167)(168)(169)(170)330 Myr,. The drivers of these signals are widely debated and include processes intrinsic to Earth and the Solar System (Kemp et al 2005), perturbations of the Oort cloud due to oscillations of the Solar System around its galactic plane (Napier 2006;Stothers 2006 ;Nurmi et al 2001) and interactions with spiral arms and other areas of enhanced star formation during the Sun's galactic orbit (Leitch & Vasisht 1998;Isley & Abbott 2002;Shaviv 2003 ;Marcos & Marcos 2004;Gies & Helsel 2005;Thomas et al 2005;Svensmark 2006).…”

Section: Introductionmentioning

confidence: 99%

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The galactic cycle of extinction

Gillman¹,

Erenler²

2008

International Journal of Astrobiology

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: Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

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Section: Resultssupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

The galactic cycle of extinction

Gillman¹,

Erenler²

2008

International Journal of Astrobiology

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“…the model established by Vallée (2002Vallée ( , 2005, which consists of four logarithmic and symmetrically positioned arms. Around these, we take a Gaussian shape (analogous to the approach in Shaviv 2003) to yield an analytic expression for the source term Q, by summing up over all four arms (n ∈ {1, 2, 3, 4}): with r n = r 0 exp(k(ϕ + ϕ n )), where ϕ n introduces the symmetric rotation of each arm by 90 • , i.e. ϕ n = (n − 1)π/2.…”

Section: Source Distributionmentioning

confidence: 99%

Anisotropic diffusion of Galactic cosmic ray protons and their steady-state azimuthal distribution

Effenberger

Fichtner

Scherer

et al. 2012

A&A

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Galactic transport models for cosmic rays involve the diffusive motion of these particles in the interstellar medium. Owing to the large-scale structured Galactic magnetic field, this diffusion is anisotropic with respect to the local field direction. We included this transport effect along with continuous loss processes in a quantitative model of Galactic propagation for cosmic ray protons that is based on stochastic differential equations. We calculated energy spectra at different positions along the Sun's Galactic orbit and compared them to the isotropic diffusion case. The results show that a larger amplitude of variation and different spectral shapes are obtained in the introduced anisotropic diffusion scenario, which in turn emphasizes the need for accurate Galactic magnetic field models.

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“…How close the Sun is to the corotation circle is still unresolved. Recent studies tend to fall into two camps; most, such as Lépine et al (2001), Dias and Lépine (2005) and Fernandez et al (2001), argue that the Sun is very near the corotation circle, while others (e.g., Martos et al, 2004) argue it is not (see Shaviv 2003 for a summary of this debate). Trimble (1997a,b) considered, in a general way, the metallicity of the Sun in the broader context of Galactic chemical evolution and how the metallicity of the gas in the interstellar medium constrains the formation of habitable planets.…”

Section: The Galactic Habitable Zonementioning

confidence: 99%

Habitable Zones in the Universe

González

2005

Orig Life Evol Biosph

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Abstract. Habitability varies dramatically with location and time in the universe. This was recognized centuries ago, but it was only in the last few decades that astronomers began to systematize the study of habitability. The introduction of the concept of the habitable zone was key to progress in this area. The habitable zone concept was first applied to the space around a star, now called the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable zones have been proposed. We review the historical development of the concept of habitable zones and the present state of the research. We also suggest ways to make progress on each of the habitable zones and to unify them into a single concept encompassing the entire universe.

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

Cited by 191 publications

References 99 publications

The galactic cycle of extinction

The galactic cycle of extinction

Anisotropic diffusion of Galactic cosmic ray protons and their steady-state azimuthal distribution

Habitable Zones in the Universe

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