Energy flux determines magnetic field strength of planets and stars
| Autor: | Ulrich R. Christensen, Volkmar Holzwarth, Ansgar Reiners |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Physics
Multidisciplinary 010504 meteorology & atmospheric sciences Field (physics) Brown dwarf Astronomy Field strength Astrophysics 01 natural sciences Exoplanet Jupiter Stars Planet 0103 physical sciences Dynamo theory Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics 0105 earth and related environmental sciences |
| Zdroj: | Nature. 457(7226) |
| ISSN: | 1476-4687 |
| Popis: | The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable. |
| Databáze: | OpenAIRE |
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