PROBING THE SOLAR SURFACE: THE OBLATENESS AND ASTROPHYSICAL CONSEQUENCES
| Autor: | C. Damiani, Jean-Pierre Rozelot, S. Pireaux |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Physics
Astronomy Astronomy and Astrophysics Solar radius Astrophysics Gravitational energy Stars Theory of relativity Space and Planetary Science Physics::Space Physics Moment (physics) Astrophysics::Solar and Stellar Astrophysics Solar rotation Astrophysics::Earth and Planetary Astrophysics Helioseismology Variation (astronomy) |
| Zdroj: | The Astrophysical Journal. 703:1791-1796 |
| ISSN: | 1538-4357 0004-637X |
| DOI: | 10.1088/0004-637x/703/2/1791 |
| Popis: | Based on historical records, the Sun's dimensions are temporally dependent. Until the recent past, varying dimensions were keenly disputed. Recent accurate observations have removed the doubt, whether from direct limb observations or from helioseismology f-modes analysis. A shrinking or an expanding shape is ultimately linked to solar activity, as even a small variation in the solar radius causes variations in gravitational energy. Based on accurate space- and ground-based observations, we will argue that the oblateness of the Sun is time dependent. Indeed, considering the first two shape coefficients, we can interpret such a temporal variation as a change in the relative importance of the hexadecapolar term, i.e., at the time of high activity, only the dipolar moment c 2 has a significant effect, but at the time of low activity, c 4 is predominant; this results in a decrease of the total value of the oblateness. The combination of the two terms leads to a solar oblateness varying along with solar activity. More studies are needed to get accurate measurements from space, which will provide us with the unique opportunity to study detailed changes of global solar properties. |
| Databáze: | OpenAIRE |
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