Quelques idées neuves sur une vieille étoile
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1 Quelques idées neuves sur une vieille étoile J.P. Rozelot OCA-GEMINI Av. Copernic GRASSE
2 The Sun is not a «banal star»
3 The Sun is not a «banal star» Solar cycle activity Solar latitudinal rotation Magnetic activity Other stars Solar radial deplacements Place in the solar system Exobiology Solar shape distortions Consequences on other stars
4 Le Soleil Apex 19 km/s. 1,5 km/s 1,7 km/s 230 km/s Conclusion: la Terre ne repasse jamais au même endroit de l espace 1 an après
5 Qu est-ce que le Soleil? Corps fluide en rotation sur lui même et en déplacement dans l espace.
6 Part I: Sun, differential rotation and outer shape Density ρ = r -n and constant rotation ω Milne (1923), Chandrashekar formula (1933): ε = ( ρ m /ρ c ) ω 2 R/g Where ρ m = mean density moyenne, ρ c = core density du cœur, R = radius, g = surface gravity. b a ε = (a-b)/a r = (a-b) Solar case: Problem!
7 Stellar and Sun Rotation Do Observations permit to verify the nice Chandrasekhar formula? Stars Sun VLT - ESO Turret dome (50-cm) Pic du Midi Some balloon flights (SDS)
8 Altair: 2001 (1.7 M ) r = 424 ± 79 microas Observations About theoretical prediction Achernar: 2003 (6 M ) r = 910 ± 50 microas Far from the theory (more oblate) Sun: ε less than
9 Harmoniques Sphériques: 2-D
10 Sun-Stars-Earth analogy Spherical Zonal harmonic (2,0) spatial resolution km Spherical Zonal harmonic (10,6) spatial resolution 200 km The outer shape of a fluid is distorted under the non uniform distribution of mass and velocity rates
11 Complex rotation profile
12 Complex rotation profile The structure of the Subsurfacic layer: The leptocline Lefebvre, Kosovichev et Rozelot, 2006
13 Observations: Scanning Heliometer (Pic du Midi)
14 Slicing process
15 Shift of the inflexion point and Fried Parameter FFTD P Th F = Data 0,1400 0,1200 Shift Décalage du point d'inflexion 0,1000 0,0800 0,0600 0,0400 0,0200 0,0000-0, seeing
16 Solar limb shape distortions R(θ) ρ=cste = R 0 [ 1 + Σ n c n * P n (θ) ] Best fit data c 2 = ± c 4 = Semi-absolute values of the radius (") Measuread Shape Asphericity c 2 and c Observed Best Legendre's Polynomial fit P 2 and P Theoretical He liog raphic latitude Armstrong & Kuhn, 1999: c 2 = ( r) max = 22 mas
17 The activity cycle Was the Sun «bigger»? Evolution Evolution of of the the solar solar radius radius variations variations Above the mean Mean: Below the mean Earth Climatic Effects? Rozelot, JASTP, 2000, After Toulmonde, M.: 1995, Ph. D. Thesis, Paris (and up-graded by J.P. Rozelot) After Toulmonde, M.: 1995, Ph. D. Thesis, Paris (and up-graded by J.P. Rozelot)
18 Complex outer shape Conclusion : (leptocline) Rozelot, Lefebvre & Desnoux, Sol. Phy, 2003.
19 Qu est-ce qui fait que le Soleil est intéressant?
20 La rotation
21 INTERNAL STRUCTURE AND DYNAMICS 3-D Spots Structure (MDI) Velocity measurement of the sound by Doppler effect with MDI Time/distance method km Intensity of the spot = shadow (black) + penumbra (yellow) Higher speed (red) Map of the effects of the solar activity below the surface Lower speed (blue) Kosovichev et al., 2000, Sol. Phys., 192, 159
22 The activity cycle Sunspot numbers provide the longest running record of directly measured solar activity Johannes Hevelius: Schwabe, 1843: solar cycle periodicity 11 ans Modern Maxima Maunder Minimum 1, 2, 3, 4 21, 22, 23...
23 The activity cycle From 1653 De 1653 to à Due to an abnormal N/S rotation? Presence of spots in only one hemisphere? Was the Sun «bigger»? What was the luminosity? Earth Climatic Effects?
24 Solar activity over the last 1150 years: does it correlate with climate? H. Avercamp
25 Solar activity Large ranging time of suppressed solar of activity Ranging time so-called Oort Ranging time so-called Wolf Ranging time so-called Spörer Ranging time so-called Maunder Ranging time so-called Dayton Next large minima is awaited for the years
26 Sunspot number AD Since 1610 telescopic measurement of sunspot number Prior to that, reconstructed sunspot number from C-14, Be-10 Sun is more active since ~1940 than in previous 1100 years Usoskin et al Phys. Rev. Lett.
27 Main problem: how to predict the solar activity? Failure of all «traditional» reconstitution methods FFT, entropy, cyclograms Attempts «neuronal» networks Modelling by MHD Lyaponov exponent: 4 years
28
29
30 Do the same features appear during other solar minima??? Phase anomalies??
31 Helioclimatology The magnetic field!
32 Merci! Side, TR,
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