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38 Manuel Güdel Flux density at 1 AU (erg s −1 cm −2 Å −1 ) 50 45 40 35 30 25 20 15 10 5 0 0.1 Gyr (EK Dra) 0.3 Gyr (π 1 UMa + χ 1 Ori) 0.65 Gyr (κ 1 Cet) Fe XXIII Fe XIX Fe XVIII Fe XXII Fe XV He II Fe XVI 100 150 200 250 300 350 Wavelength (Å) Figure 15: Extracts of the EUV spectra of solar analogs with different ages. All spectral fluxes have been transformed to irradiances at 1 AU from the star. The spectra have been shifted along the ordinate, by multiples of 10 erg cm −2 s −1 ˚A −1 (from Ribas et al., 2005, reproduced by permission of AAS). • Both Figure 16 and 17 show a more prominent continuum in more active stars. Continuum is predominantly formed by bremsstrahlung and is therefore a sensitive temperature indicator. From full spectral interpretation, a tight correlation has indeed been found between the characteristic coronal temperature and the normalized coronal luminosity LX/Lbol: Stars at higher activity levels support hotter coronae (Vaiana, 1983; Schrijver et al., 1984; Stern et al., 1986; Schmitt et al., 1990; Dempsey et al., 1993; Maggio et al., 1994; Gagne et al., 1995a; Schmitt et al., 1995; Hünsch et al., 1996; Güdel et al., 1997b; Preibisch, 1997; Schmitt, 1997; Singh et al., 1999). Figure 18 shows the correlation between average (emission-measure weighted) coronal temperature and the total X-ray luminosity for solar analogs, including solar maximum and minimum values (the latter from Peres et al., 2000). Numerically, the correlation for the stellar sample reads LX = 1.61 × 10 26 T 4.05±0.25 av [erg s −1 ] , (15) where Tav is in MK, and LX has been determined in the 0.1 – 10 keV band (Telleschi et al. 2005, and similar results in Güdel et al. 1997b for the ROSAT energy band). Such relations continue to hold into the PMS domain where exceedingly hot coronae with temperatures up to ≈ 100 MK are found (Imanishi et al., 2001). The trend seen in coronal X-ray emission is similar to the trends described previously for the UV, FUV, and X-ray bands (Sections 5.3, 5.4, and 5.5.1): The emission from stars at higher activity levels is harder, implying that harder emission decays more rapidly in the course of stellar evolution. Three classes of models have been proposed to explain this correlation: • As stellar activity increases, the corona becomes progressively more dominated by hotter and denser features, for example active regions as opposed to quiet areas or coronal holes. Living Reviews in Solar Physics http://www.livingreviews.org/lrsp-2007-3
The Sun in Time: Activity and Environment 39 flux at 1 AU (erg cm -2 s -1 per bin) 4 2 0 30 20 10 0 10 5 0 6 4 2 0 1.0 0.5 0 1.0 0.5 0 0.5 0 0.2 0.1 0 Si XIII Heα Mg XII Lyα Mg XI Heα Ne X Lyβ Ne X Lyα Ne IX Heα Fe XVII Fe XVIII Fe XVII O VIII Lyα O VII Heα BP Tau (bin = 0.05 A) V410 Tau (bin = 0.05 A) 47 Cas (bin = 0.05 A) EK Dra (bin = 0.05 A) π 1 UMa (bin = 0.05 A) χ 1 Ori (bin = 0.05 A) κ 1 Cet (bin = 0.05 A) β Com (bin = 0.0875 A) 10 15 20 25 30 35 wavelength (A) Figure 16: Fluxed high-resolution X-ray spectra of solar analogs with different ages, obtained with the RGS instruments on board XMM-Newton. The topmost two spectra are from K-type T Tauri stars (BP Tau is a classical T Tauri star, V410 Tau a weak-line T Tauri star), while the other spectra are from MS solar analogs. Fluxes are given at a distance of 1 AU from the star, in erg cm −2 s −1 per bin, where the bin width is given in parentheses after the star’s name in each panel (usually 0.05 ˚A except for β Com where a bin width of 0.0875 ˚A has been used). Note the anomalously strong O vii (and also Ne ix) lines in the CTTS BP Tau, indicating an excessive amount of cool plasma (the “soft excess”; adapted from Telleschi et al. 2005 and Telleschi et al. 2007b). N VII Lyα Living Reviews in Solar Physics http://www.livingreviews.org/lrsp-2007-3 C VI Lyα
Page 1 and 2: Living Rev. Solar Phys., 4, (2007),
Page 3 and 4: Contents 1 Introduction 7 2 What is
Page 5: List of Tables 1 Symbols and units
Page 8 and 9: 8 Manuel Güdel The discovery of ex
Page 10 and 11: 10 Manuel Güdel 2 What is a Solar-
Page 12 and 13: 12 Manuel Güdel 3 The Sun in Time
Page 14 and 15: 14 Manuel Güdel Guinan, 1994a; Dor
Page 16 and 17: 16 Manuel Güdel 4 The Solar Magnet
Page 18 and 19: 18 Manuel Güdel 4.1.2 Polar spots
Page 20 and 21: 20 Manuel Güdel structure”; furt
Page 22 and 23: 22 Manuel Güdel Because the X-ray
Page 24 and 25: 24 Manuel Güdel Flux density at bo
Page 26 and 27: 26 Manuel Güdel Figure 7: Left (a)
Page 28 and 29: 28 Manuel Güdel detection until re
Page 30 and 31: 30 Manuel Güdel stellar winds and
Page 32 and 33: 32 Manuel Güdel Figure 11: Relatio
Page 34 and 35: 34 Manuel Güdel 5.4 The far-ultrav
Page 36 and 37: 36 Manuel Güdel X-ray luminosity (
Page 40 and 41: 40 Manuel Güdel count rate (cts s
Page 42 and 43: 42 Manuel Güdel Consequently, the
Page 44 and 45: 44 Manuel Güdel Table 4: Integrate
Page 46 and 47: Relative flux (Sun=1) 46 Manuel Gü
Page 48 and 49: 48 Manuel Güdel Flux at 1 AU (erg
Page 50 and 51: 50 Manuel Güdel Figure 22: Correla
Page 52 and 53: 52 Manuel Güdel a concept also pro
Page 54 and 55: 54 Manuel Güdel • This latter co
Page 56 and 57: 56 Manuel Güdel entire observed X-
Page 58 and 59: 58 Manuel Güdel 5.9.2 The composit
Page 60 and 61: 60 Manuel Güdel Abundance 1.0 0.1
Page 62 and 63: 62 Manuel Güdel 6.2.2 New features
Page 64 and 65: 64 Manuel Güdel Figure 30: Summary
Page 66 and 67: 66 Manuel Güdel among the stars co
Page 68 and 69: 68 Manuel Güdel et al. (2005), and
Page 70 and 71: 70 Manuel Güdel same time, related
Page 72 and 73: 72 Manuel Güdel active stars, incl
Page 74 and 75: 74 Manuel Güdel magnetized; such w
Page 76 and 77: 76 Manuel Güdel low viscous heatin
Page 78 and 79: 78 Manuel Güdel all isotopic anoma
Page 80 and 81: 80 Manuel Güdel 7 The Solar System
Page 82 and 83: 82 Manuel Güdel of life, and life
Page 84 and 85: 84 Manuel Güdel 7.1.3 Cosmic rays
Page 86 and 87: 86 Manuel Güdel H2O + hν → OH +
Page 88 and 89:
88 Manuel Güdel Here, v0 = (2kTexo
Page 90 and 91:
90 Manuel Güdel Figure 41: Modeled
Page 92 and 93:
92 Manuel Güdel Figure 42: Modeled
Page 94 and 95:
94 Manuel Güdel (Section 5.6), one
Page 96 and 97:
96 Manuel Güdel 8 Summary and Conc
Page 98 and 99:
98 Manuel Güdel Solar magnetic act
Page 100 and 101:
100 Manuel Güdel References Acuña
Page 102 and 103:
102 Manuel Güdel Balbus, S.A., Haw
Page 104 and 105:
104 Manuel Güdel Calvet, N., Muzer
Page 106 and 107:
106 Manuel Güdel Curiel, S., Rodr
Page 108 and 109:
108 Manuel Güdel Favata, F., Micel
Page 110 and 111:
110 Manuel Güdel Gagne, M., Cailla
Page 112 and 113:
112 Manuel Güdel Güdel, M., 1997,
Page 114 and 115:
114 Manuel Güdel workshop held at
Page 116 and 117:
116 Manuel Güdel Holman, G.D., Ben
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118 Manuel Güdel Johns-Krull, C.M.
Page 120 and 121:
120 Manuel Güdel König, B., Guent
Page 122 and 123:
122 Manuel Güdel Maggio, A., Peres
Page 124 and 125:
124 Manuel Güdel Mitra-Kraev, U.,
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126 Manuel Güdel Parnell, C.E., Ju
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128 Manuel Güdel Proceedings for a
Page 130 and 131:
130 Manuel Güdel Schmitt, J.H.M.M.
Page 132 and 133:
132 Manuel Güdel Smith, K., Pestal
Page 134 and 135:
134 Manuel Güdel Telleschi, A., G
Page 136 and 137:
136 Manuel Güdel Weber, E.J., Davi
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