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Journal ArticleDOI

Mass loss of “Hot Jupiters”—Implications for CoRoT discoveries. Part I: The importance of magnetospheric protection of a planet against ion loss caused by coronal mass ejections

01 Apr 2007-Planetary and Space Science (Pergamon)-Vol. 55, Iss: 5, pp 631-642

AbstractAtmospheric erosion due to CME-caused ion pick-up is investigated here for the first time for short periodic gas giants (so-called “Hot Jupiters”) orbiting close to a star. To study the effect of encountering CMEs produced on the magnetospheres and atmospheres of “Hot Jupiters” we model possible interaction of dense CME plasma with the exoplanet HD209458b ( r pl = 1.43 r Jup , M pl = 0.69 M Jup ), which orbits a 4.0–5.0 Gyr old Sun-like star at a distance of about 0.045 AU. A numerical hydrodynamic model is applied for calculation of the upper atmospheric density and the hydrogen wind of HD209458b as a function of planetocentric distance. Taking into account the similarity of HD209458b's host star to our Sun we use for the study of the ion production and loss rate of H + ions the solar CME plasma parameters and apply a numerical test particle model. Tidal-locking of short periodic exoplanets closely located to their host stars should result in weaker intrinsic planetary magnetic moments, as compared to those of the fast rotating Jupiter type planets at much larger orbits. It is shown that in this case the encountering CME plasma can compress the magnetospheric stand-off distance of short periodic “Hot Jupiters” down to the heights at which the ionization and pick-up of the planetary neutral atmosphere by the CME plasma flow take place. Assuming for the host star of HD209458b the same CME occurrence rate as on the Sun, we estimate possible total mass loss rates of HD209458b due to its collisions with CMEs over the planet lifetime. It has been found that under different estimations of the value of a planetary magnetic moment, HD209458b could have lost over its lifetime the mass from 0.2 up to several times of its present mass M pl .

Topics: Hot Jupiter (61%), Exoplanet (60%), Planet (56%), Gas giant (55%), Jupiter (53%)

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Journal ArticleDOI
Abstract: This work reviews factors which are important for the evolution of habitable Earth-like planets such as the effects of the host star dependent radiation and particle fluxes on the evolution of atmospheres and initial water inventories. We discuss the geodynamical and geophysical environments which are necessary for planets where plate tectonics remain active over geological time scales and for planets which evolve to one-plate planets. The discoveries of methane–ethane surface lakes on Saturn’s large moon Titan, subsurface water oceans or reservoirs inside the moons of Solar System gas giants such as Europa, Ganymede, Titan and Enceladus and more than 335 exoplanets, indicate that the classical definition of the habitable zone concept neglects more exotic habitats and may fail to be adequate for stars which are different from our Sun. A classification of four habitat types is proposed. Class I habitats represent bodies on which stellar and geophysical conditions allow Earth-analog planets to evolve so that complex multi-cellular life forms may originate. Class II habitats includes bodies on which life may evolve but due to stellar and geophysical conditions that are different from the class I habitats, the planets rather evolve toward Venus- or Mars-type worlds where complex life-forms may not develop. Class III habitats are planetary bodies where subsurface water oceans exist which interact directly with a silicate-rich core, while class IV habitats have liquid water layers between two ice layers, or liquids above ice. Furthermore, we discuss from the present viewpoint how life may have originated on early Earth, the possibilities that life may evolve on such Earth-like bodies and how future space missions may discover manifestations of extraterrestrial life.

338 citations


Journal ArticleDOI
Abstract: Evidence suggestinganobservable magnetic interaction betweenastar and itshot Jupiter appears asacyclic varia- tion of stellar activity synchronized to the planet's orbit. In this study we monitored the chromospheric activity using several stellar activity indicators of seven stars with hot Jupiters using new high-resolution echelle spectra collected withESPaDOnSoverafewnightsin2005and2006fromtheCFHT(CaiiHk3968,Kk3933,theCaiiinfraredtriplet (IRT)k8662 line, Hk6563, and He i k5876). Synchronicity of the Ca ii H and K emission of HD 179949 with its planet's orbit is clearly seen in four out of six epochs, while rotational modulation with Prot ¼ 7 days is apparent in theothertwoseasons.WeobserveasimilarphenomenononAnd.Thison/off natureof star-planetinteraction(SPI)in the two systems is likely a function of the changing stellar magnetic field structure throughout its activity cycle. Var- iabilityinthetransitingsystemHD 189733islikelyassociatedwithanactiveregionrotatingwiththestar; however,the flaring in excess of the rotational modulation may be associated with its hot Jupiter. As for HD 179949, the peak variability as measured by the mean absolute deviation (MAD) for both HD 189733 andBoo leads the subplanetary longitudeby � 70 � .Thetentativecorrelationbetweenthisactivityandtheratioof Mp sin itotheplanet'srotationperiod, aquantityproportionaltothehotJupiter'smagneticmoment,firstpresentedbyShkolnikandcoworkersremainsviable. Thisworkfurthersthecharacterizationof SPI,improvingitspotentialasaprobeofextrasolarplanetarymagneticfields. Subject headingg planetary systems — radiation mechanisms: nonthermal — stars: activity — stars: chromospheres — stars: individual (� Boo, HD 179949, HD 209458, HD 189733, HD 217107, HD 149143) — stars: late-type

282 citations


Cites background from "Mass loss of “Hot Jupiters”—Implica..."

  • ...…the fact that both hot and very hot Jupiters, such as HD 209458 b and OGLE-TR-56 b, are detected at all means that they must have strong enough magnetic fields to balance the extreme stellar irradiation and CME plasma pressure to prevent destructive atmospheric erosion (Khodachenko et al. 2007)....

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Journal ArticleDOI
TL;DR: It is shown that Earth-like exoplanets within close-in HZs should experience a continuous CME exposure over long periods of time, which may result in little or no magnetospheric protection of planetary atmospheres from a dense flow of CME plasma.
Abstract: Low mass M- and K-type stars are much more numerous in the solar neighborhood than solar-like G-type stars. Therefore, some of them may appear as interesting candidates for the target star lists of terrestrial exoplanet (i.e., planets with mass, radius, and internal parameters identical to Earth) search programs like Darwin (ESA) or the Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The higher level of stellar activity of low mass M stars, as compared to solar-like G stars, as well as the closer orbital distances of their habitable zones (HZs), means that terrestrial-type exoplanets within HZs of these stars are more influenced by stellar activity than one would expect for a planet in an HZ of a solar-like star. Here we examine the influences of stellar coronal mass ejection (CME) activity on planetary environments and the role CMEs may play in the definition of habitability criterion for the terrestrial type exoplanets near M stars. We pay attention to the fact that exoplanets within HZs that ...

275 citations


Journal ArticleDOI
Abstract: The Sun’s magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun. The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment. The emphasis is on the phenomenology related to the production of high-energy photons and particles. Apart from the activity on the young Sun, systematic trends applicable to the entire main-sequence life of a solar analog are discussed.

211 citations


Journal ArticleDOI
Abstract: Aims. We study the possible atmospheric mass loss from 57 known transiting exoplanets around F, G, K, and M-type stars over evolutionary timescales. For stellar wind induced mass loss studies, we estimate the position of the pressure balance boundary between Coronal Mass Ejection (CME) and stellar wind ram pressures and the planetary ionosphere pressure for non- or weakly magnetized gas giants at close orbits. Methods. The thermal mass loss of atomic hydrogen is calculated by a mass loss equation where we consider a realistic heating efficiency, a radius-scaling law and a mass loss enhancement factor due to stellar tidal forces. The model takes into account the temporal evolution of the stellar EUV flux by applying power laws for F, G, K, and M-type stars. The planetary ionopause obstacle, which is an important factor for ion pick-up escape from non- or weakly magnetized gas giants is estimated by applying empirical power-laws. Results. By assuming a realistic heating efficiency of about 10–25% we found that WASP-12b may have lost about 6–12% of its mass during its lifetime. A few transiting low density gas giants at similar orbital location, like WASP-13b, WASP-15b, CoRoT-1b or CoRoT-5b may have lost up to 1–4% of their initial mass. All other transiting exoplanets in our sample experience negligible thermal loss (≤1%) during their lifetime. We found that the ionospheric pressure can balance the impinging dense stellar wind and average CME plasma flows at distances which are above the visual radius of “Hot Jupiters”, resulting in mass losses <2% over evolutionary timescales. The ram pressure of fast CMEs cannot be balanced by the ionospheric plasma pressure for orbital distances between 0.02–0.1 AU. Therefore, collisions of fast CMEs with hot gas giants should result in large atmospheric losses which may influence the mass evolution of gas giants with masses

189 citations


Cites background from "Mass loss of “Hot Jupiters”—Implica..."

  • ...This new steady state will be characterized by higher atmospheric pressures and closer locations of the planetary obstacle together this may result in high non-thermal mass loss rates (Khodachenko et al. 2007)....

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  • ...Thus, from the study of Khodachenko et al. (2007), we know that ion pick-up loss is negligible for “Hot Jupiters” if a planetary obstacle builds up at total atmospheric pressures≤10−4 dyn cm−2 (shadowed area in Fig....

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  • ...Khodachenko et al. (2007) studied the expected minimum and maximum possible atmospheric H+ pick-up erosion of the “Hot Jupiter” HD209458b due to stellar Coronal Mass Ejections (CMEs) and concluded that hydrogen-rich gas giants, which orbit solar-like stars at distances 0.05 AU, would have been…...

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  • ...…in weaker intrinsic magnetic moments, as compared to fast rotating Jupiter-class exoplanets at larger orbital distances (Grießmeier et al. 2004), Khodachenko et al. (2007) found that the encountering of dense stellar wind and CME plasma may compress the magnetosphere and force the…...

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  • ...…Erkaev et al. 2007; Hubbard et al. 2007a,b; Lecavelier des Etangs 2007; Muñoz 2007; Koskinen et al. 2007; Penz et al. 2008a,b; Penz & Micela 2008; Davis & Wheatley 2009; Murray-Clay et al. 2009) and non-thermal (Erkaev et al. 2005; Khodachenko et al. 2007) atmospheric mass loss over their lifetime....

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References
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Journal ArticleDOI
Abstract: Rotation periods are reported for 14 main-sequence stars, bringing the total number of such stars with well-determined rotation periods to 41. It is found that the mean level of their Ca n H and K emission (averaged over 15 years) is correlated with rotation period, as expected. However, there is a further dependence of the emission on spectral type. When expressed as the ratio of chromospheric flux to total bolometric flux, the emission is well correlated with the parameter Pohs/Tc, where Pohs is the observed rotation period and tc(B—V) is a theoretically-derived convective overturn time, calculated assuming a mixing length to scale height ratio a ~ 2. This finding is consonant with general predictions of dynamo theory, if the relation between chromospheric emission and dynamo-generated magnetic fields is essentially independent of rotation rate and spectral type for the stars considered. The dependence of mean chromospheric emission on rotation and spectral type is essentially the same for stars above and below the Vaughan-Preston “gap,” thus casting doubt on explanations of the gap in terms of a discontinuity in dynamo characteristics. Subject headings: Ca n emission — convection — stai

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"Mass loss of “Hot Jupiters”—Implica..." refers background in this paper

  • ...179 (for the cycle minimum and maximum, respectively) and the solar logðRHKÞ (Noyes et al., 1984) value is 4:93 (for S 1⁄4 0:171)....

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  • ...Note that the present time Sun has S-values between 0.167 and 0.179 (for the cycle minimum and maximum, respectively) and the solar logðR0HKÞ (Noyes et al., 1984) value is 4:93 (for S ¼ 0:171)....

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Journal ArticleDOI
Abstract: The flow behind an interplanetary shock was analyzed through the use of magnetic field and plasma data from five spacecraft, with emphasis on the magnetic cloud identified by a characteristic variation of the latitude angle of the magnetic field. The size of the cloud was found to be about 0.5 AU in radial extent and greater than 30 deg in azimuthal extent, with its front boundary almost normal to the radial direction. Because the field direction of the magnetic cloud as it moved past the spacecraft was observed to rotate nearly parallel to a plane, it is thought that the field configuration of the cloud was essentially two-dimensional. These results further suggest that the lines of force in the magnetic cloud formed loops, but it could not be determined whether these loops were open or closed.

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Journal ArticleDOI
13 Mar 2003-Nature
TL;DR: The detection of atomic hydrogen absorption in the stellar Lyman α line during three transits of HD209458b is reported, showing that this absorption should take place beyond the Roche limit and therefore can be understood in terms of escaping hydrogen atoms.
Abstract: The planet in the system HD209458 is the first one for which repeated transits across the stellar disk have been observed1,2. Together with radial velocity measurements3, this has led to a determination of the planet's radius and mass, confirming it to be a gas giant. But despite numerous searches for an atmospheric signature4,5,6, only the dense lower atmosphere of HD209458b has been observed, through the detection of neutral sodium absorption7. Here we report the detection of atomic hydrogen absorption in the stellar Lyman α line during three transits of HD209458b. An absorption of 15 ± 4% (1σ) is observed. Comparison with models shows that this absorption should take place beyond the Roche limit and therefore can be understood in terms of escaping hydrogen atoms.

1,146 citations


"Mass loss of “Hot Jupiters”—Implica..." refers background or methods in this paper

  • ...As was mentioned above, there is an evidence from HST observations (Vidal-Madjar et al., 2003, 2004) and theoretical considerations (Lammer et al., 2003a; Yelle, 2004; Tian et al., 2005; Langmayr et al., 2006) that upper atmospheres of ‘‘Hot Jupiters’’ experience hydrodynamic blow-off....

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  • ...Vidal-Madjar et al. (2003, 2004) inferred from their Lyman-a absorption observations on HD209458b with the space telescope imaging spectrograph (STIS) on board of the hubble space telescope (HST) at about 2:5rpl a reference H number density of about X106 cm 3....

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  • ...As an example we study the interaction of the CME plasma with the well observed short periodic gas giant HD209458b, which orbits a 4.0–5.0Gyr old Sun-like G-type star at 0.045AU (e.g., Barman et al., 2002; Vidal-Madjar et al., 2003)....

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  • ...ARTICLE IN PRESS M.L. Khodachenko et al. / Planetary and Space Science 55 (2007) 631–642632 Vidal-Madjar et al. (2003) observed with the Hubble Space Telescope Imaging Spectrograph (HSTIS) an evaporating hydrogen-rich atmosphere corresponding to a mass loss rate 41010 g s 1 around the short…...

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  • ...However, Vidal-Madjar et al. (2003, 2004) noted that due to saturation effects in the Lyman-a absorption line of their observations, densities which are several orders of magnitude higher would produce similar absorption signatures....

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Journal ArticleDOI
Abstract: [1] The Solar and Heliospheric Observatory (SOHO) mission's white light coronagraphs have observed nearly 7000 coronal mass ejections (CMEs) between 1996 and 2002. We have documented the measured properties of all these CMEs in an online catalog. We describe this catalog and present a summary of the statistical properties of the CMEs. The primary measurements made on each CME are the apparent central position angle, the angular width in the sky plane, and the height (heliocentric distance) as a function of time. The height-time measurements are then fitted to first- and second-order polynomials to derive the average apparent speed and acceleration of the CMEs. The statistical properties of CMEs are (1) the average width of normal CMEs (20° 900 km s−1) show deceleration. Solar cycle variation and statistical properties of CMEs are revealed with greater clarity in this study as compared with previous studies. Implications of our findings for CME models are discussed.

1,000 citations


"Mass loss of “Hot Jupiters”—Implica..." refers background in this paper

  • ...Annual average DCME of non-halo CMEs ranges from 45 (solar minimum) to 61 (close before activity maximum) (Gopalswamy, 2004; Yashiro et al., 2004)....

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