Magnetic Games Between a Planet and Its Host Star: The Key Role of Topology

Strugarek, Antoine; Brun, Allan Sacha; Matt, Sean P.; Réville, Victor

doi:10.1088/0004-637x/815/2/111

Cited by 102 publications

(140 citation statements)

References 67 publications

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“…However, these percentages fluctuate significantly in time. Such a complex field structure in space and time likely affects the SPMI expected in these close-in systems (Cuntz et al 2000;Ip et al 2004;Strugarek et al 2015).…”

Section: Numerical Resultsmentioning

confidence: 99%

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The Hottest Hot Jupiters May Host Atmospheric Dynamos

Rogers

McElwaine

2017

ApJL

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Hot Jupiters have proven themselves to be a rich class of exoplanets which test our theories of planetary evolution and atmospheric dynamics under extreme conditions. Here, we present three-dimensional magnetohydrodynamic simulations and analytic results which demonstrate that a dynamo can be maintained in the thin, stably-stratified atmosphere of a hot Jupiter, independent of the presumed deep-seated dynamo. This dynamo is maintained by conductivity variations arising from strong asymmetric heating from the planets' host star. The presence of a dynamo significantly increases the surface magnetic field strength and alters the overall planetary magnetic field geometry, possibly affecting star-planet magnetic interactions.

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Section: Numerical Resultsmentioning

confidence: 99%

“…Furthermore, we find that the energy in the dipole component of the magnetic field varies substantially in time. All of these factors affect star-planet magnetic interactions (Strugarek et al 2015) and the inferences we make from such interactions (Vidotto et al 2010). …”

Section: Discussionmentioning

confidence: 96%

The Hottest Hot Jupiters May Host Atmospheric Dynamos

Rogers

McElwaine

2017

ApJL

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“…In this case, the line connecting the star and the planet would not be anchored at the substellar point, but would instead be shifted to a different stellar longitude and/or latitude. Finally, we note that transfers of energy between the star and the planet only occur when the planet is orbiting within the stellar Alfvénic surface (Strugarek et al 2015). Therefore, understanding the realistic distribution of stellar wind particles and magnetic fields are of utmost importance to model and quantify star-planet interactions (Vidotto et al 2014).…”

Section: Understanding the Non-detectionmentioning

confidence: 91%

“…The literature on possible correlations between planetary orbital phase and stellar activity is abundant but inconclusive (e.g., Lanza et al 2011;Lecavelier des Etangs et al 2012;Pillitteri et al 2011Pillitteri et al , 2015. On the other hand, theoretical and numerical models (Lanza 2009;Cohen et al 2011;Matsakos et al 2015;Strugarek et al 2015) have long suggested that magnetic star-planet interaction intermediated by reconnection events could release energetic particles that would travel toward the star, triggering potentially measurable activity enhancement events (but see, e.g., Lanza 2012). Very recently, France et al (2016) found tentative evidence for star-planet interaction from the variation of several FUV lines (NV, CIV, SiIV).…”

Section: Introductionmentioning

confidence: 99%

Is the activity level of HD 80606 influenced by its eccentric planet?

Figueira

Santerne

Mascareño

et al. 2016

A&A

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Aims. Several studies suggest that the activity level of a planet-host star can be influenced by the presence of a close-by orbiting planet. Moreover, the interaction mechanisms that have been proposed, magnetic interaction and tidal interaction, exhibit a very different dependence on the orbital separation between the star and the planet. A detection of activity enhancement and characterization of its dependence on planetary orbital distance can, in principle, allow us to characterize the physical mechanism behind the activity enhancement. Methods. We used the HARPS-N spectrograph to measure the stellar activity level of HD 80606 during the planetary periastron passage and compared the activity measured to that close to apastron. Being characterized by an eccentricity of 0.93 and an orbital period of 111 days, the system's extreme variation in orbital separation makes it a perfect target to test our hypothesis. Results. We find no evidence for a variation in the activity level of the star as a function of planetary orbital distance, as measured by all activity indicators employed: log(R HK ), H α , NaI, and HeI. None of the models employed, whether magnetic interaction or tidal interaction, provides a good description of the data. The photometry revealed no variation either, but it was strongly affected by poor weather conditions. Conclusions. We find no evidence for star-planet interaction in HD 80606 at the moment of the periastron passage of its very eccentric planet. The straightforward explanation for the non-detection is the absence of interaction as a result of a low magnetic field strength on either the planet or the star and of the low level of tidal interaction between the two. However, we cannot exclude two scenarios: i) the interaction can be instantaneous and of magnetic origin, being concentrated on the substellar point and its surrounding area; and ii) the interaction can lead to a delayed activity enhancement. In either scenario, a star-planet interaction would not be detectable with the dataset described in this paper.

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“…These models have used available ZDI maps or low-order idealized magnetic fields to study and scale stellar massloss rates and stellar spindown with stellar age and rotation periods, as well as to characterize the coronae and winds of planet-hosting stellar systems (e.g., Matt et al 2012;Vidotto et al 2014;Matsakos et al 2015;Réville et al 2015;Strugarek et al 2015), while they were not calibrated by solar input parameters and solar magnetogram data. Instead, some of the models have adopted an idealized "fiducial" solar case, which is represented by solar mass, radius, rotation period, and a dipole magnetic field.…”

Section: Introduction the Zeeman-doppler Imagine (Zdi) Techniquementioning

confidence: 99%

A Comparison between Physics-based and Polytropic MHD Models for Stellar Coronae and Stellar Winds of Solar Analogs

Cohen

2017

ApJ

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The development of the Zeeman-Doppler Imagine (ZDI) technique has provided synoptic observations of surface magnetic fields of low-mass stars. This led the Stellar Astrophysics community to adopt modeling techniques that have been used in solar physics using solar magnetograms. However, many of these techniques have been neglected by the solar community due to their failure to reproduce solar observations. Nevertheless, some of these techniques are still used to simulate the coronae and winds of solar analogs. Here we present a comparative study between two MHD models for the solar corona and solar wind. The first type of model is a polytropic wind model, and the second is the physics-based AWSOM model. We show that while the AWSOM model consistently reproduces many solar observations, the polytropic model fails to reproduce many of these observations and in the cases it does, its solutions are unphysical. Our recommendation is that polytropic models, which are used to estimate mass-loss rates and other parameters of solar analogs, must be first calibrated with solar observations. Alternatively, these models can be calibrated with models that capture more detailed physics of the solar corona (such as the AWSOM model), and that can reproduce solar observations in a consistent manner. Without such a calibration, the results of the polytropic models cannot be validated, but they can be wrongly used by others.

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Magnetic Games Between a Planet and Its Host Star: The Key Role of Topology

Cited by 102 publications

References 67 publications

The Hottest Hot Jupiters May Host Atmospheric Dynamos

The Hottest Hot Jupiters May Host Atmospheric Dynamos

Is the activity level of HD 80606 influenced by its eccentric planet?

A Comparison between Physics-based and Polytropic MHD Models for Stellar Coronae and Stellar Winds of Solar Analogs

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