Models of Star-Planet Magnetic Interaction

Strugarek, Antoine

doi:10.1007/978-3-319-30648-3_25-1

Cited by 8 publications

(20 citation statements)

References 69 publications

(96 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We will assume a characteristic size of the planet's magnetosphere based on the pressure equilibrium between the magnetic pressure due to the planetary magnetic field and the ambient pressure in the stellar wind. This approximation gives a satisfying estimate of the magnetospheric size at the front of the interaction in 3D simulations (Strugarek 2016), and generally under-estimate it in the magnetospheric tail. A more realistic estimate of the magnetospheric shape and size in the equatorial plane would not affect the main conclusions of our study.…”

Section: Location Of the Interaction Foot-point On The Stellar Surfacementioning

confidence: 91%

“…The orbit of Kepler-78b is shown by the dashed white circle, and the magnetic field lines connecting the orbit of the planet to the stellar surface are highlighted by the colored field lines. (Saur et al 2013;Strugarek 2016Strugarek , 2017a. We show the inclination angles in the upper panel of Figure 3.…”

Section: Wind Properties Along the Orbitmentioning

confidence: 99%

“…where A 1 = 2.5, C 1 = 0.83, ξ 0 = 0.44, ξ 1 = −0.3 and χ = 0.25 are constants that were fitted with 3D numerical simulations in Strugarek (2016) and Strugarek (2017a), and Θ M is the relative inclination of the planetary field with respect to the ambient magnetic field B w . The drag coefficient is defined as c d = M a / 1 + M 2 a , and we left out any dependencies on the resistive properties of the planet ionosphere and stellar wind for the sake of simplicity (see Strugarek 2016 for more details).…”

Section: Magnetic Power Of the Star-planet Magnetic Interaction Alongmentioning

confidence: 99%

“…Planets on short-period orbit are expected to interact strongly with their host star (Cuntz et al 2000) due to the strong irradiation they receive (Yelle et al 2008;Trammell et al 2014;Matsakos et al 2015;Bourrier et al 2016;Daley-Yates & Stevens 2018), the strong tidal forces they experience (Mathis 2017;Bolmont et al 2017;Strugarek et al 2017b), and the strong interplanetary magnetic field they orbit in (see Lanza 2010;Cohen et al 2011;Strugarek 2016, 2017b, andreferences therein). Such close-in planets will generally orbit in the sub-alfvénic region of the accelerating wind of their star.…”

Section: Introductionmentioning

confidence: 99%

“…Alfvén wings are a very robust feature of SPMIs as they are triggered whether or not the planet's atmosphere escapes, and whether or not the planet posseses a magnetosphere (Neubauer 1998). SPMIs were shown to be able to channel magnetic powers up to 10 19 -10 20 W in the most favorable star-planet systems (Saur et al 2013;Strugarek 2016). These large energy fluxes can in principle leave observable traces in stellar atmospheres, through e.g.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Strugarek

Brun

Donati

et al. 2019

ApJ

View full text Add to dashboard Cite

Observational evidence of star-planet magnetic interactions (SPMI) in compact exo-systems have been looked for in the past decades. Indeed planets in close-in orbit can be magnetically connected to their host star, and channel Alfvén waves carrying large amounts of energy towards the central star. The strength and temporal modulation of SPMIs are primarily set by the magnetic topology of the host star and the orbital characteristics of the planet. As a result, SPMI signals can be modulated over the rotational period of the star, the orbital period of the planet, or a complex combination of the two. The detection of SPMI thus have to rely on multiple-epochs and multiple-wavelengths observational campaigns. We present a new method to characterize SPMIs and apply it to Kepler-78, a late G star with a super-Earth on an 8.5 hours orbit. We model the corona of Kepler-78 using the large-scale magnetic topology of the star observed with Zeeman-Doppler-Imaging. We show that the closeness of Kepler-78b allows the interaction to channel energy flux densities up to a few kW m −2 towards the central star. We show that this flux is large enough to be detectable in classical activity tracers such as Hα. It is nonetheless too weak to explain the modulation observed by Moutou et al. (2016). We furthermore demonstrate how to predict the temporal modulation of SPMI signals in observed systems such as Kepler-78. The methodology presented here thus paves the road towards denser, specific observational campaigns that would allow a proper identification of SPMIs in compact star-planet systems.

show abstract

Section: Location Of the Interaction Foot-point On The Stellar Surfacementioning

confidence: 91%

Section: Wind Properties Along the Orbitmentioning

confidence: 99%

Section: Magnetic Power Of the Star-planet Magnetic Interaction Alongmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Strugarek

Brun

Donati

et al. 2019

ApJ

View full text Add to dashboard Cite

show abstract

Magnetic and tidal migration of close-in planets

Ahuir

Strugarek

Brun

et al. 2021

A&A

View full text Add to dashboard Cite

Context. Over the last two decades, a large population of close-in planets has been detected around a wide variety of host stars. Such exoplanets are likely to undergo planetary migration through magnetic and tidal interactions. Aims. We aim to follow the orbital evolution of a planet along the structural and rotational evolution of its host star, simultaneously taking into account tidal and magnetic torques, in order to explain some properties of the distribution of observed close-in planets. Methods. We rely on a numerical model of a coplanar circular star–planet system called ESPEM, which takes into account stellar structural changes, wind braking, and star–planet interactions. We browse the parameter space of the star–planet system configurations and assess the relative influence of magnetic and tidal torques on its secular evolution. We then synthesize star–planet populations and compare their distribution in orbital and stellar rotation periods to Kepler satellite data. Results. Magnetic and tidal interactions act together on planetary migration and stellar rotation. Furthermore, both interactions can dominate secular evolution depending on the initial configuration of the system and the evolutionary phase considered. Indeed, tidal effects tend to dominate for high stellar and planetary masses as well as low semi-major axis; they also govern the evolution of planets orbiting fast rotators while slower rotators evolve essentially through magnetic interactions. Moreover, three populations of star–planet systems emerge from the combined action of both kinds of interactions. First, systems undergoing negligible migration define an area of influence of star–planet interactions. For sufficiently large planetary magnetic fields, the magnetic torque determines the extension of this region. Next, planets close to fast rotators migrate efficiently during the pre-main sequence, which engenders a depleted region at low rotation and orbital periods. Then, the migration of planets close to slower rotators, which happens during the main sequence, may lead to a break in gyrochronology for high stellar and planetary masses. This also creates a region at high rotation periods and low orbital periods not populated by star–planet systems. We also find that star–planet interactions significantly impact the global distribution in orbital periods by depleting more planets for higher planetary masses and planetary magnetic fields. However, the global distribution in stellar rotation periods is marginally affected, as around 0.5% of G-type stars and 0.1% of K-type stars may spin up because of planetary engulfment. More precisely, star–planet magnetic interactions significantly affect the distribution of super-Earths around stars with a rotation period higher than around 5 days, which improves the agreement between synthetic populations and observations at orbital periods of less than 1 day. Tidal effects for their part shape the distribution of giant planets.

show abstract

Modelling the imposed magnetospheres of Mars-like exoplanets: star–planet interactions and atmospheric losses

Basak

Nandy

2021

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Based on 3D compressible magnetohydrodynamic (MHD) simulations, we explore the interactions between the magnetized wind from a solar-like star and a Mars-like planet – with a gravitionally stratified atmosphere – which is either non-magnetized or hosts a weak intrinsic dipolar field. The primary mechanism for the induction of a magnetosphere around a non-magnetized conducting planet is the pile-up of stellar magnetic fields in the day side region. The magnetopause stand-off distance decreases as the strength of the planetary dipole field is lowered and saturates to a minimum value for the case of a planet with no magnetic field. Global features such as bowshock, magnetosheath, magnetotail and strong current sheets are observed in the imposed magnetosphere. We explore variations in atmospheric mass loss rates for different stellar wind strengths to understand the impact of stellar magnetic activity and plasma winds – and their evolution – on (exo)planetary habitability. In order to simulate a case analogous to the present-day Mars, a planet without atmosphere is considered. The results are found to be in good agreement with observational data from Mars missions such as MGS and MAVEN.

show abstract

Models of Star-Planet Magnetic Interaction

Cited by 8 publications

References 69 publications

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Chasing Star–Planet Magnetic Interactions: The Case of Kepler-78

Magnetic and tidal migration of close-in planets

Modelling the imposed magnetospheres of Mars-like exoplanets: star–planet interactions and atmospheric losses

Contact Info

Product

Resources

About