Interplay between tidal flows and magnetic fields in nonlinear simulations of stellar and planetary convective envelopes

Abstract

Stars and planets in close systems are magnetised but the influence of magnetic fields on their tidal responses (and vice versa) and dissipation rates has not been well explored. We present exploratory nonlinear magnetohydrodynamical (MHD) simulations of tidally-excited inertial waves in convective envelopes. These waves probably provide the dominant contribution to tidal dissipation in several astrophysical settings, including tidal circularisation of solar-type binary stars and hot Jupiters, and orbital migration of the moons of Jupiter and Saturn. We model convective envelopes as incompressible magnetised fluids in spherical shells harbouring an initially (rotationally-aligned) dipolar magnetic field. We find that depending on its strength (quantified by its Lehnert number Le) and the magnetic Prandtl number Pm, the magnetic field can either deeply modify the tidal response or be substantially altered by tidal flows. Simulations with small Le exhibit strong tidally-generated differential rotation (zonal flows) for sufficiently large tidal amplitudes, such that both the amplitude and topology of the initial magnetic field are tidally impacted. In contrast, strong magnetic fields can inhibit these zonal flows through large-scale magnetic torques, and by Maxwell stresses arising from magneto-rotational instability, which we identify and characterise in our simulations, along with the role of torsional Alfvén waves. Without tidally-driven zonal flows, the resulting tidal dissipation is close to the linear predictions. We quantify the transition Le as a function of Pm, finding it to be comparable to realistic values found in solar-like stars, such that we predict complex interactions between tidal flows and magnetic fields.

25 pages, 22 figures, accepted in MNRAS

References in corpus (45)

• Magnetic fields of non-degenerate stars
• Tidal dissipation in stars and giant planets
• Comparing Jupiter interior structure models to Juno gravity measurements and the role of a dilute core
• Tidal dissipation in rotating giant planets
• Tidal dissipation in rotating solar-type stars
• Simulations of dynamo action in fully convective stars
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• Turbulent geodynamo simulations: a leap towards Earth's core
• Observations of Cool-Star Magnetic Fields
• New type of magneto-rotational instability in cylindrical Taylor-Couette flow
• Tides in rotating barotropic fluid bodies: the contribution of inertial waves and the role of internal structure
• Tidal dissipation in evolving low-mass and solar-type stars with predictions for planetary orbital decay
• Nonlinear evolution of tidally forced inertial waves in rotating fluid bodies
• Reconciling solar and stellar magnetic cycles with nonlinear dynamo simulations
• Effect of the rotation and tidal dissipation history of stars on the evolution of close-in planets
• The variation of tidal dissipation in the convective envelope of low-mass stars along their evolution
• Tidal dissipation in rotating fluid bodies: a simplified model
• Non-axisymmetric Magnetorotational Instabilities in Cylindrical Taylor-Couette Flow
• Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in planets I. From the PMS to the RGB at solar metallicity
• Geomagnetic acceleration and rapid hydromagnetic wave dynamics in advanced numerical simulations of the geodynamo
• Destabilisation of hydrodynamically stable rotation laws by azimuthal magnetic fields
• Tidal dissipation in rotating fluid bodies: the presence of a magnetic field
• Tidally driven dynamos in a rotating sphere
• 3D evolution of magnetic fields in a differentially rotating stellar radiative zone
• The dynamics and excitation of torsional waves in geodynamo simulations
• Tidal dissipation due to inertial waves can explain the circularization periods of solar-type binaries
• Oscillations of rotating magnetised neutron stars with purely toroidal magnetic fields
• On the relation of standard and helical magnetorotational instability
• Magnetic fields driven by tidal mixing in radiative stars
• Magnetic effect on dynamical tide in rapidly rotating astronomical objects
• Dynamical tides in Jupiter and other rotationally flattened planets and stars with stable stratification
• Calculating rotating hydrodynamic and magneto-hydrodynamic waves to understand magnetic effects on dynamical tides
• Interplay between magnetic fields and differential rotation in a stably stratified stellar radiative zone
• Magneto--Coriolis waves in a spherical Couette flow experiment
• Dynamical tides in Jupiter and the role of interior structure
• Mean zonal flows induced by weak mechanical forcings in rotating spheroids
• Magnetohydrodynamic Simulations of the Tayler Instability in Rotating Stellar Interiors
• The effects of nonlinearities on tidal flows in the convective envelopes of rotating stars and planets in exoplanetary systems
• Turbulent viscosity and effective magnetic Prandtl number from simulations of isotropically forced turbulence
• Oscillations of magnetic stars: II. Axisymmetric toroidal and non-axisymmetric shear Alfven modes in a spherical shell
• Tidal dissipation due to the elliptical instability and turbulent viscosity in convection zones in rotating giant planets and stars
• Does magnetic field impact tidal dynamics inside the convective zone of low-mass stars along their evolution?
• A $r$-mode in a magnetic rotating spherical layer: application to neutron stars
• Transport properties of the Azimuthal Magnetorotational Instability
• On obliquely magnetized and differentially rotating stars

Cited by in corpus (5)

• Tidally driven inertial waves enhance eccentricity damping and spin evolution in planets and stars
• Non-linear saturation of gravito-inertial modes excited by tidal resonances in binary neutron stars
• Evolving Low- and Intermediate-Mass Binaries: Departures from Classical Theory
• Observational imprints of tidal internal gravity wave dissipation in star-planet systems
• The stability of propagating plane inertial waves in rotating fluids