The Effects of Magnetic Fields on Observational Signatures of Atmospheric Escape in Exoplanets: Double Tail Structures

Abstract

Using 3D radiative MHD simulations and Lyman-$\alpha$ transit calculations, we investigate the effect of magnetic fields on the observational signatures of atmospheric escape in exoplanets. Using the same stellar wind, we vary the planet's dipole field strength ($B_p$) from 0 to 10G. For $B_p<3$G, the structure of the escaping atmosphere begins to break away from a comet-like tail following the planet ($B_p=0$), as we see more absorbing material above and below the orbital plane. For $B_p\ge 3$G, we find a ``dead-zone'' around the equator, where low velocity material is trapped in the closed magnetic field lines. The dead-zone separates two polar outflows where absorbing material escapes along open field lines, leading to a double tail structure, above and below the orbital plane. We demonstrate that atmospheric escape in magnetised planets occurs through polar outflows, as opposed to the predominantly night-side escape in non-magnetised models. We find a small increase in escape rate with $B_p$, though this should not affect the timescale of atmospheric loss. As the size of the dead-zone increases with $B_p$, so does the line centre absorption in Lyman-$\alpha$, as more low-velocity neutral hydrogen covers the stellar disc during transit. For $B_p<3$G the absorption in the blue wing decreases, as the escaping atmosphere is less funnelled along the line of sight by the stellar wind. In the red wing (and for $B_p>3$G in the blue wing) the absorption increases caused by the growing volume of the magnetosphere. Finally we show that transits below and above the mid-disc differ caused by the asymmetry of the double tail structure.

Accepted for publication in MNRAS. 12 pages, 8 figures

References in corpus (30)

• Atmospheric Escape from Hot Jupiters
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Stellar magnetism: empirical trends with age and rotation
• Lyman-$\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• Energetic neutral atoms as the explanation for the high velocity hydrogen around HD 209458b
• Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows
• Magnetically controlled mass loss from extrasolar planets in close orbits
• Magnetic field strengths of hot Jupiters from signals of star-planet interactions
• Hubble Space Telescope detection of oxygen in the atmosphere of exoplanet HD189733b
• Atmosphere Expansion and Mass Loss of Close-Orbit Giant Exoplanets heated by Stellar XUV. II. Effects of Planetary Magnetic Field, Structuring of inner Magnetosphere
• Stellar Winds on the Main-Sequence I: Wind Model
• Magnetohydrodynamic Simulations of Hot Jupiter Upper Atmospheres
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• Global 3D hydrodynamic modeling of in-transit Lyα absorption of GJ436b
• Into the Storm: Diving into the winds of the ultra hot Jupiter WASP-76 b with HARPS and ESPRESSO
• FUV variability of HD 189733. Is the star accreting material from its hot Jupiter?
• Two regimes of interaction of a Hot Jupiter's escaping atmosphere with the stellar wind and generation of energized atomic hydrogen corona
• Near-ultraviolet Transmission Spectroscopy of HD 209458b: Evidence of Ionized Iron Beyond the Planetary Roche Lobe
• Effects of the stellar wind on the Ly-alpha transit of close-in planets
• The dichotomy of atmospheric escape in AU Mic b
• MOVES II. Tuning in to the radio environment of HD189733b
• GJ 436b and the stellar wind interaction: simulations constraints using Ly$\alpha$ and H$\alpha$ transits
• Hydrodynamical interaction of stellar and planetary winds: effects of charge exchange and radiation pressure on the observed Ly$\alpha$ absorption
• Influence of the Sun-like magnetic cycle on exoplanetary atmospheric escape
• Lambda And: A post-main sequence wind from a solar-mass star
• The circumstellar environment of 55 Cnc: The super-Earth 55 Cnc e as a primary target for star-planet interactions

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• Large-scale structures in the stellar wind of fast-rotating stars spawned by the presence of Earth-like planets
• Atmospheric mass loss and stellar wind effects in young and old systems II: Is TOI-942 the past of TOI-421 system?
• Atmospheric mass loss and stellar wind effects in young and old systems I: comparative 3D study of TOI-942 and TOI-421 systems