From Tides to Currents: Unraveling the Mechanism That Powers WASP-107b's Internal Heat Flux
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| Format: | Preprint |
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2025
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| _version_ | 1866918007284957184 |
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| author | Batygin, Konstantin |
| author_facet | Batygin, Konstantin |
| contents | The sub-Jovian exoplanet WASP-107b ranks among the best-characterized low-density worlds, featuring a Jupiter-like radius and a mass that lies firmly in the sub-Saturn range. Recently obtained JWST spectra reveal significant methane depletion in the atmosphere, indicating that WASP-107b's envelope has both a high metallicity and an elevated internal heat flux. Together with a detected non-zero orbital eccentricity, these data have been interpreted as evidence of tidal heating. However, explaining the observed luminosity with tidal dissipation requires an unusually low tidal quality factor of $Q \sim 100$. Moreover, we find that secular excitation by the RV-detected outer companion WASP-107c, generally cannot sustain WASP-107b's eccentricity in steady state against tidal circularization. As an alternative explanation, we propose that Ohmic dissipation -- generated by interactions between zonal flows and the planetary magnetic field in a partially ionized atmosphere -- maintains the observed thermal state. Under nominal assumptions for the field strength, atmospheric circulation, and ionization chemistry, we show that Ohmic heating readily accounts for WASP-107b's inflated radius and anomalously large internal entropy. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_01581 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | From Tides to Currents: Unraveling the Mechanism That Powers WASP-107b's Internal Heat Flux Batygin, Konstantin Earth and Planetary Astrophysics The sub-Jovian exoplanet WASP-107b ranks among the best-characterized low-density worlds, featuring a Jupiter-like radius and a mass that lies firmly in the sub-Saturn range. Recently obtained JWST spectra reveal significant methane depletion in the atmosphere, indicating that WASP-107b's envelope has both a high metallicity and an elevated internal heat flux. Together with a detected non-zero orbital eccentricity, these data have been interpreted as evidence of tidal heating. However, explaining the observed luminosity with tidal dissipation requires an unusually low tidal quality factor of $Q \sim 100$. Moreover, we find that secular excitation by the RV-detected outer companion WASP-107c, generally cannot sustain WASP-107b's eccentricity in steady state against tidal circularization. As an alternative explanation, we propose that Ohmic dissipation -- generated by interactions between zonal flows and the planetary magnetic field in a partially ionized atmosphere -- maintains the observed thermal state. Under nominal assumptions for the field strength, atmospheric circulation, and ionization chemistry, we show that Ohmic heating readily accounts for WASP-107b's inflated radius and anomalously large internal entropy. |
| title | From Tides to Currents: Unraveling the Mechanism That Powers WASP-107b's Internal Heat Flux |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2505.01581 |