An Earth-like Stellar Wind Environment For Proxima Centauri c

Simulated stellar wind environment for the Proxima Cen system. Multi-domain models for activity minimum (left) and maximum (right) are shown. The top panels contain the dynamo-generated surface field distributions (in G) used to drive the AWSoM solution within the innermost module (SC, middle panels). This domain contains the orbits of Proxima b (white solid) and the tentative innermost planet Proxima d (white dashed). The purple iso-surface corresponds to the Alfv´en surface of the stellar wind (MA = 1, see text for details). The steady-state solution is propagated from the coupling region (105 − 110 RF) to the entire IH domain (4500 RF in each cartesian direction; bottom panels). This domain contains the orbit of Proxima c (yellow). Magenta and green iso-surfaces delimitate the slow (Ur . 750 km/s) and fast (Ur & 1500 km/s) wind sectors, respectively. Color-coded is the wind dynamic pressure (Pdyn = ρ U2 ) normalized to the nominal Sun-Earth value (∼ 1.5 nPa), visualized on the equatorial plane of both domains. Selected magnetic field lines are shown in white.

A new planet has been recently discovered around Proxima Centauri. With an orbital separation of ∼1.44 au and a minimum mass of about 7 M⊕, Proxima c is a prime direct imaging target for atmospheric characterization.

The latter can only be performed with a good understanding of the space environment of the planet, as multiple processes can have profound effects on the atmospheric structure and evolution. Here, we take one step in this direction by generating physically-realistic numerical simulations of Proxima's stellar wind, coupled to a magnetosphere and ionosphere model around Proxima c. We evaluate their expected variation due to the magnetic cycle of the host star, as well as for plausible inclination angles for the exoplanet orbit.

Our results indicate stellar wind dynamic pressures comparable to present-day Earth, with a slight increase (by a factor of 2) during high activity periods of the star. A relatively weak interplanetary magnetic field at the distance of Proxima c leads to negligible stellar wind Joule heating of the upper atmosphere (about 10% of the solar wind contribution on Earth) for an Earth-like planetary magnetic field (0.3 G). Finally, we provide an assessment of the likely extreme conditions experienced by the exoplanet candidate Proxima d, tentatively located at 0.029 au with a minimum mass of 0.29 M⊕.

Julián D. Alvarado-Gómez (1), Jeremy J. Drake (2), Cecilia Garraffo (3 and 2), Ofer Cohen (4), Katja Poppenhäger (1 and 5), Rakesh K. Yadav (3), Sofia P. Moschou (2) ((1) Leibniz Institute for Astrophysics Potsdam, (2) Center for Astrophysics | Harvard & Smithsonian, (3) Harvard University, (4) University of Massachusetts Lowell, (5) University of Potsdam)

Comments: 9 Pages, 4 Figures, 1 Table. Accepted for publication in The Astrophysical Journal Letters (ApJL)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2009.07266 [astro-ph.SR] (or arXiv:2009.07266v1 [astro-ph.SR] for this version)

Submission history
From: Julián David Alvarado-Gómez Dr. rer. nat.
[v1] Tue, 15 Sep 2020 17:57:35 UTC (5,268 KB)

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