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Title: On the Magnetic Protection of the Atmosphere of Proxima Centauri b

Abstract

The discovery of exoplanets orbiting red dwarfs, such as Proxima Centauri b, has led to questions of their habitability and capacity to retain liquid surface water. While Proxima b is in a “temperate orbit,” i.e., an Earth at that location would not freeze or boil its oceans, its proximity to a parent star with quite high magnetic activity is likely to influence its atmospheric evolution and habitability. Planetary magnetic fields can prevent direct stripping away of the planetary atmosphere by the stellar wind, but ion escape can still occur at the magnetic poles. This process, the polar wind, is well known to occur at Earth and may have contributed to the habitability of Earth’s early atmosphere. The polar wind is highly variable and sensitive to both ionizing radiation and geomagnetic activity. The higher ionizing radiation levels of M dwarfs at habitable zone distances are expected to increase the polar wind by orders of magnitude and, instead of helping create a habitable atmosphere, may strip away enough volatiles to render the planet inhospitable. Here, we compute the ionospheric outflow of an Earth-twin subject to the enhanced stellar EUV flux of Proxima b, and the effect on atmospheric escape timescales. We showmore » that an Earth-like planet would not survive the escape of its atmosphere at that location, and therefore the pathway to habitability for Proxima b requires a very different atmospheric history than that of Earth.« less

Authors:
;  [1];  [2];  [3]
  1. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
  2. Harvard Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  3. NASA Langley, Hampton, VA (United States)
Publication Date:
OSTI Identifier:
22654429
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 844; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAPACITY; EVOLUTION; IONIZING RADIATIONS; MAGNETIC FIELDS; MASS; ORBITS; PLANETARY ATMOSPHERES; PLANETS; SATELLITE ATMOSPHERES; SATELLITES; STARS; STELLAR WINDS; STRIPPING

Citation Formats

Garcia-Sage, K., Glocer, A., Drake, J. J., Gronoff, G., and Cohen, O., E-mail: katherine.garcia-sage@nasa.gov. On the Magnetic Protection of the Atmosphere of Proxima Centauri b. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA7ECA.
Garcia-Sage, K., Glocer, A., Drake, J. J., Gronoff, G., & Cohen, O., E-mail: katherine.garcia-sage@nasa.gov. On the Magnetic Protection of the Atmosphere of Proxima Centauri b. United States. doi:10.3847/2041-8213/AA7ECA.
Garcia-Sage, K., Glocer, A., Drake, J. J., Gronoff, G., and Cohen, O., E-mail: katherine.garcia-sage@nasa.gov. Thu . "On the Magnetic Protection of the Atmosphere of Proxima Centauri b". United States. doi:10.3847/2041-8213/AA7ECA.
@article{osti_22654429,
title = {On the Magnetic Protection of the Atmosphere of Proxima Centauri b},
author = {Garcia-Sage, K. and Glocer, A. and Drake, J. J. and Gronoff, G. and Cohen, O., E-mail: katherine.garcia-sage@nasa.gov},
abstractNote = {The discovery of exoplanets orbiting red dwarfs, such as Proxima Centauri b, has led to questions of their habitability and capacity to retain liquid surface water. While Proxima b is in a “temperate orbit,” i.e., an Earth at that location would not freeze or boil its oceans, its proximity to a parent star with quite high magnetic activity is likely to influence its atmospheric evolution and habitability. Planetary magnetic fields can prevent direct stripping away of the planetary atmosphere by the stellar wind, but ion escape can still occur at the magnetic poles. This process, the polar wind, is well known to occur at Earth and may have contributed to the habitability of Earth’s early atmosphere. The polar wind is highly variable and sensitive to both ionizing radiation and geomagnetic activity. The higher ionizing radiation levels of M dwarfs at habitable zone distances are expected to increase the polar wind by orders of magnitude and, instead of helping create a habitable atmosphere, may strip away enough volatiles to render the planet inhospitable. Here, we compute the ionospheric outflow of an Earth-twin subject to the enhanced stellar EUV flux of Proxima b, and the effect on atmospheric escape timescales. We show that an Earth-like planet would not survive the escape of its atmosphere at that location, and therefore the pathway to habitability for Proxima b requires a very different atmospheric history than that of Earth.},
doi = {10.3847/2041-8213/AA7ECA},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 844,
place = {United States},
year = {2017},
month = {7}
}