2017ApJ...846...47P -
Astrophys. J., 846, 47-47 (2017/September-1)
Ohmic dissipation in mini-Neptunes.
PU B. and VALENCIA D.
Abstract (from CDS):
In the presence of a magnetic field and weakly ionizing winds, ohmic dissipation is expected to take place in the envelopes of Jovian and lower-mass planets alike. While the process has been investigated on the former, there have been no studies done on mini-Neptunes so far. From structure and thermal evolution models, we determine that the required energy deposition for halting the contraction of mini-Neptunes increases with planetary mass and envelope fraction. Scaled to the insolation power, the ohmic heating needed is small: ∼10–5 orders of magnitude lower than for exo-Jupiters ∼10–2. Conversely, from solving the magnetic induction equation, we find that ohmic energy is dissipated more readily for lower-mass planets and those with larger envelope fractions. Combining these two trends, we find that ohmic dissipation in hot mini-Neptunes is strong enough to inflate their radii (∼1015 W for Teq=1400 K). The implication is that the radii of hot mini-Neptunes may be attributed in part to ohmic heating. Thus, there is a trade-off between ohmic dissipation and H/He content for hot mini-Neptunes, adding a new degeneracy for the interpretation of the composition of such planets. In addition, ohmic dissipation would make mini-Neptunes more vulnerable to atmospheric evaporation.
Abstract Copyright:
© 2017. The American Astronomical Society. All rights reserved.
Journal keyword(s):
planets and satellites: composition - planets and satellites: interiors - planets and satellites: physical evolution - planets and satellites: physical evolution
Simbad objects:
3
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