MHD study of extreme space weather conditions for exoplanets with
Earth-like magnetospheres: On habitability conditions and radio-emission
Abstract
The present study aims at characterizing the habitability conditions of
exoplanets with an Earth-like magnetosphere inside the habitable zone of
M and F stars, caused by the direct deposition of the stellar wind on
the exoplanet surface. Also, the radio emission generated by exoplanets
with a Earth-like magnetosphere is calculated for different space
weather conditions. The study is based on a set of MHD simulations
performed by the code PLUTO. Exoplanets hosted by M stars at $0.2$ au
are protected from the stellar wind during regular and CME-like space
weather conditions if the star rotation period is slower than $3$
days. Exoplanets hosted by a F stars at $\geq 2.5$ au
are protected during regular space weather conditions, but a stronger
magnetic field compared to the Earth is mandatory if the exoplanet is
close to the inner edge of the star habitable zone ($2.5$ au) during
CMEs. The range of radio emission values calculated in the simulations
are consistent with the scaling proposed by
\citeA{Zarka8} during regular and common CME-like space
weather conditions. If the radio telescopes measure a relative low radio
emission signal with small variability from an exoplanet, that may
indicate favorable exoplanet habitability conditions. The radio emission
power calculated for exoplanets with an Earth-like magnetosphere is in
the range of $3 \cdot 10^{7}$ to $2
\cdot 10^{10}$ W for SW dynamic pressures between
$1.5$ to $100$ nPa and IMF intensities between $50$ - $250$ nT,
and is below the sensitivity threshold of present radio telescopes at
parsec distances.