Atmospheric Mass Loss from High Velocity Giant Impacts. (arXiv:1811.11778v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Yalinewich_A/0/1/0/all/0/1">Almog Yalinewich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schlichting_H/0/1/0/all/0/1">Hilke E. Schlichting</a>
Using moving mesh hydrodynamic simulations, we determine the shock
propagation and resulting ground velocities for a planet hit by a high velocity
impactor. We use our results to determine the atmospheric mass loss caused by
the resulting ground motion due to the impact shock wave. We find that there
are two distinct shock propagation regimes: In the limit in which the impactor
is significantly smaller than the target ($R_i<< R_t$), the solutions are
self-similar and the shock velocity at a fixed point on the target scale as
$m_i^{2/3}$, where $m_i$ is the mass of the impactor, and the ground velocities
follow a universal profile given by
$v_g/v_i=(14.2x^2-25.3x+11.3)/(x^2-2.5x+1.9) +2ln{R_i/R_t}$, where
$x=sinleft(theta/2right)$, $theta$ is the latitude on the target measured
from the impact site, and $v_g$ and $v_i$ are the ground velocity and impact
velocity, respectively. In addition, we find that shock velocities decline with
the mass of the impactor significantly more weakly than $m_i^{2/3}$ in the
limit in which the impactor is comparable to the size of the target ($R_i sim
R_t$). This weaker decline is due to the fact that the shock hardly decelerates
when the mass swept up by the shock is comparable to the mass of the impactor
and that, in the large impactor regime, the rarefaction wave is not able to
catch up with the forward shock such that the mass contained in the shock front
is - analogous to Newton's cradle - simply the impactor mass. We use the
resulting surface velocity profiles to calculate the atmospheric mass loss for
a large range of impactor masses and impact velocities and apply them to the
Kepler-36 system and the Moon forming impact. Finally, we present and
generalise our results in terms of the $v_g/v_i$ and the impactor to target
size ratio ($R_i/R_t$) such that they can easily be applied to other collision
scenarios.
Using moving mesh hydrodynamic simulations, we determine the shock
propagation and resulting ground velocities for a planet hit by a high velocity
impactor. We use our results to determine the atmospheric mass loss caused by
the resulting ground motion due to the impact shock wave. We find that there
are two distinct shock propagation regimes: In the limit in which the impactor
is significantly smaller than the target ($R_i<< R_t$), the solutions are
self-similar and the shock velocity at a fixed point on the target scale as
$m_i^{2/3}$, where $m_i$ is the mass of the impactor, and the ground velocities
follow a universal profile given by
$v_g/v_i=(14.2x^2-25.3x+11.3)/(x^2-2.5x+1.9) +2ln{R_i/R_t}$, where
$x=sinleft(theta/2right)$, $theta$ is the latitude on the target measured
from the impact site, and $v_g$ and $v_i$ are the ground velocity and impact
velocity, respectively. In addition, we find that shock velocities decline with
the mass of the impactor significantly more weakly than $m_i^{2/3}$ in the
limit in which the impactor is comparable to the size of the target ($R_i sim
R_t$). This weaker decline is due to the fact that the shock hardly decelerates
when the mass swept up by the shock is comparable to the mass of the impactor
and that, in the large impactor regime, the rarefaction wave is not able to
catch up with the forward shock such that the mass contained in the shock front
is – analogous to Newton’s cradle – simply the impactor mass. We use the
resulting surface velocity profiles to calculate the atmospheric mass loss for
a large range of impactor masses and impact velocities and apply them to the
Kepler-36 system and the Moon forming impact. Finally, we present and
generalise our results in terms of the $v_g/v_i$ and the impactor to target
size ratio ($R_i/R_t$) such that they can easily be applied to other collision
scenarios.
http://arxiv.org/icons/sfx.gif
