  We calculate the mass loss driven by MHD waves from hot Jupiters by using MHD
simulations in one-dimensional flux tubes. If a gaseous planet has magnetic
field, MHD waves are excited by turbulence at the surface, dissipate at the
upper atmosphere, and drive gas outflows. Our calculation shows that mass loss
rates are comparable to the observed mass loss rates of hot Jupiters, therefore
it is suggested that gas flow driven by MHD waves can plays an important role
in the mass loss from gaseous planets. The mass loss rate varies dramatically
with radius and mass of a planet: a gaseous planet with a small mass but with
inflated radius produces very large mass loss rate. We also derive an
analytical expression for the dependence of mass loss rate on planet radius and
mass that is in good agreement with the numerical calculation. The mass loss
rate also depends on the amplitude of velocity dispersion at the surface of a
planet. Thus we expect to infer the condition of the surface and the internal
structure of a gaseous planet from future observations of mass loss rate from
various exoplanets.
