  The thermal phase curve of 55 Cancri e is the first measurement of the
temperature distribution of a tidally locked Super-Earth, but raises a number
of puzzling questions about the planet's climate. The phase curve has a high
amplitude and peak offset, suggesting that it has a significant eastward
hot-spot shift as well as a large day-night temperature contrast. We use a
general circulation model to model potential climates, and investigate the
relation between bulk atmospheric composition and the magnitude of these
seemingly contradictory features. We confirm theoretical models of tidally
locked circulation are consistent with our numerical model of 55 Cnc e, and
rule out certain atmospheric compositions based on their thermodynamic
properties. Our best-fitting atmosphere has a significant hot-spot shift and
day-night contrast, although these are not as large as the observed phase
curve. We discuss possible physical processes which could explain the
observations, and show that night-side cloud formation from species such as SiO
from a day-side magma ocean could potentially increase the phase curve
amplitude and explain the observations. We conclude that the observations could
be explained by an optically thick atmosphere with a low mean molecular weight,
a surface pressure of several bar and a strong eastward circulation, with
night-side cloud formation a possible explanation for the difference between
our model and the observations.
