  Precise measurements of exoplanets radii are of key importance for our
understanding of the origin and nature of these objects. Measurement of the
planet radii using the transit method have reached a precision that the effects
of stellar surface features have to be taken into account. While the effects
from spots have already been studied in detail, our knowledge of the effects
caused by faculae is still limited. This is particularly the case for M-stars.
Faculae can pose a problem if they are inhomogeneously distributed on the
stellar surface. Using the eclipse mapping method, we study the distribution of
the faculae on the surface of GJ1214 using the CaIIH&K lines as tracers. In
order to assess the homogeneity of the distribution in a quantitative way, we
introduce the inhomogeneity factor IHF. IHF is 0% if the distribution is
homogeneous, positive, if the plage regions are preferentially located along
the path of the planet, and negative, if they are preferentially located
outside the path of the planet. For GJ1214, we derive a rather small value of
IHF=7.7-7.7+12.0%. We discuss the relevance of this result in the context of
the PLATO and ARIEL missions.
