  We construct a ``logarithmic'' cohomology operation on Morava E-theory, which
is a homomorphism defined on the multiplicative group of invertible elements in
the ring E^0(K) of a space K. We obtain a formula for this map in terms of the
action of Hecke operators on Morava E-theory. Our formula is closely related to
that for an Euler factor of the Hecke L-function of an automorphic form.
