  Solar neutrino oscillations with wavelengths comparable to the Earth-Sun
distance provide a viable explanations of the long-standing solar neutrino
deficit. They imply a time-dependent modulation of the solar neutrino flux due
to the eccentricity of the Earth orbit. Motivated by this testable prediction,
we propose a Fourier analysis of the signal observable in real-time, solar
neutrino experiments. We give the general expressions of the Fourier
coefficients and of their correlated uncertainties in the presence of
background. The expressions assume a particularly compact form in the case of
two-flavor neutrino oscillations in vacuum. We discuss the sensitivity to the
lowest harmonics of the new-generation, high-statistics experiments
SuperKamiokande, Sudbury Neutrino Observatory, and Borexino.
