Matter-Enhanced Neutrino Oscillations in the Quasi-Adiabatic Limit

We introduce simple analytic expressions for the neutrino survival probability in media valid in the quasi-adiabatic limit. These expressions provide a quick but accurate alternative to numerical solution of the neutrino propagation equations for the Mikheyev-Smirnov-Wolfenstein effect. They can also be used to extract information about the density scale height from the neutrino data. As an example, we present calculations for solar neutrinos.