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Ambipolar diffusion likely plays a pivotal role in the formation andevolution of dense cores in weakly-ionized molecular clouds. Linear analysesshow that the evolutionary times and fragmentation scales are significantlygreater than the hydrodynamic (Jeans) values even for clouds with mildlysupercritical mass-to-flux ratio. We utilize values of fragmentation scales andgrowth times that correspond to typical ionization fractions within a molecularcloud, and apply to the context of the observed estimated lifetime ofprestellar cores as well as the observed number of such embedded cores formingin a parent clump. By varying a single parameter, the mass-to-flux ratio, overthe range of observationally measured densities, we fit the range of estimatedprestellar core lifetimes ($\sim 0.1$ to a few Myr) identified with Herschel aswell as the number of embedded cores formed in a parent clump measured inPerseus with the Submillimeter Array (SMA). Our model suggests that theprestellar cores are formed with a transcritical mass-to-flux ratio and higherdensities correspond to somewhat higher mass-to-flux ratio but the normalizedmass-to-flux ratio $\mu$ remains in the range $1 \lesssim \mu \lesssim 2$. Ourbest-fit model exhibits $B \propto n^{0.43}$ for prestellar cores, due topartial flux-freezing as a consequence of ambipolar diffusion.

Variation of the Core Lifetime and Fragmentation Scale in Molecular Clouds as an Indication of Ambipolar Diffusion