  We introduce the notion, and develop the theory of local-noise spectroscopy
(LNS) - a tool to study the properties of systems far from equilibrium by means
of flux density correlations. As a test bed, we apply it to biased molecular
junctions. This tool naturally extends those based on local fluxes, while
providing complementary information on the system. As examples of the rich
phenomenology that one can study with this approach, we show that LNS can be
used to yield information on microscopic properties of bias-induced light
emission in junctions, provide local resolution of intra-system interactions,
and employed as a nano-thermometry tool. Although LNS may, at the moment, be
difficult to realize experimentally, it can nonetheless be used as a powerful
theoretical tool to infer a wide range of physical properties on a variety of
systems of present interest.
