  Solar UV emission has a profound impact on the upper terrestrial atmosphere.
Because of instrumental constraints, however, solar proxies often need to be
used as substitutes for the solar spectral variability. Finding proxies that
properly reproduce specific spectral bands or lines is an ongoing problem.
Using daily observations from 2003 to 2008 and a multiscale statistical
approach, we test the performances of 9 proxies for the UV solar flux. Their
relevance is evaluated at different time-scales and a novel representation
allows all quantities to be compared simultaneously. This representation
reveals which proxies are most appropriate for different spectral bands and for
different time scales.
