  We present a novel method to search for structures of coherently aligned
patterns in ultra-high energy cosmic-ray arrival directions simultaneously
across the entire sky. This method can be used to obtain information on the
Galactic magnetic field, in particular the integrated component perpendicular
to the line of sight, from cosmic-ray data only. Using a likelihood-ratio
approach, neighboring cosmic rays are related by rotatable, elliptically shaped
density distributions and the significance of their alignment with respect to
circular distributions is evaluated. In this way, a vector field tangential to
the celestial sphere is fitted which approximates the local deflections in
cosmic magnetic fields if significant deflection structures are detected. The
sensitivity of the method is evaluated on the basis of astrophysical
simulations of the ultra-high energy cosmic-ray sky, where a discriminative
power between isotropic and signal-induced scenarios is found.
