Resolution of the details of a planetary magnetic field from
magnetometer measurements made during a single flyby can be
severely limited, because of the incomplete geometrical
sampling of the planetary neighborhood by the flyby
trajectory.  This problem was especially severe for the only
spacecraft encounter with Uranus, that of Voyager 2 in 1986.
Fortunately, auroras at the magnetic field-line footprints
serve as additional constraints that may be used to
determine the higher multipole moments of planetary fields
[Connerney, JGR 103:11,929, 1998].  In the present work,
this approach is applied to improving the resolution of the
magnetic field of Uranus.  The auroral emission distribution
at Uranus is determined from scans by the Voyager 2
Ultraviolet Spectrometer (UVS), enhancing an earlier
analysis [Herbert and Sandel, JGR 99:4143, 1994] by
incorporating more observations and by using more powerful
analysis techniques.  The resulting new determination of the
auroral ovals is well correlated with the field lines
associated with the strongest plasma wave and radio
emissions, but differs from model ovals computed from the Q3
magnetic field model for Uranus [Connerney et al., JGR
92:15,329, 1987].  Consequently, a search has been initiated
for model coefficients of the planetary magnetic field that
agree both with the magnetic-field observations and also
with the reasonable assumption that the newly determined
auroral emissions lie at the magnetic footprints of an
equi-distant circum-Uranian region of the magnetosphere.
The dipole and quadrupole terms of the new field model,
termed AH5, are similar to those of the dipole+quadrupole Q3
model, but the Q3 higher multipole terms diverge from the
dipole+quadrupole+octupole I3E1 model [Connerney et al.,
1987] from which the Q3 model was derived.  Inasmuch as the
I3E1 octupole terms were not resolved, the AH5 model derived
here comprises a first estimate of the higher multipole
moments of Uranus' magnetic field.