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A new time series of high-resolution Stokes I and V spectra of the magneticB2V star HD 184927 has been obtained in the context of the Magnetism in MassiveStars (MiMeS) Large Program with the ESPaDOnS spectropolarimeter at theCanada-France-Hawaii Telescope and dimaPol liquid crystal spectropolarimeter at1.8-m telescope of Dominion Astrophysical Observatory. We model the optical andUV spectrum obtained from the IUE archive to infer the stellar physicalparameters. Using magnetic field measurements we derive an improved rotationalperiod of 9.53102+-0.0007d. We infer the longitudinal magnetic field from linesof H, He and various metals, revealing large differences between the apparentfield strength variations determined from different elements. Magnetic DopplerImaging using He and O lines yields strongly nonuniform surface distributionsof these elements. We demonstrate that the diversity of longitudinal fieldvariations can be understood as due to the combination of element-specificsurface abundance distributions in combination with a surface magnetic fieldthat is comprised of dipolar and quadrupolar components. We have reanalyzed IUEhigh resolution spectra, confirming strong modulation of wind-sensitive Civ andSiv resonance lines. However, we are unable to detect any modulation of theH$\alpha$ profile attributable to a stellar magnetosphere. We conclude that HD184927 hosts a centrifugal magnetosphere, albeit one that is undetectable atoptical wavelengths. The magnetic braking timescale of HD 184927 is computed tobe $\tau_J = 0.96$ or $5.8$ Myr. These values are consistent with the slowrotation and estimated age of the star.

The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927