We present a study of the magnetic field of the Small Magellanic Cloud ( SMC ) , carried out using radio Faraday rotation and optical starlight polarization data .
Consistent negative rotation measures ( RMs ) across the SMC indicate that the line-of-sight magnetic field is directed uniformly away from us with a strength 0.19 \pm 0.06 \mu G. Applying the Chandrasekhar-Fermi method to starlight polarization data yields an ordered magnetic field in the plane of the sky of strength 1.6 \pm 0.4 \mu G oriented at a position angle 4 ^ { \circ } \pm 12 ^ { \circ } , measured counter-clockwise from the great circle on the sky joining the SMC to the Large Magellanic Cloud ( LMC ) .
We construct a three-dimensional magnetic field model of the SMC , under the assumption that the RMs and starlight polarization probe the same underlying large-scale field .
The vector defining the overall orientation of the SMC magnetic field shows a potential alignment with the vector joining the center of the SMC to the center of the LMC , suggesting the possibility of a ‘ ‘ pan-Magellanic ’ ’ magnetic field .
A cosmic-ray driven dynamo is the most viable explanation of the observed field geometry , but has difficulties accounting for the observed uni-directional field lines .
A study of Faraday rotation through the Magellanic Bridge is needed to further test the pan-Magellanic field hypothesis .