  The non-thermal radio emission of main-sequence early-type stars is a
signature of stellar magnetism. We present multi-wavelength (1.6-16.7 GHz) ATCA
measurements of the early-type magnetic star rho OphC, which is a flat-spectrum
non-thermal radio source. The rho OphC radio emission is partially circularly
polarized with a steep spectral dependence: the fraction of polarized emission
is about 60% at the lowest frequency sub-band (1.6 GHz) while is undetected at
16.7 GHz. This is clear evidence of coherent Auroral Radio Emission (ARE) from
the rho OphC magnetosphere. Interestingly, the detection of the rho OphC's ARE
is not related to a peculiar rotational phase. This is a consequence of the
stellar geometry, which makes the strongly anisotropic radiation beam of the
amplified radiation always pointed towards Earth. The circular polarization
sign evidences mainly amplification of the ordinary mode of the electromagnetic
wave, consistent with a maser amplification occurring within dense regions.
This is indirect evidence of the plasma evaporation from the polar caps, a
phenomenon responsible for the thermal X-ray aurorae. rho OphC is not the first
early-type magnetic star showing the O-mode dominated ARE but is the first star
with the ARE always on view.
