  We present new radio/millimeter measurements of the hot magnetic star HR5907
obtained with the VLA and ALMA interferometers. We find that HR5907 is the most
radio luminous early type star in the cm-mm band among those presently known.
Its multi-wavelength radio light curves are strongly variable with an amplitude
that increases with radio frequency. The radio emission can be explained by the
populations of the non-thermal electrons accelerated in the current sheets on
the outer border of the magnetosphere of this fast rotating magnetic star. We
classify HR5907 as another member of the growing class of strongly magnetic
fast rotating hot stars where the gyro-synchrotron emission mechanism
efficiently operates in their magnetospheres. The new radio observations of
HR5907 are combined with archival X-ray data to study the physical condition of
its magnetosphere. The X-ray spectra of HR5907 show tentative evidence for the
presence of non-thermal spectral component. We suggest that non-thermal X-rays
originate a stellar X-ray aurora due to streams of non-thermal electrons
impacting on the stellar surface. Taking advantage of the relation between the
spectral indices of the X-ray power-law spectrum and the non-thermal electron
energy distributions, we perform 3-D modeling of the radio emission for HR5907.
The wavelength-dependent radio light-curves probe magnetospheric layers at
different heights above the stellar surface. A detailed comparison between
simulated and observed radio light-curves leads us to conclude that the stellar
magnetic field of HR5907 is likely non-dipolar, providing further indirect
evidence of the complex magnetic field topology of HR5907.
