  We study a resonant interaction of an elliptically polarized light wave with
$^{87}$Rb vapor (D$_1$ line) exposed to a transverse magnetic field. A
$5$$\times$$5$$\times$$5$~mm$^3$ glass vapor cell is used for the experiments.
The wave intensity is modulated at the frequency $\Omega_m$. By scanning
$\Omega_m$ near the Larmor frequency $\Omega_L$, a magnetic resonance (MR) can
be observed as a change in the ellipticity parameter of the wave polarization.
This method for observing MR allows to significantly improve the
signal-to-noise ratio compared to a classical Bell-Bloom scheme using a
circularly polarized wave. The sensitivity of the magnetic field sensor is
estimated to be $\approx\,$$130$~fT/$\surd$Hz in a $2$~kHz bandwidth,
confidently competing with widely used Faraday-rotation Bell-Bloom schemes. The
results can be used to develop a miniature all-optical magnetic field sensor
for medicine and geophysics.
