  Simultaneous measurement of line-of-sight (LOS) magnetic and velocity fields
at the photosphere and chromosphere are presented. Fe I line at $\lambda6569$
and $H_{\alpha}$ at $\lambda6563$ are used respectively for deriving the
physical parameters at photospheric and chromospheric heights. The LOS magnetic
field obtained through the center-of-gravity method show a linear relation
between photospheric and chromospheric field for field strengths less than 700
G. But in strong field regions, the LOS magnetic field values derived from
$H_{\alpha}$ are much weaker than what one gets from the linear relationship
and also from those expected from the extrapolation of the photospheric
magnetic field. We discuss in detail the properties of magnetic field observed
in $H_{\alpha}$ from the point of view of observed velocity gradients. The
bisector analysis of $H_{\alpha}$ Stokes $I$ profiles show larger velocity
gradients in those places where strong photospheric magnetic fields are
observed. These observations may support the view that the stronger fields
diverge faster with height compared to weaker fields.
