  A proxy for horizontal electric currents in the solar photosphere was
suggested. For a set of evolving active regions (ARs) observed with {\it Solar
and Heliospheric Observatory (SOHO)} Michelson Doppler Imager (MDI) in the high
resolution mode, the dissipation spectrum, $k^2E(k)$, and the spatial structure
of dissipation, i.e., the Stokes dissipation function $\epsilon(x,y)$, were
calculated from the observed $B_z$ component of the magnetic field. These
functions allowed us to calculate (a part of) the horizontal electric current
density in the photosphere. It was shown that as an active region emerges,
large-scale horizontal electric currents are gradually generated and determine
a bulk of dissipation. When an active region decays, the large-scale horizontal
currents decay faster than the small-scale ones. The density of horizontal
currents in active regions is in the range of $<j_h > \sim (0.008 - 0.028)$
A/m$^2$, that is compatible with the density of vertical currents in active
regions. We suggest two possible mechanisms for generation of such horizontal
currents in the photosphere. One of them is the drift motions of charged
particles in the medium of varying plasma pressure gradient in a horizontal
plane at the periphery of a sunspot. Such a drift can produce quasi-circular
closed horizontal currents around sunspots. Another possibility could be an
existence of horizontal axial current inside a highly twisted horizontal
magnetic structure laying in the photosphere along the magnetic neutral line.
The horizontal currents may contribute significantly to the dynamics of the
photosphere/corona coupling, as well as the estimation of non-potentiality of
ARs.
