  High-resolution coherent x-ray diffraction experiment has been performed on
the charge density wave (CDW) system K$_{0.3}$MoO$_3$. The $2k_F$ satellite
reflection associated with the CDW has been measured with respect to external
dc currents. In the sliding regime, the $2k_F$ satellite reflection displays
secondary satellites along the chain axis which corresponds to correlations up
to the micrometer scale. This super long range order is 1500 times larger than
the CDW period itself. This new type of electronic correlation seems inherent
to the collective dynamics of electrons in charge density wave systems. Several
scenarios are discussed.
