The eastward flow of the equatorial counter current can be explained by the convergence of the two equatorial currents.

The two equatorial currents, the North Equatorial Current and the South Equatorial Current, flow in opposite directions on either side of the equator. The North Equatorial Current flows from east to west in the northern hemisphere, while the South Equatorial Current flows from west to east in the southern hemisphere.

When these two currents meet near the equator, they converge and create a region where the water from both currents is forced to flow in the same direction. This region is known as the equatorial counter current.

The convergence of the two equatorial currents is primarily caused by the Earth's rotation on its axis. As the Earth rotates, the Coriolis effect comes into play, causing the water to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This deflection creates a pressure gradient that drives the flow of water in the equatorial region.

The occurrence of the belt of calm near the equator, known as the doldrums, also contributes to the eastward flow of the equatorial counter current. In this region, the trade winds from the northern and southern hemispheres meet and cancel each other out, resulting in weak or variable winds. This lack of wind allows the equatorial counter current to flow relatively unimpeded.

The difference in salinity of water does not directly explain the eastward flow of the equatorial counter current. Salinity refers to the concentration of dissolved salts in water, and it can affect the density of water. However, in the case of the equatorial counter current, the primary driving force is the convergence of the two equatorial currents caused by the Earth's rotation and the doldrums.

In summary, the eastward flow of the equatorial counter current is primarily explained by the convergence of the two equatorial currents, which is caused by the Earth's rotation and the occurrence of the belt of calm near the equator.