When heat and mass transfer occur simultaneously in a moving fluid affecting each other causes a cross diffusion effect, the mass transfer caused by temperature gradient is called the Soret effect, while the heat transfer caused by concentration effect is called the Dufour effect. Soret and Dufour effects are important phenomena in areas such as hydrology, petrology, and geosciences.
In view of the above studies, the purpose of current investigation is to examine the influence of Soret and Dufour effects on MHD free convective heat and mass transfer flow over a vertical channel with constant suction and viscous dissipation.
It also depends on aiding and opposing mixed convection parameter ([+ or -]Gr/Re), melting parameter M, Dufour effect (Df), Soret effect (Sr), and Lewis number (Le).
 investigated the onset of the double diffusive convection in a two-component couple stress fluid layer with the Soret and Dufour effects using both linear and nonlinear stability analyses.
Also, in a process involving the coupled heat and mass diffusion, a gradient in temperature can give rise to additional mass transfer (Soret effect), and a gradient in concentration can result in additional heat transfer (Dufour effect).
The heat flux is related to the temperature gradient (Fourier's law) as well as to the gradient of the moisture content (Dufour effect).
The heat transfer caused by concentration gradient is called the diffusion thermo or Dufour effect. On the other hand mass transfer caused by temperature gradient is called Soret or thermal diffusion effect.
(5) Dufour effect is to increase both temperature and concentration distributions with formation of peak for higher values of Dufour parameter in the thermal boundary layer.
The Soret and Dufour effects
have garnered considerable interest in both Newtonian and non-Newtonian convective heat and mass transfer.
Very recently, Postelnicu  studied numerically the influence of a magnetic field on heat and mass transfer by natural convection from vertical surfaces in porous media considering Soret and Dufour effects.
Postelnicu (2004): Influence of a magnetic field on heat and mass transfer by natural convection from vertical surfaces in porous media considering Soret and Dufour effects, Int.
Postelnicu  reported the influence of magnetic field on heat and mass transfer by natural convection from vertical surfaces in porous media considering Soret and Dufour effects
. Osalusi et al.