Sudden brightening of aurora occurs at an early phase of substorm onset. Such auroral enhancements are strongly associated with parallel currents or shear Alfven waves. With MHD wave equations, we investigate the generation of field-aligned currents near the equatorial region of the inner magnetotail, at the boundary between cold and hot plasmas. Our results show that strong localized shear Alfven waves are excited near this boundary via mode conversion when compressional input is assumed. We suggest that this boundary region is strongly associated with the auroral location.