function ret = magneticFieldForMOT(this, r)
    switch this.SimulationMode
        case '2D'
            ret     = zeros(1,4);
            alpha   = this.MagneticGradient;
            ret(1)  = r(3)*alpha;
            ret(2)  = 0;
            ret(3)  = r(1)*alpha;
            ret(4)  = sqrt(ret(1)^2+ret(2)^2+ret(3)^2);
        case '3D'
            % Development in progress
            
    end
end