Radial polarization orientation generated by a vertical beam of particles moving along vertical magnetic field lines. These particles are supposed to have velocities close to the electron Na D2 collisional excitation threshold-velocity . Line-of-sight and particle beam directions are perpendicular to solar disk and to solar surface, respectively. The linear polarization direction is in a plane defined by the beam and line-of-sight directions. By projection onto the solar disk, this polarization appears to be radial. Higher energy particles generate tangential polarization, so perpendicular to the radial direction.