 In near-Earth space, the IMF nominally makes an angle of approximately 45° to the Earth-Sun line, though this angle varies with solar wind speed.The angle of the IMF to the radial direction reduces with helio-latitude, as the speed of the photospheric foot point is reduced.Depending on the polarity of the photospheric foot point, the heliospheric magnetic field spirals inward or outward; the magnetic field follows the same shape of spiral in the northern and southern parts of the heliosphere, but with opposite field direction.