Magnetic field by that loop. Ampère's law is always valid for steady currents and can be used to calculate the -field for certain highly symmetric situations such as an infinite wire or an infinite solenoid. In a modified form that accounts for time varying electric fields, Ampère's law is one of four Maxwell's equations that describe electricity and magnetism. A charged particle moving in a -field experiences a "sideways" force that is proportional to the strength of the magnetic field, the component of the velocity that is perpendicular to the magnetic field and the charge of the particle. This force is known
Interplanetary magnetic field 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. These two magnetic domains are separated by a two current sheet (an electric current that is confined to a curved plane). This heliospheric current sheet has