further accelerates ions away from the Sun. The total number of particles carried away from the Sun by the solar wind is about per second. Thus, the total mass loss each year is about solar masses, or about 1.3–1.9 Million tonnes per second. This is equivalent to losing a mass equal to the Earth every 150 million years. However, since the Sun's formation, only about 0.01% of its initial mass has been lost through the solar wind. Other stars have much stronger stellar winds that result in significantly higher mass-loss rates. Properties and structure Fast and slow solar wind The solar wind is observed to exist in two fundamental states, termed the slow solar wind and the fast solar wind, though their differences extend well beyond their speeds. In near-Earth space, the slow solar wind is observed to have a velocity of , a temperature of ~100 MK and a composition that is a close match to the corona. By contrast, the fast solar wind has a typical velocity of , a temperature of 800 MK and it nearly matches the composition of the Sun's photosphere. The slow solar wind is twice as dense and more variable in nature than the fast solar wind. The slow solar wind appears to originate from a region around the Sun's equatorial belt that is known as the "streamer belt", where coronal streamers are produced by magnetic flux open to the heliosphere draping over closed magnetic loops. The exact coronal structures involved in slow solar wind formation and the method by which the material is released is still under debate. Observations of the Sun between 1996 and 2001 showed that emission of the slow solar wind occurred at latitudes up to 30–35° during the solar minimum (the period of lowest solar activity), then expanded toward the poles as the solar cycle approached maximum. At solar maximum, the poles were also emitting a slow solar wind. The fast solar wind originates from coronal holes, which are funnel-like regions of open field lines in the Sun's magnetic field. Such open lines are particularly prevalent around the Sun's magnetic poles. The plasma source is small magnetic fields created by convection cells in the solar atmosphere. These fields confine the plasma and transport it into the narrow necks of the coronal funnels, which are located only 20,000 km above the photosphere. The plasma is released into the funnel