A supersonic flow of ionized particles emanating from the sun
The solar wind is a supersonic ionized gas called a plasma produced by the sun that defines the region of influence in the interstellar medium of the sun, called the heliosphere. The solar wind is composed of ~94% protons, ~4-5% alpha-particles, and ≤ 1% heavy ions. Its speed is largely dependent upon the latitude of the sun from which it was emitted, where higher latitudes generally have higher flow speeds. This is thought to be due to the configuration of the magnetic fields in the solar corona. Near the equator, the field topologies are primarily closed loops while at the poles they are effectively open (i.e., they extend to the outer heliosphere allowing particles to stream along the fields). How the solar wind is accelerated and heated are still open questions. The importance of these questions resulted in NASA funding a new mission, Solar Probe Plus, to determine how the solar wind is accelerated.