Theheliosphere is the cavity made by the Sun in theinterstellar medium. Almost all of the material in the heliosphere comes from theSun itself.
For the first ten billion kilometres of its radius, the solar wind travels at over a million kilometres per hour.[1][2] It slows down before finally stopping altogether. The point where the solar wind slows down is thetermination shock; the point where the interstellar medium and solar wind pressures balance is called theheliopause; the point where the interstellar medium, travelling in the opposite direction, slows down as it collides with the heliosphere is thebow shock.
The solar wind is made of particles. They are charged (ionized) atoms from the solarcorona, and fields, in particularmagnetic fields. As the Sunrotates once in about 27 days, the magnetic field transported by thesolar wind gets wrapped into a spiral. Differences in the Sun's magnetic field are carried outward by the solar wind and can producemagnetic storms in the Earth'smagnetosphere.
In March 2005, measurements by the Solar Wind Anisotropies (SWAN) instrument onboard theSolar and Heliospheric Observatory (SOHO) showed that the heliosphere, the solar wind-filled volume which prevents the solar system from becoming embedded in the local (ambient) interstellar medium, is notaxisymmetrical, but is distorted, very likely under the effect of the local galactic magnetic field.[3]
