Heliosphere

The heliosphere is the magnetosphere, stellar wind bubble and outermost atmospheric layer of the Sun.

Diagram of features of the heliosphere. Based on preliminary results from the Interstellar Boundary Explorer.

The heliosphere is the cavity made by the Sun in the interstellar medium. Almost all of the material in the heliosphere comes from the Sun 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 the termination shock; the point where the interstellar medium and solar wind pressures balance is called the heliopause; the point where the interstellar medium, travelling in the opposite direction, slows down as it collides with the heliosphere is the bow shock.

Solar wind

Main page: Solar wind

The solar wind is made of particles. They are charged (ionized) atoms from the solar corona, and fields, in particular magnetic fields. As the Sun rotates once in about 27 days, the magnetic field transported by the solar wind gets wrapped into a spiral. Differences in the Sun's magnetic field are carried outward by the solar wind and can produce magnetic storms in the Earth's magnetosphere.

In March 2005, measurements by the Solar Wind Anisotropies (SWAN) instrument onboard the Solar 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 not axisymmetrical, but is distorted, very likely under the effect of the local galactic magnetic field.^[3]

Heliosphere Media

The Sun photographed at a wavelength of 19.3 nanometers (ultraviolet)
The heliospheric current sheet out to the orbit of Jupiter
A "termination shock" analogy of water in a sink basin.
Illustration of the heliosphere as released on 28 June 2013 which incorporates results from the Voyager spacecraft. The heliosheath is between the termination shock and the heliopause.
The bubble-like heliosphere moving through the interstellar medium.
Energetic neutral atom (ENA) detection is more concentrated in one direction.
Pioneer H, on display at the National Air and Space Museum, was a canceled probe to study the Sun.
IBEX Heliosphere Map
Overview of heliophysics spacecraft circa 2011.
Energetic neutral atoms map by IBEX. Credit: NASA / Goddard Space Flight Center Scientific Visualization Studio.