| Term: | Heliosphere |
| Definition: |
The vast, three-dimensional region of space around the Sun filled with the solar wind and the remnant of the solar magnetic field carried in it. It is bounded by the heliopause, which is estimated to be 100 astronomical units or more from the Sun. The radius of the heliosphere is expected to vary with the solar cycle. The heliosphere may be very elongated owing to the presence of an interstellar wind of neutral hydrogen flowing from the direction of the Galactic center. |