Solar wind

Assembled from 11 blocks · 2 evidence · 5 related

1. Story
2. The continuous outflow of charged particles — mostly protons and electrons, with a minority of helium nuclei — escaping the Sun's corona in all directions and dragging the Sun's magnetic field out with it. It leaves the Sun supersonically, at speeds of several hundred kilometres per second, and thins out as it expands, so its density falls roughly as the inverse square of distance. It is the wind that inflates the heliosphere: the volume the solar wind fills is, by definition, the volume in which the Sun rather than the Galaxy sets the local plasma conditions. Voyager 1 lost the ability to measure it directly when its plasma science instrument failed in 1980; Voyager 2 kept that instrument working, which is why the 2018 crossing has a plasma measurement and the 2012 crossing had to be inferred another way. Not a place.
3. Knowledge
4. Solar wind
5. Connections
6. Heliosphere
7. Termination shock
8. Voyager 1 crosses the termination shock at about 94 AU
9. Evidence
10. Voyager 2 crossed the heliopause on 5 November 2018 at 119 AU; a boundary layer about 1.5 AU wide preceded it in which the plasma slowed, heated and was roughly twice as dense as typical heliosheath plasma; the transition took less than a day, and the interstellar plasma immediately outside was hotter than predicted, of order 30,000–50,000 °C against a prediction nearer 15,000–30,000 °C. V55 verification basis: the paper was not fetched — nature.com is blocked to this session — but search results carried these figures and attributed them to it.
11. Voyager 1 crossed the solar wind termination shock on 16 December 2004 at about 94 AU and entered the heliosheath. V55 verification basis: NOT CHECKED IN THIS RUN. The session's search budget was exhausted before this crossing could be searched and the publisher domain is blocked; the citation is given from standard mission record without page numbers precisely because they were not confirmed. A curator must verify the date, the distance and the citation before publication.