heliosheathn.
/ˈhiːlɪəʃiːθ/, U.S. /ˈhiliəˌʃiθ/, /ˈhiljəˌʃiθ/ Astronomy.
The outermost region of the heliosphere, in which the speed of the solar wind is subsonic. Cf. termination shock n. at termination n. Compounds.
ΚΠ
1970 K. H. Schatten & J. M. Wilcox Proc. 11th Internat. Conf. Cosmic Rays 1969 in Acta Physica Acad. Sci. Hungaricae 29 Suppl. II. 282 We shall define the heliosheath to mean this region where the solar wind magnetic field and the interstellar field merge.
2003 Science 27 June 2005 A shear velocity instability forms just beyond the termination shock, causing a jet and sheetlike feature to oscillate up and down in the heliosheath.
2008 Sci. Amer. (U.K. ed.) Mar. 18/1 Mapping the thickness of the heliosheath will be the goal of the new spacecraft IBEX, planned for a mid-July launch.
This is a new entry (OED Third Edition, March 2017; most recently modified version published online March 2022).
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n.1970