Editing Magnetosphere (section)

===Bow shock===
[[File:Red Giant Plunging Through Space.jpg|thumb|[[Thermographic camera|Infrared image]] and artist's concept of the bow shock around [[R Hydrae]]]]
{{main|Bow shock}}
The bow shock forms the outermost layer of the magnetosphere; the boundary between the magnetosphere and the surrounding medium. For stars, this is usually the boundary between the [[stellar wind]] and [[interstellar medium]]; for planets, the speed of the solar wind there decreases as it approaches the magnetopause.<ref>{{cite arXiv|last1=Sparavigna|first1=A.C.|last2=Marazzato|first2=R.|title=Observing stellar bow shocks|date=10 May 2010|class=physics.space-ph |eprint=1005.1527}}</ref> Due to interactions with the bow shock, the [[stellar wind]] [[Plasma (physics)|plasma]] gains a substantial [[anisotropy]], leading to various [[plasma instabilities]] upstream and downstream of the bow shock. <ref>{{cite journal|last1=Pokhotelov|first1=D.|last2=von Alfthan|first2=S.|last3=Kempf|first3=Y.|last4=Vainio|first4=R.|display-authors=et al. |title= Ion distributions upstream and downstream of the Earth's bow shock: first results from Vlasiator| journal=Annales Geophysicae|date=2013-12-17|volume=31|issue=12 |pages=2207–2212|doi=10.5194/angeo-31-2207-2013|doi-access=free |bibcode=2013AnGeo..31.2207P }}</ref>