The boundary where the solar wind of the sun encounters the interstellar medium and stagnates
The heliosphere top, also known as the solar wind top, is an astronomical expression derived fromsunlightOfsolar windThe boundary of stagnation when encountering the interstellar medium.120 heliosphere top radiiAstronomical unit, thickness 0.5 AU.
The heliosphere tops into seismic waves called terminal waves of the solar wind.
The bubbles blown by the solar wind in the interstellar medium (hydrogen and helium gas from the Milky Way) are calledHeliosphereOutside the boundary of the bubble is the interstellar medium that weakens the speed of the solar wind.The boundary that the solar wind can finally reach in the interstellar medium is called the heliospheric top, and is considered to besolar systemThe outer boundary of the.
Solar wind particles will be reduced from supersonic to subsonic, and from supersonic to interstellar mediumSubsonic speedThe area of is calledheliosheath ，heliosheath The inner layer of is called terminalseismic wavesThe outer layer is called the heliospheric top layer.
Outside the heliosphere top, the interaction between the interstellar medium and the heliosphere top generates bow waves in front of the sun's direction of advance.
In archseismic wavesThere is a layer between the heliosphere and the heliosphere, becauseInterstellar matterAnd the edge of the heliosphere tophydrogenHydrogen wall.
Position detection
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The heliospheric zenith is assumed to be relatively small in front of the orbit around the Milky Way, and its size will besolar windIt is known that the farthest place is beyond the orbit of the dwarf planet Pluto.According to NASA's announcementVoyager 1andVoyager 2On May 24, 2005 and May 23, 2006, the terminal seismic waves arrived successively, and we are looking forward to the arrival of both detectors at the heliosphere top.On the other hand, the interstellar boundary exploration (IBEX) is expected to be launched in 2008, reaching the heliosphere top and transmitting back images within two years.
nearheliosheath Voyager 1, 2 andPioneer 10When particles emitted by the sun encounter interstellar objects, they will slow down and releaseenergy。Many particles accumulate near the heliosphere topenergyImpact causedwave。
Another alternative or acceptable definition of heliospheric zenith is:solar systemThe region where the magnetopause of the magnetosphere meets the plasma of the Milky Way.
Detection results
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NASA's measurement tools confirmed that Voyager 1 flew out of the top of the heliosphere and finally learned the exact volume of the solar system.Its thickness is about 0.5 astronomical unit (1 astronomical unit is the average distance from the earth to the sun, about 150 million kilometers), and 120 astronomical units from the sun.
