![]() ![]() Such bow shocks also form around airplanes, rockets, or the Space Shuttle when these vehicles travel faster than the speed of sound in the atmosphere. In fact, its speed is so great that "bow shocks" form whenever it is forced to flow around the planets in the solar system. This extension of the Sun's magnetic field into space greatly influences the manner in which the solar wind interacts with planets and, eventually, the interstellar medium.Īs it travels through space, the solar wind reaches speeds of over one million miles per hour. When the solar wind plasma leaves the Sun's corona, it carries with it some of that yellow star's magnetic field. Earth's magnetic shield has similar topography: magnetic field lines, a magnetosheath, and magnetopause. This subsonic flow region is called the heliosheath, which extends to the heliopause, the boundary where the heliosphere meets the interstellar medium. At this point, it passes through a shock wave, called the "termination shock," and becomes subsonic (slows down). It can then no longer resist the inward push of the instellar space medium (the part of our galaxy that lies between the stars). This bubble extends far beyond the orbit of most planets in our solar system.Īs the solar wind projects further and further outward from the Sun, it spreads itself thin. Projecting outward, the solar wind forms an immense "bubble" around the Sun, called the heliosphere. They extend so far that they form an interplanetary magnetic field (IMF), which surrounds all the planets in our solar system!Ībove the Sun's active sunspot regions (dark areas caused by magnetic disturbances) on the surface, or photospheric layer, loops of magnetic field lines trap some plasma and hold it back. The magnetic field lines of these coronal holes extend outwards, their ends dragged by the solar wind. Such emissions, or streamers, are thought to come from large bright patches called "coronal holes" in the Sun's corona, as seen in the image above. As the Sun rotates (once every 27 days), it winds up its magnetic field lines above its polar regions into a large rotating spiral, creating a constant stream of "wind." It then travels along the Sun's magnetic field lines that extend radially outward. This plasma is continually heated to the point that the Sun's gravity can't hold it down. The solar wind is created by the outward expansion of plasma (a collection of charged particles) from the Sun's corona (outermost atmosphere). ![]()
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