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Earth's Magnetosphere - presented by Science@NASA
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Enveloping our planet, and protecting us from the fury of the Sun, is a giant bubble of magnetism called the magnetosphere.
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It deflects most of the solar material sweeping towards us from our star, at 1 million miles per hour or more.
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Without the magnetosphere, the relentless action of these solar particles could strip the Earth of its protective layers, which shield us from the Sun's ultraviolet radiation.
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It's clear that this magnetic bubble was key to helping Earth develop into a habitable planet.
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Compare Earth to Mars, a planet that lost its magnetosphere about 4.2 billion years ago.
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The Solar wind is thought to have stripped away most of Mars' atmosphere, possibly after the red planet's magnetic field dissipated.
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This has left Mars as the stark, barren world we see today through the 'eyes' of NASA orbiters and rovers.
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By contrast, Earth's magnetosphere seems to have kept our atmosphere protected.
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Eftyhia Zesta, of the Geospace Physics Laboratory at NASA's Goddard Space Flight Center notes,
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"If there were no magnetic field, we might have a very different atmosphere left, without life as we know it."
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Understanding our magnetosphere is a key element to helping scientists someday forecast space weather that can affect Earth's technology.
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Extreme space weather events can disrupt communications networks, GPS navigation, and electrical power grids.
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The magnetosphere is a permeable shield.
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The solar wind will periodically connect to the magnetosphere forcing it to reconfigure.
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This can create a rift, allowing energy to pour into our safe haven.
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These rifts open and close many times daily or even many times hourly.
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Most of them are small and short-lived; others are vast and sustained.
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With the Sun's magnetic field connecting to Earth's in this way, the fireworks start.
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Zesta says, "The Earth's magnetosphere absorbs the incoming energy from the solar wind,
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and explosively releases that energy in the form of geomagnetic storms and substorms."
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How does this happen?
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Magnetic lines of force converge and reconfigure, resulting in magnetic energy and charged-particles flying off at intense speeds.
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Scientists have been trying to learn why this crisscrossing of magnetic field lines,
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called magnetic reconnection, triggers such a violent explosion, opening the rifts into the magnetosphere.
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NASA's Magnetospheric Multiscale Mission, or MMS, was launched in March 2015
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to observe the electron physics of magnetic reconnection for the first time.
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Bristling with energetic particle detectors and magnetic sensors,
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the four MMS spacecraft flew in close formation to areas on the front side of Earth's magnetosphere, where magnetic reconnection occurs.
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MMS has since been conducting a similar hunt in the magnetosphere's tail.
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MMS complements missions from NASA and partner agencies, such as THEMIS, Cluster, and Geotail, contributing critical new details to the ongoing study of Earth's magnetosphere.
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Together, data from these investigations not only help unravel the fundamental physics of space, but also help improve space weather forecasting.
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For more on the active space that surrounds Earth, stay tuned to science.nasa.gov.