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----------------- 2652 - PARKER SOLAR PROBE - new discoveries about our sun?
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- Over the next few years, the probe will swoop around the Sun several more times, getting closer to it than any spacecraft before. It will be close enough to fly through the corona, the streaky outer layers of the Sun that are visible during a total solar eclipse.
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- Researchers designed the Parker Solar Probe to withstand the high temperatures near the Sun. By flying so close to our star, the probe will help scientists better understand the corona and solar wind, the particles that stream out from the Sun and throughout the solar system.
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- Many mysteries remain about our nearest star. How the corona is so hot (millions of degrees, versus just a few thousand degrees at the Sun’s surface). How the Sun creates and pushes solar wind out into space.
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- As solar wind blows outward, it also rotates around the Sun much faster than previously thought. The reasons for this are still unknown, but the findings may have implications for how stars slow down their spinning as they age.
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- There are dramatic changes in the Sun’s magnetic fields that may be depositing energy into solar wind and speeding it up.
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- Part of the Sun’s solar wind, dubbed “slow solar wind,” whose origins aren’t completely understood, seems to come at least partly from holes in the Sun’s corona.
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- Measurements of energetic particles traveling from the Sun along its magnetic field imply that the shape of the Sun’s magnetic field could be more complex than previously thought.
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- Images taken of the corona reveal a more detailed look at its structure and at how matter leaves the Sun and makes up solar wind.
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- One of the biggest questions about the Sun’s corona and solar wind has been how the Sun transports energy out into the corona, heating it to extreme temperatures and pushing solar wind to faster speeds. Scientists have suspected that magnetic fields have something to do with it, but they didn’t know exactly how the Sun’s magnetic fields would be carrying that energy outward.
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- The Parker Solar Probe saw dramatic changes in the vibrations of magnetic fields near the Sun, which seem to lose energy going outward. Though the findings aren’t yet conclusive, it’s possible that this could be heating the Sun’s corona and accelerating solar wind.
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- Among the most feared events in space physics are solar eruptions, massive explosions that hurl millions of tons of plasma gas and radiation into space. These outbursts can be deadly: if the first moon-landing mission had encountered one, the intense radiation could have been fatal to the astronauts.
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- When eruptions reach the magnetic field that surrounds the Earth, the contact can create geomagnetic storms that disrupt cell phone service, damage satellites and knock out power grids.
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- NASA is eager to know when an eruption is coming and when what looks like the start of an outburst is just a false alarm. Knowing the difference could affect the timing of future space missions such as journeys to Mars, and show when steps to protect satellites, power systems and other equipment need to be taken.
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- Researchers have identified a mechanism that may halt eruptions before they leave the sun. The finding provides a potentially important way to distinguish the start of explosions from buildups that will fail.
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- The violent eruptions, called “coronal mass ejections,” stem from a sudden release of magnetic energy that is stored in the sun’s corona, the outermost layer of the star. This energy is often found in what are called “magnetic flux ropes,” massive arched structures that can twist and turn like earthly twine. When these long-lived structures twist and destabilize, they can either erupt out into the solar system or fail and collapse back toward the sun.
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- The researchers found in laboratory experiments that such failures occur when the guide magnetic field, a force that runs along the flux rope, is strong enough to keep the rope from twisting and destabilizing.
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- Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic force that halts the eruptions. The importance of this force, called the “toroidal field tension force,” is missing from existing models of solar eruptions.
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- The researchers discovered this importance using the Laboratory’s Magnetic Reconnection Experiment, the world’s leading device for studying how magnetic fields in plasma converge and violently snap apart. The scientists modified the device to produce both a flux rope, which stores a significant amount of energy that seeks to drive the rope outward, and a “potential magnetic field” like the ones that enclose the rope in the solar corona.
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- This potential magnetic field is composed of magnetic “strapping” and “guide” fields, each of which provides restraining forces. Eruptions burst forth when the restraining forces in the strapping field become too weak to hold the rope down, creating what is called a “torus instability” that shoots plasma into space. The guide field, which reduces the twist in the flux rope, had long been thought to be of secondary importance.
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- The guide field can play an important role in halting eruptions. When the flux rope starts to move outward in the presence of a sufficiently powerful guide field, the plasma undergoes an internal reconfiguration that causes the eruption to lose energy and collapse. The presence of a substantial guide field should therefore indicate a reduced probability of eruption.
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- Solar physicists should thus be on the lookout for guide fields, which can be found in relatively simple reconstructions of the sun’s potential magnetic field.
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- One promising candidate for study is the largest active region in the peak solar cycle that took place in October 2014, which produced many large flares but no observed eruptions. Preliminary analysis of this region shows that a number of these flares were associated with failed eruptions that could have been caused by this mechanism.
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- That lucky ol’ Sun got nothing to do but to roam around heaven all day.
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-------------------------------- Other reviews about our lucky ol’ Sun:
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- 2618 - SUN - learning closer than ever? The Solar Orbiter spacecraft, a collaboration between the European Space Agency and NASA, launched February 9, 2020. On January 29, NASA's Parker Solar Probe made its closest swing pass the sun to date, a record it will continue to break until 2025. We have been studying the sun for a thousand years. Learning is closer that ever!
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- 2613 - SUNSPOTS - The Sun is supposed to follow 11-year cycles of minimum and maximum activity that should trace set patterns pretty much like clockwork, give or take weaker and stronger sunspot patterns, flares, and periods of coronal mass ejections. That is what I learned in High School. So, what’s going on?
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------------------------------- This review 2613 lists 20 more in the appendix:
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- March 6, 2020 2652
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--------------------- Friday, March 6, 2020 -------------------------
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