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--------------------- 2668 - SUN - how do we learn the source of its power.?
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- Solar physics and could help predict harmful solar outbursts aimed at Earth. Called “coronal mass ejections“, these dangerous clouds of extremely energetic particles produce shimmering auroras that can bedazzle even mid-latitude skies, but they can also knock out communication satellites, take down power grids, and could be lethal for astronauts.
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- Parker Solar Probe seven-year mission will orbit the Sun 24 times. Its trajectory also takes it close to the planet Venus. These flybys decrease the probe’s orbital speed and will ultimately allow it to sail within four million miles of the sun, or eight times closer than any previous spacecraft.
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- First solar flyby Aug. 12, 2018. Nov. 5, 2018 first Venus flyby. First closest approach Oct. 3, 2018.
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- A special designed Solar-probe cup will measures speed, density, and temperature of solar wind. Thermal shield Protects the probe from temperatures nearing 2500°F. The carbon-carbon composite shield is eight feet wide and just 4.5 inches thick.
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- Carrying four instruments, the spacecraft is flying through the sun’s corona, taking measurements of the solar atmosphere and trying to sniff out the origin of the solar wind, or clouds of speedy energetic particles that the sun endlessly exhales. Getting so close to the sun is crucial, since the probe can sample the raw, pristine solar wind that we can’t easily study from Earth.
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- By the time the solar wind gets to us, it has evolved. It’s changed, it’s been processed, a lot of the structure, a lot of the things that might tell us how it originated have been smeared out or smoothed out. Parker is diving down to where it’s young, and it’s taking observations where it’s fresh.
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- Already, scientists know that the gustier, supersonic breaths originate from cold, magnetic holes in the solar corona. But the denser, slower solar wind’s origin is a mystery. So, too, is the Sun’s unfathomably hot atmosphere. While the star’s face burns at a relatively cool 10,000 degrees Fahrenheit, the upper corona burns at more than a million degrees.
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- The Sun has to be releasing some extra energy that we don’t see. And it actually has to dump that energy. So, we have to find some mechanism for throwing energy out into space before depositing it. The conservation of energy is a law in physics that requires that energy cannot be created or destroyed. It just must change from one form to another.
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- Perhaps most stunning among the initial observations are dramatic magnetic waves that sweep through the solar atmosphere, instantly increasing wind speeds by as much as 300,000 miles an hour and, in some cases, causing a complete reversal of the local magnetic field.
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- The wind is moving so fast, and shooting so violently, it actually flips the magnetic field 180 degrees around in under a second.
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- During its first two passes, the Parker Solar Probe encountered maybe a thousand of these magnetic waves, which are mammoth locally but too small to detect from Earth. They last for seconds to minutes, would completely whipsaw a normal compass, and have no obvious source.
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- These switchbacks waves are depositing energy, and could be playing a role in superheating the solar corona.
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- Also perplexing is the sideways speed of the solar wind. The Sun spins on its axis once every 24.5 Earth days, and the barrage of particles initially rotates along with it. By the time the solar wind reaches Earth, it’s traveling radially, or streaming outward like water from a rotating lawn sprinkler.
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- That makes a certain amount of sense. But when the Parker Solar Probe swung low over the sun’s southern hemisphere, it measured the solar wind’s rotational speed and found that the wind is whipping around the star much faster than anyone thought possible at such a distance. We’re missing something very fundamental about the sun’s corona and the solar wind.
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- Overly speedy winds can affect the rate at which stars evolve; newborn stars spin quickly and slow down over eons, losing energy in the form of these winds. While it’s not looking like our Sun will burn out any faster than anticipated, these strangely fast winds hint that our star may slow its rotation rate more quickly as it ages.
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- The surprising rotational speed could also be affecting predictions about the trajectories and arrival times of coronal mass ejections, the solar spasms that can take out power on Earth.
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- Often, the coronal mass ejections move in a direction we’re not expecting. If there are large flows sideways, this could be a big reason why we do a bad job predicting coronal mass ejections.
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- As the mission continues, the Parker Solar Probe will undoubtedly reveal even more surprises. For one, the spacecraft is on the verge of detecting a long-hypothesized but never-seen area around the Sun where it’s so intensely hot that “no dust can survive. This dust-free area has evaded detection since its prediction in 1928, even during solar eclipses, when the near-sun environment is much easier to see from Earth.
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- And as the solar cycle begins to ramp up from its 11-year-minimum, scientists are expecting the mission to get even more exciting.
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- Parker Space Probe has already made a few laps around the Sun. Along the way, it's brought new insights into the Sun's outer atmosphere, as well as uncovered surprising facts about the solar wind and the Sun's magnetic fields.
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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. 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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- The Parker Solar Probe is designed 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, like how the corona is so hot (millions of degrees, versus just a few thousand degrees at the Sun’s surface) and 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,” seems to come at least partly from holes in the Sun’s corona. 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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- These initial results show how information gathered by the Parker Solar Probe’s many instruments could eventually reveal some of the Sun’s remaining secrets.
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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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- Coronal mass ejections are violent eruptions that 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. Under these conditions, the guide field interacts with electric currents in the flux rope to produce a dynamic force that halts the 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.
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- The guide field, which reduces the twist in the flux rope, had long been thought to be of secondary importance. But the researchers found that 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, or “self-organization”, that causes the eruption to lose energy and collapse.
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- We are learning so much more about that lucky ol’ Sun that is roaming around the heavens and pretty much taken for granted. E are beginning to appreciate how complicated the life of a star really is. Stay tuned, there is much more to learn.
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- March 16, 2020 2668
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--------------------- Monday, March 16, 2020 --------------------
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