- 3408 - PARKER SPACE PROBE - For the first time in history, a spacecraft has touched the Sun. NASA's Parker Solar Probe has now flown through the Sun's upper atmosphere , the corona, and sampled particles and magnetic fields there.
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--------------------- 3408 - PARKER SPACE PROBE
- Just as landing on the Moon allowed scientists to understand how it was formed, touching the very stuff the Sun is made of will help scientists uncover critical information about our closest star and its influence on the solar system.
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- Not only does this milestone provide us with deeper insights into our Sun's evolution and it's impacts on our solar system, but everything we learn about our own star also teaches us more about stars in the rest of the universe.
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- Parker is making new discoveries that other spacecraft were too far away to see, including from within the solar wind , the flow of particles from the Sun that can influence us at Earth.
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- In 2019, Parker discovered that magnetic zig-zag structures in the solar wind, called “switchbacks“, are plentiful close to the Sun. But how and where they form remained a mystery. Halving the distance to the Sun since then, Parker Solar Probe has now passed close enough to identify one place where they originate: the solar surface.
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- This first passage through the corona will provide data on other phenomena that are impossible to study from afar. Flying so close to the Sun, Parker Solar Probe now senses conditions in the magnetically dominated layer of the solar atmosphere - the corona - that we never could before.
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- Measurements in the corona include magnetic field data, solar wind data, and visually in images. Parker Solar Probe launched in 2018 to explore the mysteries of the Sun.
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- Unlike Earth, the Sun doesn't have a solid surface. But it does have a superheated atmosphere, made of solar material bound to the Sun by gravity and magnetic forces. As rising heat and pressure push that material away from the Sun, it reaches a point where gravity and magnetic fields are too weak to contain it.
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- That point, known as the “Alfvén critical surface“, marks the end of the solar atmosphere and beginning of the “solar wind“. Solar material with the energy to make it across that boundary becomes the solar wind, which drags the magnetic field of the Sun with it as it races across the solar system, to Earth and beyond.
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- Beyond the Alfvén critical surface, the solar wind moves so fast that waves within the wind cannot ever travel fast enough to make it back to the Sun, severing their connection.
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- Researchers were unsure exactly where the Alfvén critical surface lay. Based on remote images of the corona, estimates had put it somewhere between 10 to 20 solar radii from the surface of the Sun - 4.3 to 8.6 million miles.
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- Parker's spiral trajectory brings it slowly closer to the Sun and during the last few passes, the spacecraft was consistently below 20 solar radii (91 percent of Earth's distance from the Sun), putting it in the position to cross the boundary.
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- On April 28, 2021, during its eighth flyby of the Sun, Parker Solar Probe encountered the specific magnetic and particle conditions at 18.8 solar radii (8.1 million miles) above the solar surface that told scientists it had crossed the Alfvén critical surface for the first time and finally entered the solar atmosphere.
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- During the flyby, Parker Solar Probe passed into and out of the corona several times. This is proved that the Alfvén critical surface isn't shaped like a smooth ball. Rather, it has spikes and valleys that wrinkle the surface. Discovering where these protrusions line up with solar activity coming from the surface can help scientists learn how events on the Sun affect the atmosphere and solar wind.
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- At one point, as Parker Solar Probe dipped to just beneath 15 solar radii ( 6.5 million miles) from the Sun's surface, it transited a feature in the corona called a pseudostreamer. “Pseudostreamers” are massive structures that rise above the Sun's surface and can be seen from Earth during solar eclipses.
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- Passing through the pseudostreamer was like flying into the eye of a storm. Inside the pseudostreamer, the conditions quieted, particles slowed, and number of switchbacks dropped - a dramatic change from the busy barrage of particles the spacecraft usually encounters in the solar wind.
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- For the first time, the spacecraft found itself in a region where the magnetic fields were strong enough to dominate the movement of particles there. These conditions were the definitive proof the spacecraft had passed the Alfvén critical surface and entered the solar atmosphere where magnetic fields shape the movement of everything in the region.
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- The first passage through the corona, which lasted only a few hours, is one of many planned for the mission. Parker will continue to spiral closer to the Sun, eventually reaching as close as 8.86 solar radii (3.83 million miles) from the surface. Upcoming flybys, the next of which is happening in January , 2022, will likely bring Parker Solar Probe through the corona again.
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- The size of the corona is also driven by solar activity. As the Sun's 11-year activity cycle - the solar cycle - ramps up, the outer edge of the corona will expand, giving Parker Solar Probe a greater chance of being inside the corona for longer periods of time.
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- The origin of zig-zag-shaped structures in the solar wind, called switchbacks showed one spot that switchbacks originate is at the visible surface of the Sun - the “photosphere“.
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- By the time it reaches Earth, 93 million miles away, the solar wind is an unrelenting headwind of particles and magnetic fields. But as it escapes the Sun, the solar wind is structured and patchy.
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- In the mid-1990s, the NASA-European Space Agency mission Ulysses flew over the Sun's poles and discovered a handful of bizarre S-shaped kinks in the solar wind's magnetic field lines, which detoured charged particles on a zig-zag path as they escaped the Sun.
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- In 2019, at 34 solar radii from the Sun, Parker discovered that switchbacks were not rare, but common in the solar wind. Where were they coming from? Were they forged at the surface of the Sun, or shaped by some process kinking magnetic fields in the solar atmosphere?
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- The new findings finally confirm one origin point is near the solar surface. Data showed switchbacks occur in patches and have a higher percentage of helium - known to come from the photosphere - than other elements.
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- The switchbacks' origins were further narrowed when the scientists found the patches aligned with magnetic funnels that emerge from the photosphere between convection cell structures called “super granules“.
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- The scientists think the magnetic funnels might be where one component of the solar wind originates. The solar wind comes in two different varieties - fast and slow - and the funnels could be where some particles in the fast solar wind come from.
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- The structure of the regions with switchbacks matches up with a small magnetic funnel structure at the base of the corona. Understanding where and how the components of the fast solar wind emerge, and if they're linked to switchbacks, could help scientists answer a longstanding solar mystery: how the corona is heated to millions of degrees, far hotter than the solar surface below.
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- How are switchbacks formed? One theory suggests they might be created by waves of plasma that roll through the region like ocean surf. Another contends they're made by an explosive process known as magnetic reconnection, which is thought to occur at the boundaries where the magnetic funnels come together.
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- The data to come will allow scientists a glimpse into a region that's critical for superheating the corona and pushing the solar wind to supersonic speeds. Such measurements from the corona will be critical for understanding and forecasting extreme space weather events that can disrupt telecommunications and damage satellites around Earth.
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- It's really exciting to see our advanced technologies succeed in taking Parker Solar Probe closer to the Sun than we've ever been, and to be able to return such amazing science
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- Parker Solar Probe is part of NASA's Living with a Star program to explore aspects of the Sun.-Earth system that directly affect life and society.
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January 12, 2022 PARKER SPACE PROBE 3408
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