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  • richardmitnick 9:09 am on June 22, 2019 Permalink | Reply
    Tags: , PUNCH mission, Solar research, , TRACERS mission   

    From NASA: “NASA Selects Missions to Study Our Sun, Its Effects on Space Weather” 

    NASA image
    From NASA

    June 20, 2019

    Grey Hautaluoma
    Headquarters, Washington
    202-358-0668
    grey.hautaluoma-1@nasa.gov

    Karen Fox
    Headquarters, Washington
    301-286-6284
    karen.c.fox@nasa.gov

    1
    A constant outflow of solar material streams out from the Sun, depicted here in an artist’s rendering. On June 20, 2019, NASA selected two new missions – the Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission and Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) – to study the origins of this solar wind and how it affects Earth. Together, the missions support NASA’s mandate to protect astronauts and technology in space from such radiation. Credits: NASA

    NASA has selected two new missions to advance our understanding of the Sun and its dynamic effects on space. One of the selected missions will study how the Sun drives particles and energy into the solar system and a second will study Earth’s response.

    The Sun generates a vast outpouring of solar particles known as the solar wind, which can create a dynamic system of radiation in space called space weather. Near Earth, where such particles interact with our planet’s magnetic field, the space weather system can lead to profound impacts on human interests, such as astronauts’ safety, radio communications, GPS signals, and utility grids on the ground. The more we understand what drives space weather and its interaction with the Earth and lunar systems, the more we can mitigate its effects – including safeguarding astronauts and technology crucial to NASA’s Artemis program to the Moon.

    2
    NASA’s Artemis spacecraft. The Planetary Society

    “We carefully selected these two missions not only because of the high-class science they can do in their own right, but because they will work well together with the other heliophysics spacecraft advancing NASA’s mission to protect astronauts, space technology and life down here on Earth,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “These missions will do big science, but they’re also special because they come in small packages, which means that we can launch them together and get more research for the price of a single launch.”

    PUNCH

    The Polarimeter to Unify the Corona and Heliosphere, or PUNCH, mission will focus directly on the Sun’s outer atmosphere, the corona, and how it generates the solar wind.

    3
    PUNCH four satellites

    Composed of four suitcase-sized satellites, PUNCH will image and track the solar wind as it leaves the Sun. The spacecraft also will track coronal mass ejections – large eruptions of solar material that can drive large space weather events near Earth – to better understand their evolution and develop new techniques for predicting such eruptions.

    These observations will enhance national and international research by other NASA missions such as Parker Solar Probe, and the upcoming ESA (European Space Agency)/NASA Solar Orbiter, due to launch in 2020. PUNCH will be able to image, in real time, the structures in the solar atmosphere that these missions encounter by blocking out the bright light of the Sun and examining the much fainter atmosphere.

    Together, these missions will investigate how the star we live with drives radiation in space. PUNCH is led by Craig DeForest at the Southwest Research institute in Boulder, Colorado. Including launch costs, PUNCH is being funded for no more than $165 million.

    TRACERS

    The second mission is Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites, or TRACERS.

    NASA TRACER mission


    NASA TRACER MIssion

    The TRACERS investigation was partially selected as a NASA-launched rideshare mission, meaning it will be launched as a secondary payload with PUNCH. NASA’s Science Mission Directorate is emphasizing secondary payload missions as a way to obtain greater science return. TRACERS will observe particles and fields at the Earth’s northern magnetic cusp region – the region encircling Earth’s pole, where our planet’s magnetic field lines curve down toward Earth. Here, the field lines guide particles from the boundary between Earth’s magnetic field and interplanetary space down into the atmosphere.

    In the cusp area, with its easy access to our boundary with interplanetary space, TRACERS will study how magnetic fields around Earth interact with those from the Sun. In a process known as magnetic reconnection, the field lines explosively reconfigure, sending particles out at speeds that can approach the speed of light. Some of these particles will be guided by the Earth’s field into the region where TRACERS can observe them.

    Magnetic reconnection drives energetic events all over the universe, including coronal mass ejections and solar flares on the Sun. It also allows particles from the solar wind to push into near-Earth space, driving space weather there. TRACERS will be the first space mission to explore this process in the cusp with two spacecraft, providing observations of how processes change over both space and time. The cusp vantage point also permits simultaneous observations of reconnection throughout near-Earth space. Thus, it can provide important context for NASA’s Magnetospheric Multiscale mission, which gathers detailed, high-speed observations as it flies through single reconnection events at a time.

    TRACERS’ unique measurements will help with NASA’s mission to safeguard our technology and astronauts in space. The mission is led by Craig Kletzing at the University of Iowa in Iowa City. Not including rideshare costs, TRACERS is funded for no more than $115 million.

    Launch date for the two missions is no later than August 2022. Both programs will be managed by the Explorers Program Office at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The Explorers Program, the oldest continuous NASA program, is designed to provide frequent, low-cost access to space using principal investigator-led space science investigations relevant to the work of NASA’s Science Mission Directorate in astrophysics and heliophysics. The program is managed by Goddard for the Science Mission Directorate, which conducts a wide variety of research and scientific exploration programs for Earth studies, space weather, the solar system and universe.

    For additional information, and the chance to ask more about the missions, please join us for a Reddit Ask Me Anything at 12:30 – 1:30 p.m. EDT June 21.

    For more information about the Explorers Program, visit:

    https://explorers.gsfc.nasa.gov

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 8:45 am on June 4, 2019 Permalink | Reply
    Tags: "A Twisted Tale of Sunspots", , , Solar research   

    From Medium: “A Twisted Tale of Sunspots” 

    From Medium

    May 28. 2019
    James Maynard

    One of the greatest questions in solar astronomy may have an answer after more than 400 years, thanks to an inquisitive team of German researchers. Every eleven years, the population of sunspots seen on the surface of our local star reaches a maximum, before dying out. Another population of sunspots then begin to appear (this time with their poles reversed from the previous cycle) before they too peak and fade away. This process may be well-known, but the reason for these 11-year peaks has remained a mystery, until now.

    The magnetic field of the Sun may be affected by the gravitational forces of Venus, Earth, and Jupiter, resulting in the cyclical sunspot cycle, a new study suggests. Researchers compared solar cycles to the positions of planets, finding the gravitational forces of these three worlds acts like a cosmic clock, regulating the solar cycle.

    “There is an astonishingly high level of concordance: what we see is complete parallelism with the planets over the course of 90 cycles. Everything points to a clocked process,” explained Frank Stefani of the German-based research institute Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

    1
    The sunspot cycle can be easily seen in this graphic, produced by NASA in 2017. We are currently at a low point in the cycle. Image credit: NASA/ARC/Hathaway

    You Missed a Spot Right There

    Sunspots were first clearly seen between the years 1610 and 1611, in the years following the invention of the telescope. Although Galileo is often given credit for the discovery, several pioneering astronomers of the era reported finding the distinctive dark spots on the Moon around the same time.

    2
    A sunspot, seen by the Solar Dynamics Observatory (SDO) shows off it’s powerful magnetic field. Image credit: NASA’s Goddard Space Flight Center/SDO

    NASA/SDO

    The publication of the first paper recognizing these features, by Dutch astronomer Johannes Fabricius, shocked the zeitgeist of early 17th Century society, which always held a belief in a perfect, unchanging, featureless Sun.

    3
    De Maculis in Sole observatis et Apparente earum cum Sole Conversione Narratio (Narration on Spots Observed on the Sun and their Apparent Rotation with the Sun), published in June 1611, was the first scientific paper published describing sunspots. Public domain image.

    Everybody Line up!

    The greatest gravitational force of planets on the Sun occurs once every 11.07 years, when Venus, Earth, and Jupiter come into alignment. Gravitational pull from this arrangement results in tidal forces on the Sun, similar to the way our own Moon draws oceans upward, creating tides.

    This effect is not strong enough to affect the interior of our stellar companion, so the timing of this alignment was previously overlooked in earlier studies of sunspot cycles. However, a physical effect known as the Tayler instability is capable of altering the behavior of conductive liquids or a plasma.

    The Tayler instability alters the rate of flow of material (the flux) in an object, like the Sun, and can affect magnetic fields. This effect can be triggered by relatively small movements in materials like the plasma found at the surface of the Sun. Due to this effect, these relatively minor tidal forces can alter the relationship of sunspots to their direction of travel. This measurement, known as the helicity of a region of plasma, alters the solar dynamo (the physical process which generates the magnetic field of our parent star).

    “Magnetic fields are a little like rubber bands. They consist of continuous loops of lines of force that have both tension and pressure. Like rubber bands, magnetic fields can be strengthened by stretching them, twisting them, and folding them back on themselves. This stretching, twisting, and folding is done by the fluid flows within the Sun,” The Marshall Space Flight Center explains.


    A video explaining the process resulting in the formation of sunspots. Credit: NASA Goddard

    Stefani had his doubts whether or not tidal forces from the planets could alter an event as powerful as the solar dynamo. However, once he realized the Tayler instability could provide the trigger for the process, Stefani and his team began developing a computer simulation to model the process.

    “I asked myself: What would happen if the plasma was impacted on by a small, tidal-like perturbation? The result was phenomenal. The oscillation was really excited and became synchronized with the timing of the external perturbation,” Stefani explains.

    Sun, Spot, Sun!

    The motion of the sun is complex, with multiple effects contributing to its intricate dance. As the sun rotates, the equator moves faster than the material near the poles. In a process known as the omega effect, lines of the sun’s magnetic field are pulled and stretched near the equator, creating a bend in the direction of the solar equator.

    A little-understood alpha effect then affects the magnetic lines, pushing them toward their original alignment, resulting in a twisting of the lines of force.

    3
    Magnetic lines can be seen above sunspots in this image of charged particles, captured in extreme ultraviolet light. Image credit: NASA/GSFC/Solar Dynamics Observatory.

    These actions create the cool, dark areas we know as sunspots. While most of the surface of the Sun glows around 5,500 degrees Celsius (9,900 Fahrenheit), sunspots remain at a relatively cool 3,200 Celsius (5,800 Fahrenheit). Sunspots are still fairly bright, only appearing dark against the torrid backdrop of the solar surface.

    This new model, folding tidal forces into the complex processes of the solar dynamo, could explain several questions astronomers and physicists have about the solar dynamo, and how it affects our parent star.

    The Parker Solar Probe is currently in orbit around the Sun, in a mission to study our stellar companion up close.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    This program could answer a multitude of mysteries concerning Sun over the next few years.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    About Medium

    Medium is an online publishing platform developed by Evan Williams, and launched in August 2012. It is owned by A Medium Corporation. The platform is an example of social journalism, having a hybrid collection of amateur and professional people and publications, or exclusive blogs or publishers on Medium, and is regularly regarded as a blog host.

    Williams developed Medium as a way to publish writings and documents longer than Twitter’s 140-character (now 280-character) maximum.

     
  • richardmitnick 5:23 pm on April 17, 2019 Permalink | Reply
    Tags: "Exploring Filaments on the Sun", , , , , , Solar research   

    From AAS NOVA: “Exploring Filaments on the Sun” 

    AASNOVA

    From AAS NOVA

    17 April 2019
    Susanna Kohler

    1
    This image of the Sun’s chromosphere reveals dark cuts across its surface: solar filaments. A new study explores how these filaments are built. [NOAA/SEL/USAF]

    Images of the Sun’s chromosphere often reveal dark threads cutting across the Sun’s face. New research has now explored how these solar filaments are built from magnetic fields and plasma.

    Two-Faced Structures

    3
    A solar eruptive prominence as seen in extreme UV light on March 30, 2010, with Earth superimposed for a sense of scale. [NASA/SDO]

    NASA/SDO

    Solar filaments may look like deep cracks in the Sun’s façade, but in reality, they are enormous arcs of hot plasma that extend above the Sun’s surface. Because this plasma is slightly cooler than the solar surface below, they appear dark against the hotter background.

    Unfamiliar with filaments? You’ve likely seen plenty of them in images — but from a different angle! Filaments are the same structures as solar prominences, the loops of plasma we can see suspended above the Sun’s limbs. When prominences appear on the side of the Sun facing us, they take the form of filaments from our point of view.

    Shaped by Fields

    Filaments are often associated with various forms of solar activity. They last for days, frequently hanging above active regions of the Sun; filament channels are often the origin of eruptions from the Sun’s surface. To better understand our active and energetic Sun, understanding the structures of filaments is an important step.

    Unfortunately, this is challenging! We know that filament structure is largely due to the magnetic fields — whose forces suspend the filaments against the downward pull of gravity — but we don’t have the ability to directly measure the magnetic field in the Sun’s atmosphere. A team of scientists at the University of Science and Technology of China has instead taken an indirect approach: they explored filaments by looking at the motion of plasma along them.

    4
    Top: time-distance map characterizing the oscillations at one position on the filament spine. Bottom: a Doppler map, averaged over time, that shows the rotation around the spine of the filament. Blue indicates motion toward the observer, red away. [Adapted from Awasthi et al. 2019]

    A Double Decker?

    Scientists Arun Awasthi, Rui Liu, and Yuming Wang examined observations of a filament that appeared near active region AR 12685 in October 2017, captured with the 1-m New Vacuum Solar Telescope in China. The team used these high-resolution images to explore bulk motions of plasma in the filament.

    Awasthi and collaborators found that the filament displayed two different types of motion: rotation around its central spine, and longitudinal oscillations along its spine. The longitudinal oscillations in the eastern segment of the filament were distinct from those in the west, suggesting that the magnetic field lines underneath these two segments have different lengths and curvatures.

    On the whole, the motions observed in the filament indicate that magnetic structure for filaments is complicated. The authors argue that more than one model is likely at work; they propose a “double-decker” picture for the filament in which a flux rope (a twisted bundle of magnetic field lines) sits on top of a sheared arcade (a series of distorted loops).

    Awasthi and collaborators conclude with specific predictions of indicators we can look for in future filament observations to test this model. If correct, this view of filament structure brings us a little closer to understanding the complex magnetic fields that control solar activity.

    Citation

    “Double-decker Filament Configuration Revealed by Mass Motions,” Arun Kumar Awasthi et al 2019 ApJ 872 109.
    https://iopscience.iop.org/article/10.3847/1538-4357/aafdad/meta

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 3:47 pm on April 5, 2019 Permalink | Reply
    Tags: "And the Blobs Just Keep on Coming", , , Solar research, Two German-NASA Helios spacecraft which launched in 1974 and 1976 to study the Sun   

    From NASA Goddard Space Flight Center: “And the Blobs Just Keep on Coming” 

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    April 4, 2019

    Lina Tran
    lina.tran@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    When Simone Di Matteo first saw the patterns in his data, it seemed too good to be true. “It’s too perfect!” Di Matteo, a space physics Ph.D. student at the University of L’Aquila in Italy, recalled thinking. “It can’t be real.” And it wasn’t, he’d soon find out.

    Di Matteo was looking for long trains of massive blobs — like a lava lamp’s otherworldly bubbles, but anywhere from 50 to 500 times the size of Earth — in the solar wind. The solar wind, whose origins aren’t yet fully understood, is the stream of charged particles that blows constantly from the Sun. Earth’s magnetic field, called the magnetosphere, shields our planet from the brunt of its radiation. But when giant blobs of solar wind collide with the magnetosphere, they can trigger disturbances there that interfere with satellites and everyday communications signals.

    In his search, Di Matteo was re-examining archival data from the two German-NASA Helios spacecraft, which launched in 1974 and 1976 to study the Sun.

    NASA/DLR Helios spacecraft

    1
    Engineers inspect the Helios 2 spacecraft.
    Credits: NASA’s Goddard Space Flight Center

    But this was 45-year-old data he’d never worked with before. The flawless, wave-like patterns he initially found hinted that something was leading him astray.

    It wasn’t until uncovering and removing those false patterns that Di Matteo found exactly what he was looking for: dotted trails of blobs that oozed from the Sun every 90 minutes or so. The scientists published their findings in JGR Space Physics on Feb. 21, 2019. They think the blobs could shed light on the solar wind’s beginnings. Whatever process sends the solar wind out from the Sun must leave signatures on the blobs themselves.

    Making Way for New Science

    Di Matteo’s research was the start of a project NASA scientists undertook in anticipation of the first data from NASA’s Parker Solar Probe mission, which launched in 2018.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    Over the next seven years, Parker will fly through unexplored territory, soaring as close as 4 million miles from the Sun. Before Parker, the Helios 2 satellite held the record for the closest approach to the Sun at 27 million miles, and scientists thought it might give them an idea of what to expect. “When a mission like Parker is going to see things no one has seen before, just a hint of what could be observed is really helpful,” Di Matteo said.

    The problem with studying the solar wind from Earth is distance. In the time it takes the solar wind to race across the 93 million miles between us and the Sun, important clues to the wind’s origins — like temperature and density — fade. “You’re constantly asking yourself, ‘How much of what I’m seeing here is because of evolution over four days in transit, and how much came straight from the Sun?’” said solar scientist Nicholeen Viall, who advised Di Matteo during his research at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Helios data — some of which was collected at just one-third the distance between the Sun and Earth — could help them begin to answer these questions.

    Modeling Blobs

    The first step was tracing Helios’ measurements of the blobs to their source on the Sun. “You can look at spacecraft data all you want, but if you can connect it back to where it came from on the Sun, it tells a more complete story,” said Samantha Wallace, one of the study collaborators and a physics Ph.D. student at the University of New Mexico in Albuquerque.

    Wallace used an advanced solar wind model to link magnetic maps of the solar surface to Helios’ observations, a tricky task since computer languages and data conventions have changed greatly since Helios’ days. Now, the researchers could see what sorts of regions on the Sun were likely to bud into blobs of solar wind.


    In the days before Parker Solar Probe, the record-breaking spacecraft for speed and closest approach to the Sun were the two Helios probes, launched in the mid-1970s. This visualization shows the orbits of Helios 1 and Helios 2, from an oblique view above the ecliptic plane.
    Credits: Tom Bridgman/NASA’s Scientific Visualization Studio

    Sifting the Evidence

    Then, Di Matteo searched the data for specific wave patterns. They expected conditions to alternate — hot and dense, then cold and tenuous — as individual blobs engulfed the spacecraft and moved on, in a long line.

    The picture-perfect patterns Di Matteo first found worried him. “That was a red flag,” Viall said. “The actual solar wind doesn’t have such precise, clean periodicities. Usually when you get such a precise frequency, it means some instrument effect is going on.” Maybe there was some element of the instrument design they weren’t considering, and it was imparting effects that had to be separated from true solar wind patterns.

    Di Matteo needed more information on the Helios instruments. But most researchers who worked on the mission have long since retired. He did what anyone else would do, and turned to the internet.

    Many Google searches and a weekend of online translators later, Di Matteo unearthed a German instruction manual that describes the instruments dedicated to the mission’s solar wind experiment. Decades ago, when Helios was merely a blueprint and before anyone ever launched a spacecraft to the Sun, scientists didn’t know how best to measure the solar wind. To prepare themselves for different scenarios, Di Matteo learned, they equipped the probes with two different instruments that would each measure certain solar wind properties in their own way. This was the culprit responsible for Di Matteo’s perfect waves: the spacecraft itself, as it alternated between two instruments.

    After they removed segments of data taken during routine instrument-switching, the researchers looked again for the blobs. This time, they found them. The team describes five instances that Helios happened to catch trains of blobs. While scientists have spotted these blobs from Earth before, this is the first time they’ve studied them this close to the Sun, and with this level of detail. They outline the first conclusive evidence that the blobs are hotter and denser than the typical solar wind.

    The Return of the Blobs

    Whether blob trains bubble in 90-minute intervals continuously or in spurts, and how much they vary between themselves, is still a mystery. “This is one of those studies that brought up more questions than we answered, but that’s perfect for Parker Solar Probe,” Viall said.

    Parker Solar Probe aims to study the Sun up close, seeking answers to basic questions about the solar wind. “This is going to be very helpful,” said Aleida Higginson, the mission’s deputy project scientist at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “If you want to even begin to understand things you’ve never seen before, you need to know what we’ve measured before and have a solid scientific interpretation for it.”

    Parker Solar Probe performs its second solar flyby on April 4, which brings it 15 million miles from the Sun — already cutting Helios 2’s record distance in half. The researchers are eager to see if blobs show up in Parker’s observations. Eventually, the spacecraft will get so close it could catch blobs right after they’ve formed, fresh out of the Sun.

    See the full article here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 3:00 pm on April 5, 2019 Permalink | Reply
    Tags: , , , Coronal rain, , Emily Mason, Helmet streamers, , , , Solar research,   

    From NASA Goddard Space Flight Center: Women in STEM “Unexpected Rain on Sun Links Two Solar Mysteries” Emily Mason 

    NASA Goddard Banner
    From NASA Goddard Space Flight Center

    April 5, 2019

    Miles Hatfield
    miles.s.hatfield@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    For five months in mid 2017, Emily Mason did the same thing every day. Arriving to her office at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, she sat at her desk, opened up her computer, and stared at images of the Sun — all day, every day. “I probably looked through three or five years’ worth of data,” Mason estimated. Then, in October 2017, she stopped. She realized she had been looking at the wrong thing all along.

    Mason, a graduate student at The Catholic University of America in Washington, D.C., was searching for coronal rain: giant globs of plasma, or electrified gas, that drip from the Sun’s outer atmosphere back to its surface. But she expected to find it in helmet streamers, the million-mile tall magnetic loops — named for their resemblance to a knight’s pointy helmet — that can be seen protruding from the Sun during a solar eclipse. Computer simulations predicted the coronal rain could be found there. Observations of the solar wind, the gas escaping from the Sun and out into space, hinted that the rain might be happening. And if she could just find it, the underlying rain-making physics would have major implications for the 70-year-old mystery of why the Sun’s outer atmosphere, known as the corona, is so much hotter than its surface. But after nearly half a year of searching, Mason just couldn’t find it. “It was a lot of looking,” Mason said, “for something that never ultimately happened.”

    1
    Mason searched for coronal rain in helmet streamers like the one that appears on the left side of this image, taken during the 1994 eclipse as viewed from South America. A smaller pseudostreamer appears on the western limb (right side of image). Named for their resemblance to a knight’s pointy helmet, helmet streamers extend far into the Sun’s faint corona and are most readily seen when the light from the Sun’s bright surface is occluded. Credits: © 1994 Úpice observatory and Vojtech Rušin, © 2007 Miloslav Druckmüller

    The problem, it turned out, wasn’t what she was looking for, but where. In a paper published today in The Astrophysical Journal Letters, Mason and her coauthors describe the first observations of coronal rain in a smaller, previously overlooked kind of magnetic loop on the Sun. After a long, winding search in the wrong direction, the findings forge a new link between the anomalous heating of the corona and the source of the slow solar wind — two of the biggest mysteries facing solar science today.

    How It Rains on the Sun

    Observed through the high-resolution telescopes mounted on NASA’s SDO spacecraft, the Sun – a hot ball of plasma, teeming with magnetic field lines traced by giant, fiery loops — seems to have few physical similarities with Earth.

    NASA/SDO

    But our home planet provides a few useful guides in parsing the Sun’s chaotic tumult: among them, rain.

    On Earth, rain is just one part of the larger water cycle, an endless tug-of-war between the push of heat and pull of gravity. It begins when liquid water, pooled on the planet’s surface in oceans, lakes, or streams, is heated by the Sun. Some of it evaporates and rises into the atmosphere, where it cools and condenses into clouds. Eventually, those clouds become heavy enough that gravity’s pull becomes irresistible and the water falls back to Earth as rain, before the process starts anew.

    On the Sun, Mason said, coronal rain works similarly, “but instead of 60-degree water you’re dealing with a million-degree plasma.” Plasma, an electrically-charged gas, doesn’t pool like water, but instead traces the magnetic loops that emerge from the Sun’s surface like a rollercoaster on tracks.

    2
    Coronal rain, like that shown in this movie from NASA’s SDO in 2012, is sometimes observed after solar eruptions, when the intense heating associated with a solar flare abruptly cuts off after the eruption and the remaining plasma cools and falls back to the solar surface. Mason was searching for coronal rain not associated with eruptions, but instead caused by a cyclical process of heating and cooling similar to the water cycle on Earth.
    Credits: NASA’s Solar Dynamics Observatory/Scientific Visualization Studio/Tom Bridgman, Lead Animator

    At the loop’s foot points, where it attaches to the Sun’s surface, the plasma is superheated from a few thousand to over 1.8 million degrees Fahrenheit. It then expands up the loop and gathers at its peak, far from the heat source. As the plasma cools, it condenses and gravity lures it down the loop’s legs as coronal rain.

    Mason was looking for coronal rain in helmet streamers, but her motivation for looking there had more to do with this underlying heating and cooling cycle than the rain itself. Since at least the mid-1990s, scientists have known that helmet streamers are one source of the slow solar wind, a comparatively slow, dense stream of gas that escapes the Sun separately from its fast-moving counterpart. But measurements of the slow solar wind gas revealed that it had once been heated to an extreme degree before cooling and escaping the Sun. The cyclical process of heating and cooling behind coronal rain, if it was happening inside the helmet streamers, would be one piece of the puzzle.

    The other reason connects to the coronal heating problem — the mystery of how and why the Sun’s outer atmosphere is some 300 times hotter than its surface. Strikingly, simulations have shown that coronal rain only forms when heat is applied to the very bottom of the loop. “If a loop has coronal rain on it, that means that the bottom 10% of it, or less, is where coronal heating is happening,” said Mason. Raining loops provide a measuring rod, a cutoff point to determine where the corona gets heated. Starting their search in the largest loops they could find — giant helmet streamers — seemed like a modest goal, and one that would maximize their chances of success.

    She had the best data for the job: Images taken by NASA’s Solar Dynamics Observatory, or SDO, a spacecraft that has photographed the Sun every twelve seconds since its launch in 2010. But nearly half a year into the search, Mason still hadn’t observed a single drop of rain in a helmet streamer. She had, however, noticed a slew of tiny magnetic structures, ones she wasn’t familiar with. “They were really bright and they kept drawing my eye,” said Mason. “When I finally took a look at them, sure enough they had tens of hours of rain at a time.”

    At first, Mason was so focused on her helmet streamer quest that she made nothing of the observations. “She came to group meeting and said, ‘I never found it — I see it all the time in these other structures, but they’re not helmet streamers,’” said Nicholeen Viall, a solar scientist at Goddard, and a coauthor of the paper. “And I said, ‘Wait…hold on. Where do you see it? I don’t think anybody’s ever seen that before!’”

    A Measuring Rod for Heating

    These structures differed from helmet streamers in several ways. But the most striking thing about them was their size.

    “These loops were much smaller than what we were looking for,” said Spiro Antiochos, who is also a solar physicist at Goddard and a coauthor of the paper. “So that tells you that the heating of the corona is much more localized than we were thinking.”

    3
    Mason’s article analyzed three observations of Raining Null-Point Topologies, or RNTPs, a previously overlooked magnetic structure shown here in two wavelengths of extreme ultraviolet light. The coronal rain observed in these comparatively small magnetic loops suggests that the corona may be heated within a far more restricted region than previously expected. Credits: NASA’s Solar Dynamics Observatory/Emily Mason

    While the findings don’t say exactly how the corona is heated, “they do push down the floor of where coronal heating could happen,” said Mason. She had found raining loops that were some 30,000 miles high, a mere two percent the height of some of the helmet streamers she was originally looking for. And the rain condenses the region where the key coronal heating can be happening. “We still don’t know exactly what’s heating the corona, but we know it has to happen in this layer,” said Mason.

    A New Source for the Slow Solar Wind

    But one part of the observations didn’t jibe with previous theories. According to the current understanding, coronal rain only forms on closed loops, where the plasma can gather and cool without any means of escape. But as Mason sifted through the data, she found cases where rain was forming on open magnetic field lines. Anchored to the Sun at only one end, the other end of these open field lines fed out into space, and plasma there could escape into the solar wind. To explain the anomaly, Mason and the team developed an alternative explanation — one that connected rain on these tiny magnetic structures to the origins of the slow solar wind.

    In the new explanation, the raining plasma begins its journey on a closed loop, but switches — through a process known as magnetic reconnection — to an open one. The phenomenon happens frequently on the Sun, when a closed loop bumps into an open field line and the system rewires itself. Suddenly, the superheated plasma on the closed loop finds itself on an open field line, like a train that has switched tracks. Some of that plasma will rapidly expand, cool down, and fall back to the Sun as coronal rain. But other parts of it will escape – forming, they suspect, one part of the slow solar wind.

    Mason is currently working on a computer simulation of the new explanation, but she also hopes that soon-to-come observational evidence may confirm it. Now that Parker Solar Probe, launched in 2018, is traveling closer to the Sun than any spacecraft before it, it can fly through bursts of slow solar wind that can be traced back to the Sun — potentially, to one of Mason’s coronal rain events.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    After observing coronal rain on an open field line, the outgoing plasma, escaping to the solar wind, would normally be lost to posterity. But no longer. “Potentially we can make that connection with Parker Solar Probe and say, that was it,” said Viall.

    Digging Through the Data

    As for finding coronal rain in helmet streamers? The search continues. The simulations are clear: the rain should be there. “Maybe it’s so small you can’t see it?” said Antiochos. “We really don’t know.”

    But then again, if Mason had found what she was looking for she might not have made the discovery — or have spent all that time learning the ins and outs of solar data.

    “It sounds like a slog, but honestly it’s my favorite thing,” said Mason. “I mean that’s why we built something that takes that many images of the Sun: So we can look at them and figure it out.”

    Related:

    IRIS Spots Plasma Rain on Sun’s Surface

    NASA IRIS spacecraft, a spacecraft that takes spectra in three passbands, allowing us to probe different layers of the solar atmosphere


    And the Blobs Just Keep on Coming

    See the full article here.


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

    Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.


    NASA/Goddard Campus

     
  • richardmitnick 12:22 pm on April 1, 2019 Permalink | Reply
    Tags: "Solar Orbiter during thermal-vacuum tests", , , , , , Solar research   

    From European Space Agency: “Solar Orbiter during thermal-vacuum tests” 

    ESA Space For Europe Banner

    From European Space Agency

    01/04/2019

    ESA/NASA Solar Orbiter depiction

    1

    An infrared view of our Solar Orbiter spacecraft, which is currently undergoing a series of tests at the IABG facility in Ottobrunn, Germany, ahead of its launch, scheduled for February 2020.

    Selected in 2011 as the first medium-class mission in ESA’s Cosmic Vision programme, Solar Orbiter was designed to perform unprecedented close-up observations of the Sun. The spacecraft carries a suite of 10 state-of-the-art instruments to observe the turbulent, sometimes violent, surface of the Sun and study the changes that take place in the solar wind that flows outward at high speed from our nearest star.

    Solar Orbiter’s unique orbit will allow scientists to study our parent star and its corona in much more detail than previously possible, and to observe specific features for longer periods than can ever be reached by any spacecraft circling the Earth. In addition, it will measure the solar wind close to the Sun, in an almost pristine state, and provide high-resolution images of the uncharted polar regions of the Sun.

    After the preliminary definition and design phase, the mission started its integration and qualification in 2016, including environmental testing of the spacecraft as well as validation of all mission systems and sub-systems.

    The first phase of Solar Orbiter’s environmental testing campaign was conducted in IABG’s special thermal-vacuum chamber in December 2018. Inside the chamber, powerful lamps are used to produce a ‘solar beam’ that simulates the Sun’s radiation to demonstrate that the spacecraft can sustain the extreme temperatures it will encounter in the Sun’s vicinity.

    This picture was taken with an infrared camera, and the colouring indicates the temperatures of the spacecraft surface, corresponding to the range indicated in the colour bar on the right-hand side. During this thermal-vacuum test on the spacecraft, the solar beam was used at its maximum flux of about 1800 W/m2, reaching temperatures up to 107,6 ºC. An additional thermal-vacuum test was conducted on the heat shield that protects the entire platform from direct solar radiation: during this test, which used infrared plates to simulate the Sun’s heat, the heat shield reached higher temperatures, up to 520 ºC, similar to what it will experience during operations.

    In this view, the spacecraft panel that will face the Sun is visible on the left, covered with the heat shield. The dark elements visible in the upper part of the panel are sliding doors that will open the path for sunlight to reach the remote-sensing instruments during science operations. Some of the thrusters that will be used to control the spacecraft orbit and to perform manoeuvres are hosted on the panel that is visible on the right in this view.

    A video showing the spacecraft rotating as part of a simulated orbit-control-manoeuvre is available here.

    After completing the thermal-vacuum tests, Solar Orbiter also successfully concluded the mechanical testing phase, including intense vibration tests, shaking the spacecraft to ensure that it will survive the stress of launch.

    More information: Good vibes for Solar Orbiter

    Solar Orbiter is an ESA-led mission with strong NASA participation. It will be launched from Cape Canaveral aboard a NASA-supplied Atlas V launch vehicle.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 10:25 am on March 23, 2019 Permalink | Reply
    Tags: , , , , , Solar Flares Waves Jets and Ejections, Solar research   

    From AAS NOVA: “Flares, Waves, Jets, and Ejections” 

    AASNOVA

    From AAS NOVA

    22 March 2019
    Susanna Kohler

    1
    Solar Dynamics Observatory images at 171 Å of a blowout jet erupting in the solar corona on 9 Mar 2011. The dashed white line shows the direction of jet eruption. [SDO/Miao et al. 2018]

    NASA/SDO

    Our Sun often exhibits a roiling surface full of activity. But how do the different types of eruptions and disturbances we see relate to one another? Observations of one explosive jet are helping us to piece together the puzzle.

    Looking for Connections

    2
    A coronal blowout jet captured by the Solar Dynamics Observatory on 9 Mar 2011. [Miao et al. 2018]

    Energy travels through and from the Sun via dozens of different phenomena. We see ultraviolet waves that propagate across the disk, loops and flares of plasma stretching into space, enormous coronal mass ejections that expel material through the solar system, and jets of all different sizes extending from the Sun’s surface and atmospheric layers. A longstanding mission for solar physicists has been to relate these phenomena into a broader picture explaining how energy is released from our closest star.

    3
    Positions of the two STEREO satellites relative to the Sun and the Earth. SDO orbits the Earth. The green arrow shows the eruption direction of the blowout jet. [Miao et al. 2018]

    An Enlightening Explosion

    On 9 March 2011, a coronal blowout jet erupted from the Sun’s surface. Three spacecraft were on hand to watch: the Solar Dynamics Observatory, STEREO Ahead, and STEREO Behind.

    NASA/STEREO spacecraft

    These observatories were each located roughly 90° from each other, providing a view of the Sun’s surface from multiple angles at the moment of the explosion.

    What did they these observatories see?

    The flare
    The eruption of the blowout jet — which lasted ~21 minutes — was accompanied by a class 9.4 solar flare.
    The wave
    Shortly after the jet launch, an arc-shaped extreme ultraviolet (EUV) wave appeared on the southeastern side of the jet. This wave lasted ~4 minutes and propagated away from the site of the jet.
    The jet
    The jet itself contains both bright and dark material. The dark material appears to be due to a mini-filament — a thread of cool, dense gas suspended above the Sun’s surface by magnetic fields — that erupted in the jet base.
    The coronal mass ejection
    The two STEREO spacecraft captured what happened on large scales in the outer corona of the Sun, revealing an explosive coronal mass ejection spewing matter into space. The ejection consisted of two structures: a jet-like component and a bubble-like component.

    Causal Ties?

    4
    STEREO Ahead (left) and Behind (right) images of the coronal mass ejection in the outer corona. Both a jet-like and a bubble-like component can be seen. [Miao et al. 2018]

    These observations provide an unprecedented look at multiple types of solar activity all occurring simultaneously — and they suggest causal ties between the different phenomena.

    In particular, the authors propose a relation in which the EUV wave was a fast-mode magnetohydrodynamic wave driven by the blowout jet eruption. They also suggest that the jet-like component of the coronal mass ejection is the outer-corona extension of the hot part of the blowout jet body, while the bubble-like component might be associated with the eruption of the mini-filament at the jet base.

    More observations like those of this event are needed to draw definitive conclusions, but this explosion has provided some definite clues about the relationship between different phenomena as the Sun lashes out into its surroundings.

    Bonus

    Watch the propagation of the EUV wave (top video), the eruption of the blowout jet (middle video), and the coronal mass ejections (bottom video) in the clips below. Videos can not be
    Copied and presented here. You can view them at the full article.

    Citation

    “A Blowout Jet Associated with One Obvious Extreme-ultraviolet Wave and One Complicated Coronal Mass Ejection Event,” Y. Miao et al 2018 ApJ 869 39.
    https://iopscience.iop.org/article/10.3847/1538-4357/aaeac1/meta

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 9:32 am on March 8, 2019 Permalink | Reply
    Tags: , , , Bernhard Kliem of the University of Potsdam in Germany and his colleagues scrutinized a CME recorded on May 13 2013 by NASA’s Solar Dynamics Observatory, But it was unclear how coronal mass ejections or CMEs get started, , , , Over about half an hour the blobs shot upward and merged into a large flux rope which briefly arced over the solar surface before erupting into space., , Solar plasma eruptions are the sum of many parts a new look at a 2013 coronal mass ejection shows, Solar research, Solar scientists have long wondered what drives big bursts of plasma called coronal mass ejections. New analysis of an old eruption suggests the driving force might be merging magnetic blobs, That quick growth supports the idea that CMEs grow through magnetic reconnection, That speedy setup might make it more difficult to predict when CMEs are about to occur, The team led by Tingyu Gou and Rui Liu of the University of Science and Technology of China in Hefei, They found that before it erupted a vertical sheet of plasma split into blobs marking breaking and merging magnetic field lines   

    From Science News: “Merging magnetic blobs fuel the sun’s huge plasma eruptions” 

    From Science News

    March 7, 2019
    Lisa Grossman

    Before coronal mass ejections, plasma shoots up, breaks apart and then comes together again.

    1
    BURSTING WITH PLASMA Solar scientists have long wondered what drives big bursts of plasma called coronal mass ejections. New analysis of an old eruption suggests the driving force might be merging magnetic blobs.

    Solar plasma eruptions are the sum of many parts, a new look at a 2013 coronal mass ejection shows.

    These bright, energetic bursts happen when loops of magnetism in the sun’s wispy atmosphere, or corona, suddenly snap and send plasma and charged particles hurtling through space (SN Online: 8/16/17).

    But it was unclear how coronal mass ejections, or CMEs, get started. One theory suggests that a twisted tube of magnetic field lines called a flux rope hangs out on the solar surface for hours or days before a sudden perturbation sends it expanding off the solar surface.

    Another idea is that the sun’s magnetic field lines are forced so close together that the lines break and recombine with each other. The energy of that magnetic reconnection forms a short-lived flux rope that quickly erupts.

    “We do not know which comes first,” the flux rope or the reconnection, says solar physicist Bernhard Kliem of the University of Potsdam in Germany.

    Kliem and his colleagues scrutinized a CME recorded on May 13, 2013, by NASA’s Solar Dynamics Observatory.

    NASA/SDO

    They found that before it erupted, a vertical sheet of plasma split into blobs, marking breaking and merging magnetic field lines. Over about half an hour, the blobs shot upward and merged into a large flux rope, which briefly arced over the solar surface before erupting into space. That quick growth supports the idea that CMEs grow through magnetic reconnection, the team, led by Tingyu Gou and Rui Liu of the University of Science and Technology of China in Hefei, reports March 6 in Science Advances.

    “This was actually surprising, that this reconnection was rather fast,” Kliem says. That speedy setup might make it more difficult to predict when CMEs are about to occur. That’s too bad because, when aimed at Earth, these bursts cause auroras and can knock out power grids and damage satellites.


    A STAR’S CME IS BORN The sun’s coronal mass ejections seem to result from many small plasma blobs combining. In this video, enhanced data from NASA’s Solar Dynamics Observatory shows a vertical sheet of plasma suddenly break into blobs at about 17 seconds. Shortly after, the blobs rearrange themselves into a loop, and the loop bursts off the sun’s surface. At 30 seconds, more distant observations from the SOHO telescope show the CME’s progress. (A second, unrelated CME erupts off the right side of the sun near the video’s end.)

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 9:04 am on March 7, 2019 Permalink | Reply
    Tags: , , , , , , , Solar research   

    From COSMOS Magazine: “Mechanics of coronal mass ejections revealed” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    07 March 2019
    Lauren Fuge

    1
    A coronal mass ejection captured by NASA’s Solar Dynamics Observatory in September, 2017. NASA/SDO.

    NASA/SDO

    An international team of astronomers has untangled new insight into the birth of coronal mass ejections, the most massive and destructive explosions from the sun.

    In a paper published in the journal Science Advances, a team led by Tingyu Gou from the University of Science and Technology of China was able to clearly observe the onset and evolution of a major solar eruption for the first time.

    From a distance the sun seems benevolent and life-giving, but on closer inspection it is seething with powerful fury. Its outer layer – the corona – is a hot and wildly energetic place that constantly sends out streams of charged particles in great gusts of solar wind.

    It also emits localised flashes known as flares, as well as enormous explosions of billions of tons of magnetised plasma called coronal mass ejections (CMEs).

    These eruptions could potentially have a big effect on Earth. CMEs can damage satellite electronics, kill astronauts on space walks, and cause magnetic storms that can disrupt electricity grids.

    Studying CMEs is key to improving the capability to forecast them, and yet, for decades, their origin and evolution have remained elusive.

    “The underlying physics is a disruption of the coronal magnetic field,” explains Bernhard Kliem, co-author on the paper, from the University of Potsdam in Germany.

    Such a disruption allows an expanding bubble of plasma – a CME – to build up, driving it and the magnetic field upwards. The “bubble” can tear off and erupt, often accompanied by solar flares.

    The magnetic field lines then fall back and combine with neighbouring lines to form a less-stressed field, creating the beautiful loops seen in many UV and X-ray images of the sun.

    “This breaking and re-closing process is called magnetic reconnection, and it is of great interest in plasma physics, astrophysics, and space physics,” says Kliem.

    NASA Magnetic reconnection, Credit: M. Aschwanden et al. (LMSAL), TRACE, NASA

    NASA TRACE spacecraft (1998-2010)

    But the reason why the coronal magnetic field is disturbed at all is a matter of continuing debate.

    “To many, an instability of the magnetic field is the primary reason,” says Kliem. “This requires the magnetic field to form a twisted flux tube, known as magnetic flux rope, where the energy to be released in the eruption can be stored.”

    The theory holds that turbulence causes the magnetic flux ropes to become tangled and unstable, and if they suddenly rearrange themselves in the process of magnetic reconnection, they can release the trapped energy and trigger a CME.

    Others in the field think that it’s the other way around – magnetic reconnection is the trigger that forms the flux rope in the first place.

    It’s a tricky question to tease out because flux ropes and reconnection are so intertwined. Recent studies [Nature] even suggest that there’s another layer of complexity: smaller magnetic loops called mini flux ropes, or plasmoids, which continuously form in a fractal-like fashion and may have a cascading influence on bigger events like a CME.

    To get a better handle on this complex process, the team observed the evolution of a CME that erupted on May 13, 2013. By combining multi-wavelength data from NASA’s Solar Dynamics Observatory (SDO) with modern analysis techniques, they were able to determine the correct sequence of events: that a magnetic reconnection in the solar corona formed the flux rope, which then became unstable and erupted.

    Specifically, they found that the CME bubble continuously evolved from mini flux ropes, bridging the gap between micro- and macro-scale dynamics and thus illuminating a complete evolutionary path of CMEs.

    The next step, Kliem says, is to understand another important phenomenon in the eruption process: a thin, elongated structure known as a “current sheet”, in which the mini flux ropes were formed.

    “We need to study when and where the coronal magnetic field forms such current sheets that can build up a flux rope, which then, in turn, can erupt to drive a solar eruption,” he concludes.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

     
  • richardmitnick 3:57 pm on March 1, 2019 Permalink | Reply
    Tags: "Solving a Stellar Abundance Problem (with a Little Help from Our Oceans)", , Solar research   

    From AAS NOVA: “Solving a Stellar Abundance Problem (with a Little Help from Our Oceans)” 

    AASNOVA

    From AAS NOVA

    1 March 2019
    Kerry Hensley

    1
    What do stellar plasma and saltwater have in common? More than you might think. [NASA/SDO (left) and NOAA (right)]

    NASA/SDO

    When solving mysteries about distant astronomical objects, sometimes it pays to take inspiration from sources closer to home. In today’s example, strange fluid behavior in the Earth’s oceans — combined with a healthy helping of magnetic fields — may provide the answer to a long-standing puzzle about the changing composition of red-giant stars.

    2
    Simulated salt fingers in fluids with decreasing Rayleigh numbers. The Rayleigh number determines whether heat in a system is transferred primarily through diffusion or convection. [Fariarehman]

    A Possibility for Instability

    Red giants undergo a process called dredge-up, during which their outer convective envelopes bring fusion products up to the surface, altering the chemical abundances there. After the dredge-up, surface abundances aren’t expected to change — yet observations show that they continue to evolve long after the dredge-up is complete. What drives this unexpected late-stage mixing in red giants?

    One solution involves an instability called fingering convection. Fingering convection occurs in fluids with vertical gradients in temperature and chemical composition — a setup we see everywhere from the interiors of stars to Earth’s oceans. When the equilibrium of such a fluid is perturbed, the temperature diffuses more quickly than the chemical composition as the system seeks to reestablish equilibrium, triggering a runaway effect.

    What does this look like in practice? Take the ocean as an example. The density of saltwater is determined by temperature and salt content, and warm saltwater often lies atop denser, colder water that is less salty. When a bubble of warmer water is pushed into the colder water beneath it, it cools quickly, but the salt is slow to diffuse outward. The cold, salty water is now denser than the water surrounding it, causing it to sink deeper. As this process continues, salt-rich “fingers” dive downward, eventually depositing the saltier water deep in the ocean.

    The density of the material in stellar interiors depends on temperature, which diffuses rapidly, and chemical composition, which diffuses slowly — the perfect setup for fingering convection.

    3
    Vertical velocity of fluid parcels for three values of the Lorentz force coefficient, HB, which increases as the square of the magnetic field strength. [Harrington & Garaud 2019]

    Peter Harrington and Pascale Garaud (University of California, Santa Cruz) used numerical models to explore the effect of magnetic fields on the rate of convection in stellar interiors.

    In their simulations, the authors apply a vertical background magnetic field of varying strength and randomly impose small perturbations in the temperature and composition. The perturbations grow as the instability takes hold, forming narrow fingers aligned with the magnetic field.

    4
    Evolution of the compositional Nusselt number (a measure of the strength of the vertical compositional transport) over time. Simulations with higher magnetic field strengths saturate more rapidly and reach higher rates of vertical transport. [Harrington & Garaud 2019]

    Implications for Convection

    The authors find that including magnetic fields in their simulations increases the rate of convection, with stronger magnetic fields leading to more rapid convection. For a purely vertical magnetic field of 0.03 Tesla (reasonable for stellar interiors), the convection rate increases by two orders of magnitude — enough to resolve the disagreement between theory and observations.

    Magnetized fingering convection should affect more than just red giants; the authors note that main-sequence stars and white dwarfs should also exhibit this behavior, which needs to be accounted for when interpreting observed surface abundances.

    Citation

    “Enhanced Mixing in Magnetized Fingering Convection, and Implications for Red Giant Branch Stars,” Peter Z. Harrington & Pascale Garaud 2019 ApJL 870 L5.
    https://iopscience.iop.org/article/10.3847/2041-8213/aaf812/meta

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
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