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  • richardmitnick 11:03 am on November 9, 2017 Permalink | Reply
    Tags: , , , , Cloudy with a chance of coronal mass ejections, , , Sun studies   

    From astrobites: “Cloudy with a chance of coronal mass ejections” 

    Astrobites bloc


    Nov 9, 2017
    Kerrin Hensley

    Title: Using the Coronal Evolution to Successfully Forward Model CMEs’ In Situ Magnetic Profiles
    Authors: Christina Kay and Nat Gopalswamy
    First Author’s Institution: NASA Goddard Space Flight Center

    Status: Accepted to the Journal of Geophysical Research – Space Physics, open access

    Coronal Mass Ejections and You

    An eruption on April 16, 2012 was captured here by NASA’s Solar Dynamics Observatory in the 304 Angstrom wavelength, which is typically colored in red. Credit: NASA/SDO/AIA


    Coronal mass ejections (CMEs) are immense eruptions of solar plasma and magnetic fields. When a CME strikes a planet, it can have huge effects; over billions of years, CMEs can strip away a planet’s atmosphere. In the short term, CMEs wreak havoc at Earth by causing dangerous and costly geomagnetic storms.

    In 1859, a CME impacted the Earth and caused the most intense geomagnetic storm ever recorded, resulting in stunning auroral displays over much of the northern hemisphere (Figure 1) and widespread failure of telegraph systems. An event of this magnitude today would cause huge damage to power grids, satellites, and oil pipelines—resulting in a trillion dollars of damage in the United States alone. So, how can we prevent this from occurring?

    Enter the growing field of space weather forecasting. Although we can’t stop the Sun from ejecting CMEs, we can try to figure out if a given CME will hit the Earth, and how severe the resulting geomagnetic storm will be if it does. The severity of a geomagnetic storm is linked to the CME’s magnetic field conditions, especially the magnitude of the southward-pointing magnetic field (i.e. the component of the magnetic field that opposes the Earth’s magnetic field at the equator). If the CME’s properties can be accurately estimated, the severity of the resulting geomagnetic storm can be estimated too, allowing for power grids and satellites to be put into safe mode if necessary.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 9:12 am on November 9, 2017 Permalink | Reply
    Tags: , , , , , Carrying Energy to the Corona with Waves, , DKIST under construction by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui Hawaii USA at an altitude of 3084 m (10118 ft) with a planned completion date of 201, , Sun studies   

    From AAS NOVA: “Carrying Energy to the Corona with Waves” 



    8 November 2017
    Susanna Kohler

    How does the solar corona, the Sun’s outer atmosphere visible in this image, get so hot? [Luc Viatour]

    The solar corona has a problem: it’s weirdly hot! A new study explores how magnetic waves might solve the mystery of the unusually hot corona by transporting energy to the outer atmosphere of the Sun.

    The Problem with the Corona

    The temperatures of different layers of the Sun. [ISAS/JAXA]

    The corona, the outer layer of the Sun’s atmosphere, has typical temperatures of 1–3 million K — significantly hotter than the cool 5,800 K of the photosphere, the surface of the Sun far below it. Since temperatures ordinarily drop the further you get from the heat source (in this case, the Sun’s atom-fusing center), this so-called “coronal heating problem” poses a definite puzzle.

    As is the case for many astronomical mysteries, the answer may have something to do with magnetic fields. Alfvén waves, magnetohydrodynamic waves that travel through magnetized plasma, could potentially carry energy from the convective zone beneath the Sun’s photosphere up into the solar atmosphere. There, the Alfvén waves could turn into shock waves that dissipate their energy as heat, causing the increased temperature of the corona.

    Daniel K. Inouye Solar Telescope, DKIST under construction by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui, Hawaii, USA, at an altitude of 3,084 m (10,118 ft), with a planned completion date of 2018

    Predicting Observations

    Alfvén waves as a means of delivering heat to the corona makes for a nice picture, but there’s a lot of work to be done before we can be certain that this is the correct model. Observational evidence of Alfvén waves has thus far been limited to specific conditions — and the observations have not yet been enough to convince us that Alfvén waves can deliver enough energy to explain the corona’s temperature.

    Lucas Tarr, a scientist at the Naval Research Laboratory, argues that upcoming solar telescopes may make it easier to detect these waves — but first we need to know what to look for! In a recent study, Tarr uses a simplified analytic model to show which frequencies of waves are likely to carry power when magnetic field lines in the corona are pertubed.

    The power carried by Alfvén waves as a function of frequency, as a result of an initial perturbation, plotted for several different initial conditions (such as the size of the perturbation or the length of the loop on which it is introduced). [Tarr 2017]

    A Promising Future

    Tarr modeled the effects of a minor perturbation — like a local magnetic reconnection event in the corona — on a coronal arcade, a common structure of magnetic field loops found in the corona. Tarr determined that such a disturbance would peak in power at a low frequency (maybe tens of millihertz, or oscillations on scales of minutes), but a substantial portion of the power is carried by waves of higher frequencies (0.5–4 Hz, or oscillations on scales of seconds).

    Tarr’s findings confirm that with the cadence and sensitivity of current instrumentation, we would not expect to be able to detect these Alfvén waves. The results do indicate, however, that high-cadence observations with future telescope technology — like the instrumentation at the upcoming Daniel K. Inouye Solar Telescope, which should be completed in 2018 — may have the ability to reveal the presence of these waves and confirm the model of Alfvén waves as the means by which the Sun achieves its mysteriously hot corona.

    Lucas A. Tarr 2017 ApJ 847 1. doi:10.3847/1538-4357/aa880a

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    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 4:19 pm on July 26, 2017 Permalink | Reply
    Tags: , , , , , Dynamo, More slowly rotating stars have a magnetic cycle that repeats more quickly, Sun studies, The Secret of Magnetic Cycles in Stars, The solar cycle, The Sun’s magnetic field flips approximately every 11 years   

    From CfA: “The Secret of Magnetic Cycles in Stars” 

    Harvard Smithsonian Center for Astrophysics

    Center For Astrophysics

    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279

    This combination of images and artist’s impression shows changes in the Sun’s appearance and magnetic fields during part of the solar cycle. The Sun’s magnetic field flips approximately every 11 years, defining this cycle. The switch happens around at the maximum peak of magnetic activity, when sunspot and flare activity reaches its peak. We show images of the Sun captured by NASA’s Solar Dynamics Observatory (SDO) obtained on 10th October 2010 (solar minimum), 25th December 2013 (solar maximum) and on 25th June 2017 (solar minimum), combined with artist’s impressions to show the magnetic field of the Sun. Images: NASA/SDO/A. Strugarek et al; Illustrations: L. Almeida, Federal University of Rio Grande do Norte (UFRN), Brazil.


    Using new numerical simulations and observations, scientists may now be able to explain why the Sun’s magnetic field reverses every eleven years. This significant discovery explains how the duration of the magnetic cycle of a star depends on its rotation, and may help us understand violent space weather phenomena around the Sun and similar stars.

    During what is known as the solar cycle, the magnetic field of the Sun has reversed every 11 years over the past centuries. This flip, where the south magnetic pole switches to north and vice versa, occurs during the peak of each solar cycle and originates from a process called a “dynamo”. Magnetic fields are generated by a dynamo, which involves the rotation of the star as well as convection and the rising and falling of hot gas in the star’s interior.

    For the Sun, scientists know that magnetic fields originate in its turbulent outer layers and have a complex dependency upon how quickly the Sun is rotating. Scientists have also measured magnetic cycles for distant stars with fundamental properties similar to those of the Sun. By studying the characteristics of these magnetic properties, scientists have a very promising way to better understand the magnetic evolution in our Sun associated with the dynamo process.

    An international collaboration that includes the University of Montréal, the Harvard-Smithsonian Center for Astrophysics, the Commissariat à l’énergie atomique et aux énergies alternatives and the Universidade Federal do Rio Grande do Norte, carried out a set of 3D simulations of the interiors of stars similar to the Sun to explain the origin of their magnetic field cycles. The scientists found that the period of the magnetic cycle depends on the rotation rate of a star. The trend is that more slowly rotating stars have a magnetic cycle that repeats more quickly.

    “The trend we found differs from theories developed in the past. This really opens new research avenues for our understanding of the magnetism of stars,” said Antoine Strugarek of the Commissariat à l’énergie atomique et aux énergies alternatives, France, the lead author of a paper published in the July 14th issue of Science Magazine.

    An important advance is that the scientists’ model can explain the cycle of both the Sun and stars that astronomers categorize as Sun-like. Previously scientists thought that the Sun’s cycle might differ in behavior from those of Sun-like stars, with a shorter magnetic cycle than expected.

    “Our work supports the idea that our Sun is an average, middle-aged yellow dwarf star, with a magnetic cycle compatible with cycles from its stellar cousins,” said co-author Jose-Dias Do Nascimento of the Harvard-Smithsonian Center for Astrophysics (CfA) and the University of Rio G. do Norte (UFRN), Brazil. “In other words we confirm that the Sun really is a useful proxy for understanding other stars in many ways.”

    By observing more and more stars and exploring stellar structures different from those of the Sun with numerical simulations, the team of researchers hopes to refine their new scenario for the origin of stellar magnetic cycles.

    One long-term goal of this work is to gain a better understanding of “space weather”, a term used to describe the wind of particles that blows away from the Sun and other stars. The acceleration mechanism for this wind is likely related to magnetic fields in the atmospheres of stars. In extreme cases, space weather can interrupt electrical power on Earth, and it can be very dangerous to satellites and astronauts.

    “The changes throughout a magnetic cycle have effects throughout the Solar System and other planetary systems thanks to the influence of space weather,” said Do Nascimento.

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

  • richardmitnick 7:45 am on July 18, 2017 Permalink | Reply
    Tags: , , , , , Science backing for formation-flying Sun-watcher Proba-3, Sun studies   

    From ESA: “Science backing for formation-flying Sun-watcher Proba-3” 

    ESA Space For Europe Banner

    European Space Agency

    17 July 2017
    No writer credit

    Proba-3, ESA’s amazing testbed
    Released 30/03/2013 3:10 pm
    Copyright ESA-P. Carril

    ESA’s Science Programme has agreed to support the technology-demonstrating Proba-3, a double-satellite formation-flying mission tasked with observing a region of the Sun normally hidden from view.

    Set for launch in late 2020, the two satellites making up Proba-3 will fly at a precise separation to cast a shadow across space, blocking out the disc of the Sun to reveal details of its ghostly surrounding ‘corona’ – usually masked by dazzling sunlight.

    Proba-3, like all the missions in the Proba series, is first and foremost a technology demonstrator, exploring precision formation-flying techniques so that future multiple satellites flying together could perform equivalent tasks to a single giant spacecraft.

    But, following a longstanding Proba tradition, the mission has also been given an ambitious scientific goal: returning scientifically useful data is a good way of proving the technology works as planned.

    Proba-3 satellites form artificial eclipse
    Released 12/09/2016. Copyright ESA.

    Proba-3 will offer solar scientists a window on the inner segment of the solar corona – a mysterious region because it is more than a million degrees hotter than the surface of the Sun it surrounds.

    Up until now, the best way to observe the corona has been during a solar eclipse, although stray light through Earth’s atmosphere is a limiting factor.

    As an alternative, space-flown ‘coronagraphs’ create artificial eclipses inside Sun-watching satellites such as SOHO and Stereo, but stray light still bends around their blocking discs, limiting access to the all-important inner corona.


    NASA/STEREO spacecraft

    Proba-3 will get around this by flying the disc of its coronagraph on a separate satellite, exactly 150 m apart, lined up with the Sun. This should open up a new view of dynamic regions extremely close to the solar surface, where the solar wind and the eruptions called ‘coronal mass ejections’ are born. Coronal mass ejections are primary sources of disturbed space weather at the Earth.

    Solar eclipses. Released 12/06/2008. Copyright Wendy Carlos & Fred Espenak.

    Proba-3 is funded through ESA’s Directorate of Technology, Engineering and Quality, but in June the Agency’s Science Programme Committee endorsed the mission for additional backing through the Directorate of Science.

    “It was clear that it would be very beneficial to have this mission supported in the Science programme,” explains Andrei Zhukov of the Royal Observatory of Belgium, serving as Principal Investigator for Proba’s coronagraph.

    “There was widespread enthusiasm in the solar physics community. The Science Programme Committee is advised in turn by its advisory committees composed of scientists from all around Europe, giving independent endorsements, and they recommended Proba-3 be supported as a ‘mission of opportunity’.

    “In plain terms, the running of Proba-3’s Science Operations Centre, which will process and distribute scientific data to scientists across Europe will be funded by the Science programme. This centre will be hosted here in Belgium, with contributions to the data processing pipeline made by Germany, Poland and Romania.

    A fiery solar explosion. Released 16/09/2013. Copyright SOHO (ESA/NASA)/S. Hill.
    A coronal mass ejection observed by the ESA/NASA SOHO space mission on 4 January 2002 has been coloured to indicate the intensity of the matter being ejected by the Sun. White represents the greatest intensity, red/orange somewhat less, and blue the least.

    An extreme-ultraviolet image of the Sun captured by SOHO’s EIT (Extreme ultraviolet Imaging Telescope) instrument is superimposed on the image. The shaded blue disc surrounding the Sun at the centre is a mask in SOHO’s LASCO instrument that blots out direct sunlight to allow study of the details in the Sun’s corona.

    “During each highly elliptical 19.6 hour orbit, Proba-3 will be imaging the corona for about six hours at a time, at a typical rate of one image per minute, although we have the ability to increase this rate to once every two seconds for phenomena of special interest.

    “So we will be returning lots of unique data, increasing scientific knowledge of the Sun and its surrounding corona.”

    Proba-3 project development continues to progress well, with a structural and thermal model version of the coronagraph built, ahead of its critical design review due to take place this autumn, followed by that of the entire mission.

    The challenge is in keeping the satellites safely controlled and correctly positioned relative to each other. This will be accomplished using various new technologies, including bespoke formation-flying software, GPS information, intersatellite links, startrackers, optical visual sensors and optical metrologies for close-up manoeuvring.

    Published on Mar 23, 2015
    Dancing is probably the oldest human artform – and now ESA’s Proba-3 precision formation-flying mission intends to extend the art of dance to space.
    Like dancers, a pair of minisatellites will move around each other, their relative positions maintained to millimetre-scale precision, as if they were both parts of one giant spacecraft.
    Their mission is to cast a shadow from one minisatellite onto another, in order to form an artificial total solar eclipse in space – then study the fine details of the Sun’s wispy atmosphere, the solar corona.
    Franco Ongaro, ESA Director of Technical and Quality Management; Frederic Teston, Head of System and Cost Engineering; Andrea Santovincenzo, ESA engineer and the project’s manager Agnes Mestreau-Garreau, explain how to go about teaching a space mission to dance. Credit: European Space Agency, ESA.

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    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.

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  • richardmitnick 9:24 am on March 20, 2017 Permalink | Reply
    Tags: , , , , Equinox, Lunar Eclipse, , NASA Satellites Ready When Stars and Planets Align, , Solstice, Sun studies, Transits   

    From Goddard: “NASA Satellites Ready When Stars and Planets Align” A NASA Tour de Force 

    NASA Goddard Banner
    NASA Goddard Space Flight Center

    March 17, 2017
    Mara Johnson-Groh
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    No image caption. No image credit

    The movements of the stars and the planets have almost no impact on life on Earth, but a few times per year, the alignment of celestial bodies has a visible effect. One of these geometric events — the spring equinox — is just around the corner, and another major alignment — a total solar eclipse — will be visible across America on Aug. 21, with a fleet of NASA satellites viewing it from space and providing images of the event.

    To understand the basics of celestial alignments, here is information on equinoxes, solstices, full moons, eclipses and transits:


    Earth spins on a tilted axis. As our planet orbits around the sun, that tilt means that during half of the year, the Northern Hemisphere receives more daylight — its summertime — and during the other half of the year, the Southern Hemisphere does. Twice a year, Earth is in just the right place so that it’s lined up with respect to the sun, and both hemispheres of the planet receive the same amount of daylight. On these days, there are almost equal amounts of day and night, which is where the word equinox — meaning “equal night” in Latin — comes from. The equinox marks the onset of spring with a transition from shorter to longer days for half the planet, along with more direct sunlight as the sun rises higher above the horizon. In 2017, in the Northern Hemisphere, the spring equinox occurs on March 20. Six months later, fall begins with the autumnal equinox on Sept. 22.

    During the equinoxes, both hemispheres receive equal amounts of daylight. Image not to scale. Credits: NASA’s Goddard Space Flight Center/Genna Duberstein


    As Earth continues along in its orbit after the equinox, it eventually reaches a point where its tilt is at the greatest angle to the plane of its orbit — and the point where one half of the planet is receiving the most daylight and the other the least. This point is the solstice — meaning “sun stands still” in Latin — and it occurs twice a year. These days are our longest and shortest days, and mark the change of seasons to summer and winter.

    During the solstices, Earth reaches a point where its tilt is at the greatest angle to the plane of its orbit, causing one hemisphere to receive more daylight than the other. Image not to scale.
    Credits: NASA’s Goddard Space Flight Center/Genna Duberstein

    Full Moon and New Moon

    As Earth goes around the sun, the moon is also going around Earth. There is a point each month when the three bodies align with Earth between the sun and the moon. During this phase, viewers on Earth can see the full face of the moon reflecting light from the sun — a full moon. The time between full moons is about four weeks — 29.5 days to be exact. Halfway between full moons, the order of the three bodies reverses and the moon lies between the sun and Earth. During this time, we can’t see the moon reflecting the sun’s light, so it appears dark. This is the new moon.

    When the moon’s orbit around Earth lines up on the same plane as Earth’s orbit around the sun, its shadow is cast across the planet. Image not to scale. Credits: NASA’s Goddard Space Flight Center/Genna Duberstein

    Lunar Eclipse

    Sometimes, during a full moon, Earth lines up perfectly between the moon and the sun, so its shadow is cast on the moon. From Earth’s viewpoint, we see a lunar eclipse. The plane of the moon’s orbit around Earth isn’t precisely aligned with the plane of the Earth’s orbit around the sun so on most months we don’t see an eclipse. The next lunar eclipse — which will be visible throughout much of Asia, Europe, Africa and Australia — will occur on Aug. 7.

    When the moon falls completely in Earth’s shadow, a total lunar eclipse occurs. Only light travelling through Earth’s atmosphere, which is bent into the planet’s shadow, is reflected off
    the moon, giving it a reddish hue. Image not to scale. Credits: NASA’s Goddard Space Flight Center/Genna Duberstein

    Solar Eclipse

    A solar eclipse happens when the moon blocks our view of the sun. This can only happen at a new moon, when the moon’s orbit positions it between the sun and Earth — but this doesn’t happen every month. As mentioned above, the plane of the moon’s orbit around Earth isn’t precisely aligned with the plane of the Earth’s orbit around the sun so, from Earth’s view, on most months we see the moon passing above or below the sun. A solar eclipse happens only on those new moons where the alignment of all three bodies are in a perfectly straight line.

    When the moon blocks all of the sun’s light, a total eclipse occurs, but when the moon is farther away — making it appear smaller from our vantage point on Earth — it blocks most, but not all of the sun. This is called an annular eclipse, which leaves a ring of the sun’s light still visible from around the moon. This alignment usually occurs every year or two, but is only visible from a small area on Earth.

    On Aug. 21, a total solar eclipse will move across America. While lunar eclipses are visible from entire hemispheres of Earth, a total solar eclipse is visible only from a narrow band along Earth’s surface. Since this eclipse will take about an hour and a half to cross an entire continent, it is particularly important scientifically, as it allows observations from many places for an extended duration of time. NASA has funded 11 projects to take advantage of the 2017 eclipse and study its effects on Earth as well as study the sun’s atmosphere.

    When the moon’s orbit around Earth lines up on the same plane as Earth’s orbit around the sun, its shadow is cast across the planet. Image not to scale. Credits: NASA’s Goddard Space Flight Center/Genna Duberstein


    Planet transit. NASA/Ames

    An eclipse is really just a special kind of transit — which is when any celestial body passes in front of another. From Earth we are able to watch transits such as Mercury and Venus passing in front of the sun. But such transits also offer a way to spot new distant worlds. When a planet in another star system passes in front of its host star, it blocks some of the star’s light — making it appear slightly dimmer. By watching for changes in the amount of light over time, we can deduce the presence of a planet. This method has been used to discover thousands of planets, including the TRAPPIST-1 planets.

    The seven planets that orbit the Trappist-1 star, in order of their distance from the star, compared to Earth’s solar system. https://www.thestar.com/news/world/2017/02/22/what-to-know-about-the-newly-discovered-trappist-1-solar-system.html

    During a transit, a planet passes in between us and the star it orbits. This method is commonly used to find new exoplanets in our galaxy. Image not to scale.
    Credits: NASA’s Goddard Space Flight Center/Genna Duberstein

    For more information about how NASA looks at these events, visit:


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    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.

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  • richardmitnick 2:09 pm on September 9, 2016 Permalink | Reply
    Tags: , , , , Sun studies   

    From Eos: “Scientists Get First Glimpse of Solar Wind as It Forms” 

    Eos news bloc


    JoAnna Wendel

    An extreme ultraviolet light image of the Sun and its corona from NASA’s Solar Terrestrial Relations Observatory (STEREO). Credit: NASA/STEREO

    NASA/STEREO spacecraft
    NASA/STEREO spacecraft

    What does solar wind look like when it first forms from the Sun’s corona? Now, with new satellite images manipulated to remove background light, scientists can answer that question.

    “This is part of the last major connection we need to make to understand how [the Sun] influences the environment around the Earth,” Craig DeForest, an astrophysicist at the Southwest Research Institute in Boulder, Colo., told Eos. DeForest is the lead author on a new paper describing the novel technique, published last week in the Astrophysical Journal.

    A Tricky Search

    Back in the 1960s, scientists discovered the solar wind, a constant flow from the Sun of extremely high temperature plasma that’s so hot the Sun’s gravity can’t hold it. Scientists knew that the solar wind was somehow connected to the Sun’s corona—the bright layer of the Sun’s atmosphere that can be seen during a solar eclipse—but until now, scientists weren’t sure how one transitioned into the other.

    This transition is important because “we’re trying to understand, among other things, why the solar wind near the Earth is variable and gusty,” DeForest said. This gustiness can affect things like the trajectory of coronal mass ejections—huge magnetic explosions from that Sun that, when they hit Earth, can knock out telecommunications, short out satellite circuitry, and damage electrical transmission lines.

    But studying the transition between the corona and the solar wind is difficult—the solar wind is very faint against a background full of stars and interplanetary dust, DeForest said, making it hard to discern exactly what is happening as the solar wind gets created.

    When scientists looked at previous images and “saw the [corona] fade, it was difficult to tell whether it was fading in an absolute sense or dropping below stellar background,” DeForest continued.

    Unfixing the View

    With computer-processed images from NASA’s Solar Terrestrial Relations Observatory (STEREO), the scientists finally observed this transition. The processing removed objects of “fixed brightness,” DeForest said, like the dust cloud that fills the inner solar system and the background stars themselves. That left the moving and variable features of the solar wind itself.

    Two views of the solar wind: STEREO’s images (left) before computer processing and (right) after processing. Scientists used an algorithm to dim the light coming from the background star field. Credit: NASA/STEREO, data from Craig DeForest, SwRI

    Scientists already knew that masses of particles in the corona are controlled by magnetic fields, which gives the Sun its “rays”—similar to those in a child’s drawing, DeForest said. The new images revealed the farthest reaches of the magnetically controlled corona, showing that once the material travels about a third of the distance from the Sun to the Earth, the magnetic fields weaken enough that solar wind particles can disperse from the field lines and fan out more like an Earthly wind.

    The video below, from NASA, compares this transformation of the solar wind from rays to dispersed particles to the way water shoots from a water gun or hose: Closer to the water gun, the water is one mass, but as it moves farther from the gun, it disperses into a spray of individual droplets.

    Investigating this transition region will help scientists to predict the arrival and strength of the Sun’s outbursts— Earth-bound coronal mass ejections—after they pass through a full astronomical unit of the existing solar wind, DeForest said.

    See the full article here .

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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 5:08 am on July 28, 2016 Permalink | Reply
    Tags: , , Magnetic Field Of Sun and Its Kin, , Sun studies   

    From Chandra: “Astronomers Gain New Insight into Magnetic Field Of Sun and Its Kin” 

    NASA Chandra Banner

    NASA Chandra Telescope

    NASA Chandra

    July 27, 2016
    Molly Porter
    Marshall Space Flight Center, Huntsville, Ala.

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.


    An artist’s illustration depicts the interior of a low-mass star, such as GJ 3253, a low-mass red dwarf star about 31 light years away from Earth, seen in an X-ray image from Chandra in the inset.
    Credits: X-ray: NASA/CXC/Keele Univ./N. Wright et al; Optical: DSS

    Astronomers have used data from NASA’s Chandra X-ray Observatory to make a discovery that may have profound implications for understanding how the magnetic field in the Sun and stars like it are generated.

    Researchers have discovered that four old red dwarf stars with masses less than half that of the Sun are emitting X-rays at a much lower rate than expected.

    A new study of four low-mass stars may have important implications for understanding the magnetic field of the Sun.

    Magnetic fields are responsible for solar storms that can generate auroras, knock out satellites, and affect astronauts in space.

    X-ray emission is an excellent indicator of a star’s magnetic field strength.

    Two low-mass stars observed with Chandra and two by ROSAT showed their X-ray emission was similar to that of stars like the Sun.

    NASA/ROSAT satellite
    DLR/NASA ROSAT satellite

    X-ray emission is an excellent indicator of a star’s magnetic field strength so this discovery suggests that these stars have much weaker magnetic fields than previously thought.

    Since young stars of all masses have very high levels of X-ray emission and magnetic field strength, this suggests that the magnetic fields of these stars weakened over time. While this is a commonly observed property of stars like our Sun, it was not expected to occur for low-mass stars, as their internal structure is very different.

    The Sun and other stars are giant spheres of superheated gas. The Sun’s magnetic field is responsible for producing sunspots, its 11-year cycle, and powerful eruptions of particles from the solar surface. These solar storms can produce spectacular auroras on Earth, damage electrical power systems, knock out communications satellites, and affect astronauts in space.

    “We have known for decades that the magnetic field on the Sun and other stars plays a huge role in how they behave, but many details remain mysterious,” said lead author Nicholas Wright of Keele University in the United Kingdom. “Our result is one step in the quest to fully understand the Sun and other stars.”

    The rotation of a star and the flow of gas in its interior both play a role in producing its magnetic field. The rotation of the Sun and similar stars varies with latitude (the poles versus the equator) as well as in depth below the surface. Another factor in the generation of magnetic field is convection. Similar to the circulation of warm air inside an oven, the process of convection in a star distributes heat from the interior of the star to its surface in a circulating pattern of rising cells of hot gas and descending cooler gas.

    Convection occurs in the outer third (by radius) of the Sun, while the hot gas closer to the core remains relatively still. There is a difference in the speed of rotation between these two regions. Many astronomers think this difference is responsible for generating most of the magnetic field in the Sun by causing magnetic fields along the border between the convection zone and the core to wind up and strengthen. Since stars rotate more slowly as they age, this also plays a role in how the magnetic field of such stars weakens with time

    “In some ways you can think of the inside of a star as an incredibly complicated dance with many, many dancers,” said co-author Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Some dancers move with each other while others move independently. This motion generates magnetic field, but how it works in detail is extremely challenging to determine.”

    For stars much less massive than the Sun, convection occurs all the way into the core of the star. This means the boundary between regions with and without convection, thought to be crucial for generating magnetic field in the Sun, does not exist. One school of thought has been that magnetic field is generated mostly by convection in such stars. Since convection does not change as a star ages, their magnetic fields would not weaken much over time.

    By studying four of these low-mass red dwarf stars in X-rays, Wright and Drake were able to test this hypothesis. They used NASA’s Chandra X-ray Observatory to study two of the stars and data from the ROSAT satellite to look at two others.

    “We found that these smaller stars have magnetic fields that decrease as they age, exactly as it does in stars like our Sun,” said Wright. “This really goes against what we would have expected.”

    These results imply that the interaction along the convection zone-core boundary does not dominate the generation of magnetic field in stars like our Sun, since the low mass stars studied by Wright and Drake lack such a region and yet their magnetic properties are very similar.

    A paper describing these results by Wright and Drake appears in the July 28th issue of the journal Nature. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

    Read More from NASA’s Chandra X-ray Observatory.

    For more Chandra images, multimedia and related materials, visit:


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    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

  • richardmitnick 11:21 am on March 18, 2016 Permalink | Reply
    Tags: , , Sun studies,   

    From NAOJ Universe of Spectroscopy: “Spectra of the Solar Corona” 



    Universe of Spectroscopy
    Universe of Spectroscopy

    To observe the corona surrounding the Sun, we have to wait for an opportunity to view a total solar eclipse when the Moon fully blocks the solar disk. In visible light, the bright solar surface hampers observation of the faint corona.

    Observations at shorter wavelength light such as ultraviolet and X-ray are appropriate to investigate the corona in detail. The high-temperature corona emits more radiation at shorter wavelength. However, ultraviolet and X-ray radiation cannot penetrate the Earth’s atmosphere. That is the reason why we need a space observatory.

    The observational satellite Hinode’s onboard instrument, called Extreme-ultraviolet Imaging Spectrometer (EIS), was designed for obtaining spectra of the solar corona. The extreme-ultraviolet is a wavelength range of the shorter wavelength region of ultraviolet radiation. We can find many spectral lines radiating from high temperature (higher than one million Kelvin) plasma.

    JAXA HINODE spacecraft
    JAXA HINODE spacecraft

    The extreme-ultraviolet is a wavelength range of the shorter wavelength region of ultraviolet radiation. We can find many spectral lines radiating from high temperature (higher than one million Kelvin) plasma.

    The most frequent lines are emission lines originating in ionized iron. Iron, with the symbol Fe, is atomic number 26 and will have 26 electrons. In such a hot corona, a part of the electrons is removed from iron atoms, and more electrons are removed at higher temperature. Analysis of the emission lines of the ionized iron yields information on the temperature of the corona.

    A part of the extreme-ultraviolet spectrum obtained by the EIS installed on Hinode. Many emission lines caused by ionized iron are visible. For example, “Fe X” means an iron ion removed nine electrons from a neutral iron atom. Combining ratios between other iron charge states yields the temperature of the corona. In addition, analyzing the wavelength shift of emission lines, we will derive the corona’s motion velocity.

    Is the corona’s temperature one million Kelvin?

    It is generally believed that the corona’s temperature is one million Kelvin. However, plasma of various temperatures is distributed throughout the corona. “Warm” plasma has a temperature of about one million Kelvin, while “hot” plasma is higher than two million Kelvin. Moreover, super hot plasma with a temperature of higher than ten million Kelvin is observed when a giant solar flare erupts. Studying the solar spectra at extreme-ultraviolet is essential to developing an understanding of the temperature distribution and the dynamics of the solar corona that has such a diversity of temperatures.

    The solar corona’s image in the extreme-ultraviolet emission line of an ionized iron. The typical temperature of each iron charge state is indicated.

    See the full article here .

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    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior

    ALMA Array

    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

  • richardmitnick 4:32 pm on November 21, 2015 Permalink | Reply
    Tags: , , , Sun studies   

    From Astronomy Now: “A research milestone in helping predict solar flares” 

    Astronomy Now bloc

    Astronomy Now

    17 November 2015

    Left: An image of our Sun taken by NASA’s Solar Dynamics Observatory, showing million-degree plasma being channelled into loop-like shapes by the immense magnetic fields. Right: A zoom-in of the highly magnetic region of the Sun’s corona studied by Dr. David Jess and colleagues from Queen’s University Belfast, Northern Ireland. Image credit: Queen’s University Belfast.

    Solar flares are massive explosions of energy in the Sun’s atmosphere. Experts have warned that even a single ‘monster’ solar flare could cause up to $2 trillion worth of damage on Earth, including the loss of satellites and electricity grids, as well the potential knock-on dangers to human life and health. A key goal of the $300 million Daniel K Inouye Solar Telescope (DKIST), which will be the largest solar telescope in the world when construction is finished in 2019 on the Pacific island of Maui, is the measurement of magnetic fields in the outer regions of the Sun’s atmosphere.

    DKIST telescope

    The technique pioneered by the Queen’s-led team, just published in the journal Nature Physics, will feed into the DKIST project, as well as allowing greater advance warning of potentially devastating space storms. The new technique allows changes in the Sun’s magnetic fields, which drive the initiation of solar flares, to be monitored up to ten times faster than previous methods.

    The Queen’s-led team, which spans academics from universities in Europe, the Asia-Pacific and the USA, harnessed data from both NASA’s premier space-based telescope (the Solar Dynamics Observatory), and the ROSA multi-camera system, which was designed at Queen’s University Belfast, using detectors made by Northern Ireland company Andor Technology.

    Lead researcher Dr David Jess from Queen’s Astrophysics Research Centre said: “Continual outbursts from our Sun, in the form of solar flares and associated space weather, represent the potentially destructive nature of our nearest star. Our new techniques demonstrate a novel way of probing the Sun’s outermost magnetic fields, providing scientists worldwide with a new approach to examine, and ultimately understand, the precursors responsible for destructive space weather.

    “Queen’s is increasingly becoming a major player on the astrophysics global stage. This work highlights the strong international links we have with other leading academic institutes from around the world, and provides yet another example of how Queen’s research is at the forefront of scientific discovery.”

    See the full article here .

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  • richardmitnick 1:58 pm on November 18, 2015 Permalink | Reply
    Tags: , , , , , , Sun studies   

    From AAS NOVA: “Eruptions from the Sun” 


    Amercan Astronomical Society

    18 November 2015
    Susanna Kohler

    An image captured of the Sun by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly, a few hours after a coronal mass ejection erupted off of the Sun’s northwest limb. [NASA/SDO/AIA]

    Gif of a movie of the CME, taken by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly at a wavelength of 304Å. The original movie can be found in [cited] the article.

    The Sun often exhibits outbursts, launching material from its surface in powerful releases of energy. Recent analysis of such an outburst — captured on video by several Sun-monitoring spacecraft — may help us understand the mechanisms that launch these eruptions.

    Many Outbursts

    Solar jets are elongated, transient structures that are thought to regularly release magnetic energy from the Sun, contributing to coronal heating and solar wind acceleration. Coronal mass ejections (CMEs), on the other hand, are enormous blob-like explosions, violently ejecting energy and mass from the Sun at incredible speeds.

    But could these two types of events actually be related? According to a team of scientists at the University of Science and Technology of China, they may well be. The team, led by Jiajia Liu, has analyzed observations of a coronal jet that they believe prompted the launch of a powerful CME.

    Observing an Explosion

    An army of spacecraft was on hand to witness the event on 15 Jan 2013 — including the Solar Dynamics Observatory (SDO), the Solar and Heliospheric Observatory (SOHO), and the Solar Terrestrial Relations Observatory (STEREO).



    NASA STEREO spacecraft

    The instruments on board these observatories captured the drama on the northern limb of the Sun as, at 19:32 UT, a coronal jet formed. Just eight minutes later, a powerful CME was released from the same active region.

    The fact that the jet and CME occurred in the same place at roughly the same time suggests they’re related. But did the initial motions of the CME blob trigger the jet? Or did the jet trigger the CME?

    Tying It All Together

    In a recently published study, Liu and collaborators analyzed the multi-wavelength observations of this event to find the heights and positions of the jet and CME. From this analysis, they determined that the coronal jet triggered the release of material to form the CME, which then erupted into space — with the jet at its core — at speeds of over 1000 km/s.

    Based on observed clues of the magnetic field configurations, the team has put together a theory for how this event unfolded. They believe that sudden magnetic reconnection in an active region accelerated plasma to form a large-scale coronal jet. This burst of energy also provided a push on a blob of gas, threaded with magnetic field lines, that lay above the jet. The blob then rose, and when the field lines broke, it was released as a CME with the jet at its core.


    Jiajia Liu et al 2015 ApJ 813 115. doi:10.1088/0004-637X/813/2/115

    See the full article here .

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