FYFD

Tag: plasma

  • Thunderstorms Make Trees Glow

    Thunderstorms Make Trees Glow

    Scientists have long hypothesized that the high electrical charge of thunderstorms could produce an opposite charge in the ground that would discharge from the forest canopy. But this phenomenon, known as a corona, had never been observed on actual trees. A new study, however, has observed this ghostly ultraviolet (UV) glow from the tips of sweetgum leaves and loblolly pine needles during thunderstorms.

    Catching these coronae in action required a new kind of UV detector that was ultra-sensitive to the particular band of UV-light emitted by coronas, hot fires, or mercury lamps. Since the latter two weren’t present during the team’s field observations, they were able to conclude that the light they detected came from coronae.

    The group observed that corona discharges were transient, jumping from leaf to leaf and branch to branch across the forest canopy. For any creature capable of detecting that glow by eye, it must be incredible to watch the treetops lit by their own ever-shifting auroras during every thunderstorm. (Image credit: W. Brune; research credit: P. McFarland et al.; via SciAm)

    A UV corona forms on tree leaves beneath a thunderstorm.

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  • Richtmyer-Meshkov Instability

    Richtmyer-Meshkov Instability

    If you send a shock wave through a magnetized plasma–something that happens in both supernova explosions and inertial confinement fusion–it can trigger an instability known as the Richtmyer-Meshkov instability. The image above shows a form of this, taken from a simulation. Rather than treating the plasma as a single idealized fluid, the researchers represented it as two fluids: an ion fluid and an electron fluid. This allowed them to better capture what happens when certain components of the plasma react to changes faster than others do.

    The image itself shows the electron number density across the fluid, where darker colors represent higher electron number density. The interface between high and low-densities shows a roll-up instability that resembles the Kelvin-Helmholtz instability, but there are also regions of mushroom-like plumes that more closely resemble Rayleigh-Taylor instabilities.

    The authors note that these structures don’t appear in simulations that represent a plasma as a single fluid; you need the two-fluid representation to see them. (Image and research credit: O. Thompson et al.)

  • Sprites and ELVES

    Sprites and ELVES

    Although we are most familiar with the white, branching lightning caused by electrical discharge between clouds and the ground, there are many types of lightning. This fortuitous image captures two: tentacled red sprites and ring-like ELVES. Sprites extend upward from the top of a thunderstorm, in a large but weak flash that lasts only seconds. ELVES appear as a rapidly-expanding disc, thought to be caused by an energetic electromagnetic pulse moving into the ionosphere. They were first discovered in footage from a 1992 Space Shuttle mission. (Image credit: V. Binotto; via APOD)

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  • The Twin Roles of Turbulence in Fusion

    The Twin Roles of Turbulence in Fusion

    Inside a fusion reactor, magnetically-contained plasma gets heated to more than one hundred million degrees. That heat, researchers observed, spreads much faster than originally predicted. Now a team from Japan has measurements showing how turbulence manages this feat.

    The researchers show that the multiscale nature of turbulence allows it to transport heat in two ways. The first is familiar: acting locally, turbulence spreads heat little by little as small eddies mix and pass the heat along. But turbulence can also be nonlocal, they show, able to connect physically distant parts of a flow more rapidly than expected. This happens through turbulence’s larger scales, which can rapidly carry heated plasma from one side of the vessel to another.

    The researchers illustrate the two roles of turbulence through a metaphor of American football (can you believe it?). In their metaphor, the quarterback acts as turbulence and the ball represents heat. The quarterback can pass the ball to reach distant parts of the field quickly — just as nonlocal turbulence does–or they can hand off the ball to a running back, who carries the ball down the field more slowly, through local interactions with other nearby players. (Image credit: National Institute for Fusion Science; research credit: N. Kenmochi et al., via Gizmodo and EurekAlert)

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  • Shining in the Sky

    Shining in the Sky

    Shades of blue, green, and purple light the Icelandic sky in this image from December 2023. Incoming solar wind particles hit oxygen and nitrogen atoms high in the atmosphere, exciting their electrons and creating this distinctive glow. We’re currently near the peak of our Sun’s 11-year solar cycle, meaning that high numbers of sunspots and outbursts will continue, likely giving us more stunning auroras like this one. (Image credit: J. Zhang; via APOD)

    An aurora in shades of blue, green, and purple.
    An aurora in shades of blue, green, and purple.

    P.S. – This post–this one right here–is FYFD’s 4000th post! When I started this blog back in 2010 as a graduate student, I never imagined that I would have so much to write about the physics of fluids. But this subject is one that just keeps on giving, so I keep on writing. Thanks for joining the fun! – Nicole

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  • Zoom Into the Sun

    Zoom Into the Sun

    Fall into our nearest star in this gorgeous high-resolution view of the Sun. Taken by Solar Orbiter, a joint NASA-ESA mission, the image stretches from the fiery photosphere — full of filaments and prominences — to the wispy yet unbelievably hot corona. It’s well worth clicking through to zoom in and around the full size image. (Image credit: ESA & NASA/Solar Orbiter/EUI Team, E. Kraaikamp; via Gizmodo)

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  • A Glimpse of the Solar Wind

    A Glimpse of the Solar Wind

    In December 2024, Parker Solar Probe made its closest pass yet to our Sun. In doing so, it captured the detailed images seen here, where three coronal mass ejections — giant releases of plasma, twisted by magnetic fields — collide in the Sun’s corona. Events like these shape the solar wind and the space weather that reaches us here on Earth. The biggest events can cause beautiful auroras, but they also run the risk of breaking satellites, power grids, and other infrastructure. (Image credit: NASA/Johns Hopkins APL/Naval Research Lab; video credit: NASA Goddard; via Gizmodo)

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  • A New Plasma Wave for Jupiter

    A New Plasma Wave for Jupiter

    Jupiter‘s North Pole has a powerful magnetic field combined with plasma that has unusually low electron densities. This combination, researchers found, gives rise to a new type of plasma wave.

    Ions in a magnetic field typically move parallel to magnetic field lines in Langmuir waves and perpendicularly to the field lines in Alfvén waves — with each wave carrying a distinctive frequency signature. But in Jupiter’s strong magnetosphere, low-density plasma does something quite different: it creates what the team is calling an Alfvén-Langmuir wave — a wave that transitions from Alfvén-like to Langmuir-like, depending on wave number and excitation from local beams of electrons.

    Although this is the first time such plasma behavior has been observed, the team suggests that other strongly-magnetized giant planets — or even stars — could also form these waves near their poles. (Image credit: NASA / JPL-Caltech / SwR I/ MSSS/G. Eason; research credit: R. Lysak et al.; via APS)

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  • A Sprite From Orbit

    A Sprite From Orbit

    A sprite, also known as a red sprite, is an upper-atmospheric electrical discharge sometimes seen from thunderstorms. Unlike lightning, sprites discharge upward from the storm toward the ionosphere. This particular one was captured by an astronaut aboard the International Space Station. That’s a pretty incredible feat because sprites typically only last a millisecond or so. The first one wasn’t photographed until 1989. (Image credit: NASA; via P. Byrne)

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  • Glimpses of Coronal Rain

    Glimpses of Coronal Rain

    Despite its incredible heat, our sun‘s corona is so faint compared to the rest of the star that we can rarely make it out except during a total solar eclipse. But a new adaptive optic technique has given us coronal images with unprecedented detail.

    A solar prominence dancing in the Sun's magnetic field lines.

    These images come from the 1.6-meter Goode Solar Telescope at Big Bear Solar Observatory, and they required some 2,200 adjustments to the instrument’s mirror every second to counter atmospheric distortions that would otherwise blur the images. With the new technique, the team was able to sharpen their resolution from 1,000 kilometers all the way down to 63 kilometers, revealing heretofore unseen details of plasma from solar prominences dancing in the sun’s magnetic field and cooling plasma falling as coronal rain.

    Coronal rain -- cooler plasma falling back down along magnetic lines.

    The team hope to upgrade the 4-meter Daniel K. Inouye Solar Telescope with the technology next, which will enable even finer imagery. (Image credit: Schmidt et al./NJIT/NSO/AURA/NSF; research credit: D. Schmidt et al.; via Gizmodo)