plasma

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The upper atmosphere of the Sun is dominated by plasma filled magnetic loops (coronal loops) whose temperature and pressure vary over a wide range. The appearance of coronal loops follows the emergence of magnetic flux, which is generated by dynamo processes inside the Sun. Emerging flux regions (EFRs) appear when magnetic flux bundles emerge from the solar interior through the photosphere and into the upper atmosphere (chromosphere and the corona). The characteristic feature of EFR is the -shaped loops (created by the magnetic buoyancy/Parker instability), they appear as developing bipolar sunspots in magnetograms, and as arch filament systems in . EFRs interact with pre-existing magnetic fields in the corona and produce small flares (plasma heating) and collimated plasma jets. The GIFs above show multiple energetic jets in three different wavelengths. The light has been colorized in red, green and blue, corresponding to three coronal temperature regimes ranging from ~0.8Mk to 2MK. 

Image Credit: SDO/U. Aberystwyth

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Earth is not the only planet in our solar system with auroras. As the solar wind–a stream of rarefied plasma from our sun–blows through the solar system, it interacts with the magnetic fields of other planets as well as our own. Saturn’s magnetic field second only to Jupiter’s in strength. This strong magnetosphere deflects many of the solar wind’s energetic particles, but, as on Earth, some of the particles get drawn in along Saturn’s magnetic field lines. These lines converge at the poles, where the high-energy particles interact with the gases in the upper reaches of Saturn’s atmosphere. As a result, Saturn, like Earth, has impressive and colorful light displays around its poles. (Image credit: ESA/Hubble, M. Kornmesser & L. Calçada, source video; via spaceplasma)

During a solar flare, magnetic field lines on the sun are often visible due to the flow of plasma–charged particles–along the lines. According to theory, these magnetic lines should remain intact, but they are sometimes observed breaking and reconnecting with other lines. An interdisciplinary team of researchers suggests that turbulence may be the missing link. In their magnetohydrodynamic simulation, they found that the presence of chaotic turbulent motions made the magnetic line motion entirely unpredictable, whereas laminar flows behaved according to conventional flux-freezing theory. (Photo credit: NASA SDO; Research credit: G. Eyink et al.; via SpaceRef; submitted by jshoer)

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Heliophysics - Studying Our Star

Viewing our Sun’s light in different wavelengths allows scientists to isolate and analyze its behavior. The yellow image highlights the outer atmosphere of the Sun - called the corona - as well as hot flare plasma. The red image show’s a detailed view of cooler dense plumes of plasma. The blue and violet (taken in Extreme Ultraviolet) images give a map of radiation and coronal mass ejections.

Credit: NASA / Solar Dynamics Observatory

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Two Ribbon Flare

On September 29. 2013, a large magnetic filament erupted on the Sun’s northern hemisphere and produced a C1.2 solar flare. Observation in the EUV showed two elongated ribbon-like structures (hence, the term two-ribbon flare) symmetrically developing on either side of the active region, along the polarity inversion line (neutral line). Two-ribbon flares are extremely powerful eruptions; during magnetic reconnection the magnetic energy is converted into radiation across the electromagnetic spectrumenergetic particles are accelerated up to several hundred MeV or even to GeV range. These high-energy particles are called solar cosmic rays.

Credit & source: LMSAL/Scott Green

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Engineers frequently face the challenge of maintaining control of air flow around an object across a wide range of conditions. After all, wind turbines and airplanes don’t always get to choose the perfect weather. To widen their operating ranges, designers can use active flow control to keep air flowing around an airfoil instead of separating and causing stall. One method of flow control uses plasma actuators on the upper surface of an airfoil. When activated, the plasma actuator ionizes air near the wing surface, producing the purplish glow seen above. That ionized air, or plasma, gets accelerated by the electric field of the device. The acceleration adds momentum to air near the wing surface, which helps it stay attached and flowing smoothly despite the unfavorable pressure conditions near the trailing edge of the wing. Compared to other methods of active flow control, plasma actuation is relatively simple to implement and so is actively being researched for applications in aviation and wind energy. (Image credit: N. Fine et al., source; M. Debiasi et al.