- 3172 - SUN - how does it get so hot? The visible surface of the sun, or the photosphere, is around 6,000°C. But a few thousand kilometers above it the solar atmosphere, called the corona, is hundreds of times hotter, reaching a million degrees Celsius, 1,000,000 C.
- ----------------------- 3172 - SUN - how does it get so hot?
- The visible surface of the sun, or the photosphere, is around 6,000°C. But a few thousand kilometers above it the solar atmosphere, called the corona, is hundreds of times hotter, reaching a million degrees Celsius, 1,000,000 C.
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- This spike in temperature, despite the increased distance from the sun's main energy source, has been observed in most stars, and represents a fundamental puzzle that astronomers have studied over for decades.
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- In 1942, the Swedish scientist Hannes Alfvén proposed an explanation. He theorized that magnetized waves of plasma could carry huge amounts of energy along the sun's magnetic field from its interior to the corona, bypassing the photosphere before exploding with heat in the sun's upper atmosphere.
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- The theory had been tentatively accepted, but we still needed proof, in the form of empirical observation, that these waves existed. Our recent study has finally achieved this, validating Alfvén's 80 year-old theory and taking us a step closer to harnessing this high-energy phenomenon here on Earth.
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- This represents temperatures up to 1,000 times hotter than the photosphere beneath it, which is the surface of the sun that we can see from Earth. Estimating the photosphere's heat has always been relatively straightforward: we just need to measure the light that reaches us from the sun, and compare it to spectrum models that predict the temperature of the light's source.
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- Over many decades of study, the photosphere's temperature has been consistently estimated at around 6,000°C. Finding that the sun's corona is so much hotter than the photosphere, despite being further from the sun's core, its ultimate source of energy, has led to much head scratching in the scientific community.
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- Scientists looked to the sun's properties to explain this disparity. The sun is composed almost entirely of plasma, which is highly ionized gas that carries an electrical charge. The movement of this plasma in the convection zone which is the upper part of the solar interior produces huge electrical currents and strong magnetic fields.
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- These magnetic fields are then dragged up from the sun's interior by convection, and burble onto its visible surface in the form of dark sunspots, which are clusters of magnetic fields that can form a variety of magnetic structures in the solar atmosphere.
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- This is where Alfvén's theory comes in. He reasoned that within the sun's magnetized plasma any bulk motions of electrically charged particles would disturb the magnetic field, creating waves that can carry huge amounts of energy along vast distances, from the sun's surface to its upper atmosphere. The heat travels along what are called solar magnetic flux tubes before bursting into the corona, producing its high temperature.
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- These magnetic plasma waves are now called Alfvén waves. But, there remained the problem of actually observing these waves. There's so much happening on the sun's surface and in its atmosphere, from phenomena many times larger than Earth to small changes below the resolution of our instrumentation, that direct observational evidence of Alfvén waves in the photosphere has not been achieved before.
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- But recent advances in instrumentation have opened a new window through which we can examine solar physics. One such instrument is the Interferometer Bidimensional Spectropolarimeter (IBIS) for imaging spectroscopy, installed at the Dunn Solar Telescope in the US state of New Mexico. This instrument has allowed us to make far more detailed observations and measurements of the sun.
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- The direct discovery of Alfvén waves in the solar photosphere is an important step towards exploiting their high energy potential here on Earth. They could help us research nuclear fusion which is the process taking place inside the sun that involves small amounts of matter being converted into huge amounts of energy.
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- Our current nuclear power stations use nuclear fission, which critics argue produces dangerous nuclear waste, especially in the case of disasters including the one that took place in Fukushima in 2011.
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- Creating clean energy by replicating the nuclear fusion of the sun on Earth remains a huge challenge, because we'd still need to generate 100 million degrees celsius quickly for fusion to occur. Alfvén waves could be one way of doing this. Our growing knowledge of the sun shows it's certainly possible under the right conditions.
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- The European Space Agency's Solar Orbiter satellite is now in orbit around the sun, delivering images and taking measurements of the star's uncharted polar regions. Terrestrially, the unveiling of new, high-performance solar telescopes are also expected to enhance our observations of the sun from Earth.
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- With many secrets of the sun still to be discovered, including the properties of the sun's magnetic field, this is an exciting time for solar studies. Our detection of Alfvén waves is just one contribution to a wider field that's looking to unlock the sun's remaining mysteries for practical applications on Earth
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- The vast potential of these Alfven waves resides in their ability to transport energy and information over very large distances due to their purely magnetic nature. The direct discovery of these waves in the solar photosphere, the lowest layer of the solar atmosphere, is the first step towards exploiting the properties of these magnetic waves.
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- Alfvén waves form when charged particles (ions) oscillate in response to interactions between magnetic fields and electrical currents.
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- High resolution observations of the solar atmosphere, made by the European Space Agency's imager IBIS, to prove the existence of anti-symmetric torsional waves. These waves could be used to extract vast amounts of energy from the solar photosphere, confirming the potential of these waves for a wide range of research areas and industrial applications.
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- Scientists at Queen's University Belfast have led an international team to the ground-breaking discovery that magnetic waves crashing through the sun may be key to heating its atmosphere and propelling the solar wind.
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- The sun is the source of energy that sustains all life on Earth but much remains unknown about it. For a long time scientists across the globe have predicted that Alfvén waves travel upwards from the solar surface to break in the higher layers, releasing enormous amounts of energy in the form of heat.
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- Over the last decade scientists have been able to prove that the waves exist but until now there was no direct evidence that they had the capability to convert their movement into heat. The heat produced by Alfvén waves in a sunspot was predicted some 75 years ago but we now have the proof for the very first time.
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- By breaking the sun's light up into its constituent colors, our international team of researchers were able to examine the behavior of certain elements from the periodic table within the sun's atmosphere, including calcium and iron.
A sunspot located towards the edge of the Sun, visible here as a dark collection of plasma with magnetic field strengths similar to those found in modern hospital MRI machines. However, it is the size of the sunspot, which is comparable to that of our own Earth (see the scale Earth depicted in the upper-right corner), that gives these structures immense power and energy.
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- Extending upwards from the highly magnetic sunspot are field lines that can guide and direct dynamic motions from within the Sun's deepest layers. The magnetic waves, guided upwards from the surface of the Sun, can form shockwaves that heat the surrounding plasma by thousands of degrees.
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- Once these elements had been extracted, intense flashes of light were detected in the image sequences. These intense flashes had all the hallmarks of the Alfvén waves converting their energy into shock waves, in a similar way to a supersonic aircraft creating a boom as it exceeds the speed of sound.
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- The shock waves then ripple through the surrounding plasma, producing extreme heat. Using supercomputers, we were able to analyze the data and show for the first time in history that the Alfvén waves were capable of increasing plasma temperatures violently above their calm background. ------------------- Other reviews available:
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- 3102 - TEMPERATURE - dimensional analysis to Big Bang? The math used is called “dimensional analysis.” It is a simple concept. To learn it we will try it out on a pendulum before we try it out on the Universe. Measurements in physics and astronomy can involve 3 dimensions: length (space), time, and mass (energy). We refer to these as dimensions and they are measured in units: meters, seconds, kilograms.
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- 3065 - TEMPERATURE - absolute zero degrees. Physicists at the National Institute of Standards and Technology in Boulder, Colorado, chill an aluminum membrane to 0.00036 Kelvin, lower than theory predicted possible for the material. The experiment suggests a way to see quantum effects, like a single object coexisting in two places at once
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- 2946 - TEMPERATURE - a race to the bottom? - Scientists are probing the extreme ends of the spectrum of what’s called “absolute temperature“. At the upper limit, absolute hot is a theoretical furnace where the laws of physics melt away. On the flip side, absolute zero is cold, so cold there’s nowhere to go but up. This absolute zero is almost within scientists’ grasp.
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- 2564 - TEMPERATURE - calculating global Warming? How to measure the temperature of stars? Knowing the temperature of the Earth how to calculate the total energy being radiated? We live on the surface of a 2,000,000,000,000,000 one hundred light bulbs. And, the Sun that is warming us has a surface temperature of 6,000 degrees Kelvin. How do we know these things?
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- 2563 TEMPERATURE - Getting Temperature from Light? If we measure the frequency emitted we know the energy gap between orbits for that particular atom. And , if we know the energy gaps for each element we can measure the frequency of radiation and identify the element that created. it. That is how astronomers know the makeup of stars and gas nebulae that are billions of light years away.
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- 1345 - Absolute zero temperature strangeness.
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- 2349 - What happens when you cool an atom
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- May 25, 2021 SUN - how does it get so hot? 3169
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--------------------- --- Wednesday, May 26, 2021 ---------------------------
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