The Sun
description
Transcript of The Sun
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The Sun
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Solar Structure
• Core• Radiative zone• Convective zone• Atmosphere
– Photosphere– Chromosphere– Corona
• Solar wind (mass loss)
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Conditions Inside the Sun
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Solar PowerSun’s glow fueled by Nuclear Fusion
– Fusion is a process by which lighter atoms undergo “collisions” that spawn heavier atoms and a release of energy for radiation
– Fission, on the other hand, is when a heavy atom “breaks up” to yield a lighter atom plus energy
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Proton-Proton Chain
• p-p chain converts 41H into 14He(so 4 bare protons combine to make a helium nucleus with 2p’s and 2n’s)
• Also get photons and neutrinos in this process
• Neutrinos are (nearly) massless particles traveling near light speeds and interacting only weakly with matter
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The Chain
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Emergence of Light from the Core
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Solar Neutrinos• Neutrinos are elementary particles moving near light speed, but which interact only weakly with matter.
• They are important because they can come from nuclear reactions to emerge directly from the core of the Sun.
• Raymond Davis arranged for the first neutrino experiment. He discovered a “neutrino problem”, but this has now been resolved.
A modern neutrino experiment,Super-Kamiokande run by Japan
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The Chain
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Solar Atmosphere
• Photosphere: the layer that we “see” in visible light
• Chromosphere: tenuous, somewhat hotter layer above photosphere
• Corona: extended region of million degree gas above chromosphere extending into space and the solar wind
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Perspectives of the Sun
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A Solar Eclipse
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The Transition Region
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Solar Activity
• Sunspots – cool blemishes that come and go on an 11 year cycle– During cycle, spots initially appear at high latitudes and thereafter at progressively lower lats.
• Prominences – extended columns of gas that trace out magnetic loops (can rise to 50,000 km above photosphere)
• Flares – explosive and energetic events involving hot gas of up to 40 million K
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Solar Granulation - Convective Cells
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Sunspots
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Spicules
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The Active Sun
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Prominences
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Magnetic Loops at the Sun
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Solar Cycle in X-rays
X-ray emission from the solar corona, taken every 120 days, from 1991 (left) to 1995 (going right)
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Solar Cycle in the UV
Images of the Sun in Extreme UV radiation
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Butterfly Diagram
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Understanding The Solar Cycle
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The Solar Cycle in Magnetism
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Sun-Earth Connection
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Solar Cycle and the Earth’s Climate
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The Solar Wind
• 1951, Biermann discovered solar wind by considering comet tails
• Speed near earth is around 400 km/s with a travel time across 1 AU of ~4 days
• Combination of the wind outflow and the magnetic field have caused a “spin down” of Sun’s rotation over time
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Solar Wind Mass Flux
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Space Weather
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The Resonating Sun
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Long-Term Changes in the Sun
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The Sun in Time
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Solar Sailing: Propulsion in the Future?
• To make G > 1 requires a material with (A/m) > 1300 m2/kg (equivalent to 36m x 36m)
• For 1 kg of sail, and G = 2, Fnet = 0.006 N