Chapter 12Properties of the SunInterior of the SunEnergy Flow with in the SunThe Solar AtmosphereHow the Sun WorksThe Sun’s Power SourceThe Proton-Proton ChainProbing the Sun’s CoreSolar Magnetic ActivitySlide 11Solar Magnetic ActivityThe Sun at Different Wavelengths (image from NASA)Why is the Corona so hot?Solar Wind (image from NASA)The Solar CycleThe Solar CycleStill doesn’t explain global warmingChapter 12The Sun, Our StarProperties of the Sun•Interior of the Sun•Photosphere: how far into the Sun we can see.•Pressure and temperature both rise as you move toward the core.•Density in the photosphere similar to density of air on surface of Earth.Energy Flow with in the Sun•Three main zones.•Heat flows from inside (hottest) to outside (coldest)•Convection zone creates surface features we can see.The Solar Atmosphere•Two main regions:Chromosphere/Corona•Temperature rises, pressure drops as altitude increases.•Chromosphere: Thin red lineRanges from 4,500K to 50,000K.“Spicules”•Corona:1 million KelvinNot uniformly shapedHow the Sun Works• Hydrostatic Equilibrium•Computer models of the interior:Core is 15 million K•Sun loses heat, so it must have a source for new energyThe Sun’s Power Source•Nuclear Fusion•Mechanism published in 1930s.•E = mc2•So hot that electrical repulsion is overwhelmed by the strong force.•State of matter is technically a “plasma” not a gas.The Proton-Proton Chain1. 1H + 1H —> 2H + e+ + �(neutrino)2.1H + 2H —> 3He + �(photon: gamma ray)3.3He + 3He —> 4He + 1H + 1Hm4H - m1He = 4.8 * 10-29 kg4.8 * 10-29 kg * c2 = 4.3 * 10-12 J4 millions tons of mass converted EACH SECONDProbing the Sun’s Core•Solar neutrinos•Neutrinos super hard to detect, initially found only 1/3 of expected•Solar seismology•Analyze waves on surface of SunSolar Magnetic Activity• Charges follow field lines. Large-scale motion of charges can pull field lines with the charges.•Sunspots: Cooler than rest of surface. Strong field disturbs convection.•Prominences: Plumes of glowing gas.•Zeeman effect•Sunspots have polaritySolar Magnetic Activity• Solar Flares: •Brief bright eruptions x-rays and other photons•Thought to be caused by magnetic field readjusting•8 minutes to reach Earth•Coronal Mass Ejections:•Similar, but charged particles are emitted rather than photons.•1-3 days to reach Earth•Both have consequences for Earth.•Similar phenomena, but not the same thing. Don’t always occur together.•Shame on your textbook.The Sun at Different Wavelengths (image from NASA)•Why is the Corona so hot?•More magnetic energy per particle as density gets lower.•Temperature is a measure of how much the atoms are moving.•These waves are generated within the Sun.Solar Wind(image from NASA)• Atoms escaping Sun’s gravity•The Corona is NOT in hydrostatic equilibrium•Starts slow, eventually 500 km/sec til past Neptune•New from Voyager and Voyager 2 (since textbook was published): Around 116 AU, the wind dies down•Solar sailsThe Solar Cycle•The Solar Cycle•Each 11 year cycle reverse the polarity•Maunder minimum:•Unusually cold winters on Earth•Not the only such incidence.•Magnetic field heats corona. Corona drives solar wind. Solar wind changes how temperature varies with altitude. This alters circulation of air, jet streams, and rainfall pattern.Still doesn’t explain global
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