solar theory (mt 4510) clare e parnell school of mathematics and statistics
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Solar TheorySolar Theory(MT 4510)(MT 4510)
Clare E ParnellClare E ParnellSchool of Mathematics and School of Mathematics and
StatisticsStatistics
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Sun FactsSun Facts
1 400 kg/m1 400 kg/m33
1/4 x Earth’s density1/4 x Earth’s density5 500 5 500 kg/mkg/m33
DensitDensityy
2 x 102 x 103030 kg kg
333 000 x Earth’s mass333 000 x Earth’s mass6 x 106 x 102424 kgkg
MassMass
1.41 x1.41 x 10101818 km km33
1 300 000 x Earth’s 1 300 000 x Earth’s volumevolume
1.1 x 101.1 x 101212 kmkm33
VolumVolumee
696 000 km696 000 km
109 x Earth’s radius109 x Earth’s radius66 400400 kmkmRadiusRadius
SunSunEarthEarth
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Sun FactsSun Facts
4 x 104 x 1026 26 WW
4 x 104 x 1024 24 light bulbslight bulbsLuminositLuminosityy
149 000 000 km149 000 000 km
23 000 x Earth’s 23 000 x Earth’s radiusradius
Distance Distance from Earthfrom Earth
25 days - equator25 days - equator
33 days - poles33 days - poles
‘‘differential rotation’differential rotation’
1 day1 dayRotation Rotation raterate
Electrically charged Electrically charged gasgas
(plasma) core: (plasma) core: hydrogenhydrogen
Solid core: Solid core: ironiron
ConsistenConsistencycy
SunSunEarthEarth
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Sun’s Nuclear CoreSun’s Nuclear Core• Fusion of hydrogen in core produces gamma rays
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Solar InteriorSolar InteriorCore
(T~1.6x107 K)
Radiative Zone(T~8x106 K)
Convection Zone(T~2x106 K)
Photosphere(surface)
(T~6400 K)
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HelioseismologyHelioseismology• Used to study the interior of the Sun
• It is the study of resonant wave modes of oscillation of the Sun
• Modes of oscillation are visible manifestations of trapped standing sound waves
• Strongest periods ~ 5 Strongest periods ~ 5 minsmins
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Solar Rotation RateSolar Rotation Rate• Relative rotation rates of material in the Sun - determined using helioseismology
• Red material – fastest
• Dark blue – slowest
• Interior: red moves ~ 4% faster than outer layers.
• Surface: red (equator) moves ~ 3,000 mph faster than blue (poles).
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Observing Sun’s Observing Sun’s AtmosphereAtmosphere
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Solar AtmosphereSolar Atmosphere
Photosphere(6600 K>T> 4300 K)
Chromosphere(4300 K<T<106 K)
Corona(T>106 K)
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PhotospherePhotosphere• T ~ 6600-4300 K• ρ ~ 10-8th of water• P ~ 10-2th of
atmosphere• H ~ 100 km
• Visible light images reveal sunspots• Magnetograms
reveal surface magnetic fields• Field into Sun – black• Field out of Sun -
white
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ChromosphereChromosphere• 4300 K < T < 106 K• ρ ~ 10-8-10-14 less
than water• P ~ not much!• H ~ 2500 km
• Observed in many wavelengths, e.g.,• Ca II K• H alpha• 304 Å
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CoronaCorona• T > 106 K (low
corona)• ρ < 10-14 less than
water• P ~ even less!• H - to Earth &
beyond!
• Observed in• EUV (T~106 K)• Soft X-ray (T> 2x106 K)• Visible (white) light
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Coronal Heating ProblemCoronal Heating Problem
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CoronaCoronaCoronal holeX-ray bright point
Active region Coronal loops
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Solar CycleSolar Cycle
Solar Maximum
SolarMinimum
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Umbra Penumbra
SunspotsSunspots
• Magnetic field strength ~ 2-3x103 G
• Umbra – vertical field
• Penumbra – horizontal field
• Number of sunspots varies over 11 year cycle
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ProminencesProminences
• Situated in corona• Cool, dense plasma
confined in vertical sheets
• Lifetimes: days-months
• Size: 2x105 x 5x104 x 6x103 km3 (LxHxW)
• ρ: 10-12 kg cm-3
• T: 5-10 x103 K
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Solar FlaresSolar Flares• Sudden, impulsive,
intense, large-scale, heating events
• Very energetic: from 1022 - 1025 J
• Lifetimes: hours
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Coronal Mass Ejections Coronal Mass Ejections (CMEs)(CMEs)
• Very large Very large events that eject events that eject mass from the mass from the SunSun
• Energy: 10Energy: 102525 J J• Mass: 10Mass: 101313 kg kg• Lifetime: hoursLifetime: hours• Usually related Usually related
to a prominence to a prominence eruptioneruption
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Solar WindSolar Wind
• Ions and electrons Ions and electrons continually stream continually stream out along magnetic out along magnetic field linesfield lines
• Solar wind:Solar wind:– Strong above poles Strong above poles
(open field)(open field)– Weak about equator Weak about equator
(closed field)(closed field)
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Sun-Earth ConnectionSun-Earth Connection
• Solar wind continually buffets Earth’s magnetic field
• CME’s can disrupt Earth’s magnetic field and cause Auroras
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The Sun Today!The Sun Today!EIT 304 EIT 171 EIT 195 EIT 284
LASCO C3LASCO C2MDI MAGMDI CONT
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Solar Theory CourseSolar Theory Course
Outline structure of Outline structure of eventsevents
Maxwell’s equations Maxwell’s equations and magnetic fieldsand magnetic fields
11
Sun/Earth connectionSun/Earth connectionSolar windSolar wind66
Helio/coronal-Helio/coronal-seismology, coronal seismology, coronal heating, solar windheating, solar wind
MHD wavesMHD waves55
Coronal arcades and Coronal arcades and loop structures, loop structures, prominencesprominences
MHD equilibriaMHD equilibria44
Flares, CMEs, coronal Flares, CMEs, coronal heating, solar windheating, solar wind
Magnetic Magnetic reconnection and reconnection and magnetic energymagnetic energy
33Describe behaviour of Describe behaviour of SunSun
MHD equationsMHD equations22
ImportanceImportanceTopicTopic§§
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The Sun (Summary)The Sun (Summary)