The Sun’ Energy Production Mechanism & the Earth — Sun Connection Astronomy 104 ; Lecture 1...
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Transcript of The Sun’ Energy Production Mechanism & the Earth — Sun Connection Astronomy 104 ; Lecture 1...
The Sun’ Energy Production MechanismThe Sun’ Energy Production Mechanism&&
the Earth — Sun Connection the Earth — Sun Connection
Astronomy 104 ; Lecture 1Astronomy 104 ; Lecture 1
April 5, 2004 Guest Lecture April 5, 2004 Guest Lecture byby
Professor Christopher M. AndersonProfessor Christopher M. Anderson
The Sun ‘s Energy Source ? The Sun ‘s Energy Source ? (1)(1)
Energy Equilibrium - “Energy lost = Energy produced”Energy Equilibrium - “Energy lost = Energy produced”So, what are energy sources for Sun’s luminosity?So, what are energy sources for Sun’s luminosity?1.1. Chemical, C + OChemical, C + O22 CO CO22
Adequate for perhaps 10,000 yearsAdequate for perhaps 10,000 years2.2. Gravity, E = GM / Gravity, E = GM / RR
Adequate for perhaps 200,000 yearsAdequate for perhaps 200,000 years3. Nuclear3. Nuclear
E = m C2
EnergyEnergy(joules)(joules)
Change inChange inMassMass(kg)(kg)
Speed of light (3 x 10Speed of light (3 x 1088 m/sec) m/sec) SquaredSquared
Adequate for 10 x 10Adequate for 10 x 1099 (billion) years or more (billion) years or more
Overcoming Electrostatic RepulsionOvercoming Electrostatic RepulsionWhy “Thermonuclear”?
Positive charges Repel One another Very Strongly
So itSo itREQUIRES BOTHREQUIRES BOTH
High DensityHigh Density(so it happens often)(so it happens often)
But But EspeciallyEspeciallyVery High Speed Very High Speed
i.e. i.e. VERY HIGHVERY HIGH
TEMPERATURETEMPERATURE
The Proton – Proton ChainThe Proton – Proton ChainThermonuclear Hydrogen Fusion 4 H Thermonuclear Hydrogen Fusion 4 H He He
But if getting two + Charged particles together is difficultBut if getting two + Charged particles together is difficultGetting 4 at once together is REALLY toughGetting 4 at once together is REALLY tough
So what’s needed is a “setp-wise” processSo what’s needed is a “setp-wise” process
Positron
Neutrino
Deuterium
2 Protonsi.e.
HydrogenNuclei
Helium 4
Helium 3
1 1 1H H D e
1 2 3H H He
3 3 4 12He He He H
2e e
Do Steps 1 & 2
A second time
White Light Sun
“ I am at last convinced that the spots are objects close to the surface of the
solar globe … also that they are carried around the Sun by its rotation”
---- Galileo 1613, Historia e Dimostrazioni intorno alle Macchie Solari
Quotation recovered from Baliunas et al. 1995, ApJ 438, 269.
Sun Spots & Granulation
Normal Photosphere Temperature =5700 K
Sun Spot “Umbra” Temperature = 4200 K
•Granulation•Size ~ 1000 km• T ~ 150 K• Life time ~ 10 min• Tops of Convection Cells
T ~ 1500 K
The Maunder The Maunder DiagramDiagram
NS
N S
Sun Spot Number v TimeSun Spot Number v Time
George E. Hale George E. Hale Spot Spot Magnetic Fields
19081908
N S
NSHale & NicholsonHale & NicholsonSystematics of Systematics of
Bipolar Magnetic Magnetic RegionsRegions
19251925
“ Maunder Minima”
Particularly Severe Winters
Solar Corona, 1991 Eclipse
T ~ 106 K
Outflow (S
olar W
ind)
V ~ 500 km s-1
N electr
on = N proton
~ 1 cm-3 (
at 1a.u
)
Solar Activity, Some Facts & Figures Solar Activity, Some Facts & Figures (1)(1)
• FlaresFlares• Release of up to 10Release of up to 102323 Joules in 10 – 100 minutes Joules in 10 – 100 minutes
• Radio & X-ray Bursts, seen immediatelyRadio & X-ray Bursts, seen immediately• Correspond to gas at T ~ 10Correspond to gas at T ~ 1077 K K
• High particle (High particle (11H & eH & e--) Flux @ Earth, 1 – 5 days later) Flux @ Earth, 1 – 5 days later• FrequencyFrequency
• at Solar Max, 1500 yrat Solar Max, 1500 yr-1-1
• at Solar Min, only 40 yrat Solar Min, only 40 yr-1-1
• Origin ? : “Magnetic Reconnection Events”Origin ? : “Magnetic Reconnection Events”• Coronal Mass EjectionCoronal Mass Ejection
Solar Activity, Some Facts & Figures Solar Activity, Some Facts & Figures (2)(2)
• FlaresFlares• Release of up to 10Release of up to 102323 Joules in 10 – 100 minutes Joules in 10 – 100 minutes
• Radio & X-ray Bursts, seen immediatelyRadio & X-ray Bursts, seen immediately• Correspond to gas at T ~ 10Correspond to gas at T ~ 1077 K K
• High particle (High particle (11H & eH & e--) Flux @ Earth, 1 – 5 days later) Flux @ Earth, 1 – 5 days later• FrequencyFrequency
• at Solar Max, 1500 yrat Solar Max, 1500 yr-1-1
• at Solar Min, only 40 yrat Solar Min, only 40 yr-1-1
• Origin ? : “Magnetic Reconnection Events”Origin ? : “Magnetic Reconnection Events”• Coronal Mass EjectionCoronal Mass Ejection
• Mass expelled ~ 3 x 10Mass expelled ~ 3 x 101313 kg kg• ~ 2 km cube of rock (but of course it’s mostly Hydrogen)~ 2 km cube of rock (but of course it’s mostly Hydrogen)
• Energy, also ~ 10Energy, also ~ 1023 23 JoulesJoules• Speed of ejection ~ 500 – 1500 km sSpeed of ejection ~ 500 – 1500 km s-1-1
• Much of it in the plane of the EclipticMuch of it in the plane of the Ecliptic