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.

SOHO white Light January 2003

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

Sun Spot Number vs. Time

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

SOHO FeXII 195A Movie

CoronalLoops

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

SOHO LASCO X-ray Movie

SOHO LASCO Movie

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

Aurora Borealis

Aurora seen from Space