The Sun’ Energy Production Mechanism & the Earth — Sun Connection Astronomy 104 ; Lecture 1 April 5, 2004 Guest Lecture by Professor Christopher M. Anderson

The Sun ‘s Energy Source ? (1) Energy Equilibrium - “Energy lost = Energy produced” So, what are energy sources for Sun’s luminosity? 1.Chemical, C + O 2  CO 2 Adequate for perhaps 10,000 years 2.Gravity, E = GM /  R Adequate for perhaps 200,000 years Adequate for perhaps 200,000 years 3. Nuclear E =  m C 2 Energy(joules) Change in Mass(kg) Speed of light (3 x 10 8 m/sec) Squared Adequate for 10 x 10 9 (billion) years or more

The Sun’s Energy Source ! (2) Thermonuclear Hydrogen Fusion 4 H  He 4 H = 4 x x kg = x kg Fuel Mass 4 H = 4 x x kg = x kg Fuel Mass -1 He = x kg Left Over Mass -_________________________________________ x kg Change,  m x kg Change,  m (0.048 x kg) * (3 x 10 8 m/s) 2 = 4.3 x joules That’s from 6.7x kg of fuel, So from 1 kg we get E = 6.4 x Joules So from 1 kg we get E = 6.4 x Joules The Mass of the Sun is, M = 2 x kg The Sun’s Energy Output ( Luminosity ) L = 3.9 x Joules s -1 So the Sun can do what it’s doing now for a time   = = = = M x E L 2 x kg x 6.4 x J kg x J s -1 = = 3.3 x10 18 s  = years

Overcoming Electrostatic Repulsion Why “Thermonuclear”? Positive charges Repel One another Very Strongly So it REQUIRES BOTH High Density (so it happens often) But Especially But Especially Very High Speed i.e. VERY HIGH TEMPERATURE

The Proton – Proton Chain Thermonuclear Hydrogen Fusion 4 H  He But if getting two + Charged particles together is difficult Getting 4 at once together is REALLY tough So what’s needed is a “setp-wise” process Positron Neutrino Deuterium 2 Protons i.e. Hydrogen Nuclei Helium 4 Helium 3 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 Diagram N S NS Sun Spot Number v Time George E. Hale Spot Magnetic Fields Magnetic 1908 NS N S Hale & Nicholson Systematics of Bipolar Magnetic Regions Bipolar 1925 “ Maunder Minima” Particularly Severe Winters

Spectrograph Slit Over Sun Spot

Zeeman Effect Spectrum

SOHO Magnetogram 11/06/2001

SOHO FeXII 195A Movie

Coronal Loops

Solar Corona, 1991 Eclipse T ~ 10 6 K Outflow (Solar Wind) V ~ 500 km s -1 N electron = N proton ~ 1 cm -3 (at 1a.u )

Solar Activity, Some Facts & Figures (1) Flares Flares Release of up to Joules in 10 – 100 minutes Release of up to Joules in 10 – 100 minutes Radio & X-ray Bursts, seen immediately Radio & X-ray Bursts, seen immediately Correspond to gas at T ~ 10 7 K Correspond to gas at T ~ 10 7 K High particle ( 1 H & e - ) Earth, 1 – 5 days later High particle ( 1 H & e - ) Earth, 1 – 5 days later Frequency Frequency at Solar Max, 1500 yr -1 at Solar Max, 1500 yr -1 at Solar Min, only 40 yr -1 at Solar Min, only 40 yr -1 Origin ? : “Magnetic Reconnection Events” Origin ? : “Magnetic Reconnection Events” Coronal Mass Ejection Coronal Mass Ejection

SOHO LASCO X-ray Movie

SOHO LASCO Movie

Solar Activity, Some Facts & Figures (2) Flares Flares Release of up to Joules in 10 – 100 minutes Release of up to Joules in 10 – 100 minutes Radio & X-ray Bursts, seen immediately Radio & X-ray Bursts, seen immediately Correspond to gas at T ~ 10 7 K Correspond to gas at T ~ 10 7 K High particle ( 1 H & e - ) Earth, 1 – 5 days later High particle ( 1 H & e - ) Earth, 1 – 5 days later Frequency Frequency at Solar Max, 1500 yr -1 at Solar Max, 1500 yr -1 at Solar Min, only 40 yr -1 at Solar Min, only 40 yr -1 Origin ? : “Magnetic Reconnection Events” Origin ? : “Magnetic Reconnection Events” Coronal Mass Ejection Coronal Mass Ejection Mass expelled ~ 3 x kg Mass expelled ~ 3 x 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 ~ Joules Energy, also ~ Joules Speed of ejection ~ 500 – 1500 km s -1 Speed of ejection ~ 500 – 1500 km s -1 Much of it in the plane of the Ecliptic Much of it in the plane of the Ecliptic

Aurora Borealis

Aurora seen from Space