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(Space Climate School, Saariselka, March, 2009)

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Presentation on theme: "(Space Climate School, Saariselka, March, 2009)"— Presentation transcript:

1 (Space Climate School, Saariselka, March, 2009)
I. OUR OWN SUN (Space Climate School, Saariselka, March, 2009) Eric Priest (St Andrews)

2 space physics/astronomy
1. Why Study the Sun ? 1. Of great scientific interest in own right 2. Influence on Earth 3. Important for Astronomy -- fundamental cosmic processes 4. Many misconceptions….. Many basic properties still mystery (astrony) - interior, dynamo, corona, wind, flares So Sun is 1 of liveliest branches of space physics/astronomy

3 Another Theme: Many surprises caused by magnetic field (B)
Sun is NOT a normal gas Sun is in 4th state of matter ("PLASMA") behaves differently from normal gas: B and plasma -- coupled (intimate, subtle) B exerts force on plasma -- stores energy

4 2. The SUN Vital Statistics ? Chemical composition Radius Age --

5 Overall Structure Interior: Core Convection zone
Atmosphere: Photosphere, Chromosphere, Corona

6 Covered with turbulent convection cells: “Granulation” (1 Mm)
3. Photosphere Temperature K Covered with turbulent convection cells: “Granulation” (1 Mm) “Supergranulation” ( Mm)

7 In close-up: points, flowers, ribbons (created by magnetic fields)

8 Dark because cool But why cool ?
SUNSPOTS Photosphere --> Sunspots Harriot discovered (1610) w. telescope Dark because cool But why cool ?

9 New Model (Thomas & Weiss)
Mixture: Dark filaments- (low) Bright filaments- (high)

10 Map of Photospheric Magnetic Field
White -- towards you; Black -- away from you Regions around sunspots -- bipolar "Active Regions"

11 SURPRISES: -- B carried to edges of convection cells
1. Intense magnetic fields over whole Sun B carried to edges of convection cells 2. Patterns of sunspots/act. regs -- large flux tube --> dynamo …

12 Old Picture Atmosphere - static, T(r)

13 But - atmosphere is inhomogeneous
Many temperatures in same region

14 4. Chromosphere is dynamic (2D Simulation)
[Hansteen & Carlsson] Corona Chromo- sphere Photo- sphere (light/ dense)

15 Dynamic nature s. atmosphere Swedish Solar Telescope
Quiet active region H-alpha 0.1 arcsec Continually-changing threads

16 5. CORONA Heating caused by magnetic field
("crown") -- See at ECLIPSE of Sun 5. CORONA Along open structures: -- fast solar wind SURPRISE (1940) -- Temperature is million degrees Students in St Andrews imaginative: Heating caused by magnetic field Structure outlines magnetic field

17 Total Eclipse - March 29, 2006 - Motion of Moon’s shadow


19 Over 1.5 hours: Light level decreases, Cooler, Shadows sharpen

20 In last 10 minutes: Light level and temperature decrease more quickly
Wind Start to see planets Just before totality (when Moon covers Sun) -- Baily beads Red chromosphere Prominences Corona - glowing against jet black disc !

21 Just before totality 2nd Contact Magnetic tubes “prominences”



24 CORONA: Observe direct with EUV/X-ray telescope
Normally need eclipse to see -- Glare of surface Observe direct with EUV/X-ray telescope As T increases (furnace), object becomes bluer

25 Picture with X-ray telescope:
Coronal holes -- loops -- bright points Bright --> Denser

26 Hinode X-ray Telescope (2006--..)

27 6. SOHO (Solar & Heliospheric Observatory)
Launched Orbiting Sun at point in phase with Earth Observing Sun continuously for 1st time (ESA/NASA) --> 1st comprehensive view of Sun MANY NEW SURPRISES

28 QN. -- ? Earth Influenced by Solar Variability
Number of Sunspots Oscillates w. 11-year Cycle

29 Solar Cycle Sunspots - two zones between -35o and +35o latitude
Leading spots have opposite polarities in 2 hemispheres [Hale] Leading polarity is closer to equator [Joy] Magnetic field reverses every 11 years

30 Solar cycle (ii) Spots emerge at high latitudes w. opposite polarity
Sunspot minm -- no spots -- polar fields Spots emerge at high latitudes w. opposite polarity [later at lower latitudes] 90% active region flux cancels --10 % migrates -- following flux reaches poles reduces & reverses polar field-- new minm Global coronal magnetic field goes thro’ complex set of 17 topologies (Maclean & Priest, 2007) [Polar Fields: * maximum extent at s. minimum * change polarity 1-2 years after s. maximum]

31 Whole atmosphere varies with cycle
Max Min Chromosphere Corona (Intensity Changes by 100) Schematic --> eq. streamers/polar holes

32 Solar wind velocity [polar plot, ULYSSES]
Sunspot minimum [ ] FAST Solar Wind (700 km/s) in coronal holes SLOW Solar Wind (300 km/s) in equatorial streamers [Red = inward field Blue = outward field]

33 SURPRISE (1976) Realised NO sunspots in most of 17th centy
"Maunder Minimum" -- Little Ice Age So B on Sun affects climate of Earth !! But mechanism not known !

34 SOHO --> Total Emission (t) 1996-2000
Emission varies by 0.2% -- passage sunspots Increase by 0.1% from sunspot min to max Much too small to produce global warming ?? Real & ?? cause

35 Solar cycle variations further back to:
1980 from several spacecraft [irradiance] 1400 from 10Be in ice cores 30, 000 yrs BP from 14C in tree rings (J Beer)

36 amazing observations from space
CONCLUSIONS Solar Physics - golden age - observations Magnetic theory playing a key role Sense of vitality will continue amazing observations from space (SOHO, TRACE, RHESSI, Hinode, Stereo, SDO, Orbiter) - bright new young students

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