1. OUR AMAZING SUN
(Alexandria, March 26, 2006)
Eric Priest

2. For centuries we have worshipped the Sun
INTRODUCTION
For centuries we have worshipped the Sun

3. Ra or Re - the Sun god (old kingdom)
Ancient Egyptians
Many forms of Sun worship:
Ra or Re - the Sun god (old kingdom)

4. - the visible disk or face of the Sun
Aten
- the visible disk or face of the Sun

5. reflects solar energy, reason & mathematics
Eye of Ra or Horus
(-- eclipse)
reflects solar energy, reason & mathematics

6. Tutankhamun’s throne King & bride rays of Aten sun-disk protecting
& giving them life

7. Why Study the Sun ? So Sun is 1 of liveliest branches of astronomy
1. Of great scientific interest in own right
2. Influence on Earth
3. Important for Astronomy
-- fundamental cosmic processes
But -- Many basic properties still a mystery
So Sun is 1 of liveliest branches of astronomy

8. Traditionally close link Mathematics - Astronomy
To construct pyramids, Egyptians had outstanding grasp of both
e.g., Gregory Chair of Maths: James Gregory
( )
Invented Reflecting Telescope
Co-founder of Calculus

9. James Gregory Elected FRS (Academician) 1668 (age 30)
Appointed 1st regius prof maths at St Andrews (1668)
Given hall as lab -- see line for telescope along meridian

10. (Theme: Sun full of surprises)
“OUR AMAZING SUN”
(Theme: Sun full of surprises)
CONTENT:
1. Introduction Structure of the Sun Sunspots
4. Corona
5. Modern Surprises - SOHO satellite
* Solar Flares and CME's
Conclusions

11. Another Theme: B exerts force on plasma -- stores energy
Many surprises caused by magnetic field (B)
Sun is plasma --> coupled (intimate, subtle) to B
B exerts force on plasma -- stores energy

12. MOST of UNIVERSE is PLASMA:
Ionosphere --> Sun (8 light mins)
stars (4 light years)
[At 186,000 miles per sec]

13. MOST of UNIVERSE is PLASMA:
Ionosphere --> Sun (8 light mins)
Learn basic behaviour of plasma from Sun

14. Vital Statistics 2. STRUCTURE of SUN Radius =
100 x Earth = 700 Mm (1Mm = 1000 km)
Ball of gas held together by gravity

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

16. Covered with turbulent convection cells: “Granulation” (1 Mm)
Best ever images
Photosphere
Movie
Zoom from full disk
Movie
Covered with turbulent convection cells: “Granulation” (1 Mm)
by factor 100
to 70 km
resolution

17. Thomas Harriot discovered (1610) w. telescope [Galileo]
3. SUNSPOTS
Thomas Harriot discovered (1610) w. telescope [Galileo]
-- Greeks, Chinese

18. site of strong magnetic field
Surprise (1908):
site of strong magnetic field
Dark because cool But why cool ?
Because magnetic field (B) stops granulation

19. Penumbral structure created by B
Stunning Image
Penumbral structure created by B
[Scharmer & van der Voort]

20. Map of Photospheric Magnetic Field
White -- towards
Black -- away
Around sunspots --
bipolar
"Active Regions"

21. Movie B carried to edges of convection cells
Intense magnetic fields over whole Sun
Movie
B carried to edges of convection cells

22. Chromosphere -- very dynamic
Simulation [Hansteen&Carlsson]
Corona
t. region
Movie
Chromor
Photor
light/
dense.

23. Faint open structures -- Bright closed structures
("crown") -- See at ECLIPSE of Sun
4. CORONA
Faint open structures -- Bright closed structures
SURPRISE (1868) -- Light from new element "Helium"
SURPRISE (1940) -- Temperature is million degrees !!!!

24. In corona B dominates plasma
Another ECLIPSE
Structure created by B
In corona B dominates plasma
& heats plasma

25. Eclipse path

26. Iran 1999 (Koutchmy -- see tomorrow)
Radial structures: outflow --solar wind
Research students imaginative:

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

28. Picture with X-ray telescope:
Leon Golub (tomorrow) - pioneer
Image from latest new satellite:

29. Close-up of Magnetic Loops (Active region)

30. From the Side in Corona (TRACE)
B strong
- creates intricate structure
- dominates plasma

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

32. The SUN this week
Photo sphere

33. Magnetic Field

34. Corona at 1.6 MK

35. Corona at 2.0 MK

36. QN. -- ? How Do Flares & CME’s Occur
SOHO Coronagraph -- Artificial eclipse
Discovered huge ejections of plasma
[Can reach Earth - communications / satellites]

37. On October 28, 2003
Photo- sphere
[from SOHO]
3rd largest flare

38. Outer Corona [from SOHO]
CME 2000 km/s
(5 times faster than normal)
Snow -- relc particles

39. Thurs
Aurora in St Andrews

40. 1 Week Later (Nov 4 )- Fireworks Continued
the biggest solar flare ever recorded !

41. Close-up from TRACE
Movie of flare at limb
Movie of zoom in and out

42. 6. CONCLUSIONS Ancient egyptians intrigued by Sun -- continues
Solar Physics - golden age - space observations
Sense of vitality will continue

43. Future Space Missions * Two satellites Stereo images of corona
STEREO July 2006
* Two satellites
Stereo images of corona
Solar B (Japan-US-UK) Sept * Connections surface/corona
Solar Dynamics Observatory 2008
* Successor to SOHO
Solar Orbiter (ESA) 2015
* 3 times closer than Mercury