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

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

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

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

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

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

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

Traditionally close link Mathematics - Astronomy To construct pyramids, Egyptians had outstanding grasp of both e.g., Gregory Chair of Maths: James Gregory (1638-1675) Invented Reflecting Telescope Co-founder of Calculus

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

(Theme: Sun full of surprises) “OUR AMAZING SUN” (Theme: Sun full of surprises) CONTENT: 1. Introduction 2. Structure of the Sun 3. Sunspots 4. Corona 5. Modern Surprises - SOHO satellite * Solar Flares and CME's Conclusions

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

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

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

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

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

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

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

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

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

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

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

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

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 !!!!

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

Eclipse path

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

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

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

Close-up of Magnetic Loops (Active region)

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

5. SOHO (Solar & Heliospheric Observatory) Launched 1995. Orbiting Sun in phase with Earth Observing Sun continuously for 1st time (ESA/NASA) --> 1st comprehensive view of Sun MANY NEW SURPRISES

The SUN this week Photo sphere

Magnetic Field

Corona at 1.6 MK

Corona at 2.0 MK

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

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

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

Thurs Aurora in St Andrews

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

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

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

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