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

1.INTRODUCTION For centuries we have worshipped the Sun

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

Aten - the visible disk or face of the Sun

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

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 Why Study the Sun ? So Sun is 1 of liveliest branches of astronomy

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

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

“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

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

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 MOST of UNIVERSE is PLASMA:

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

Interior: Core Convection zone (> 0.7 R 0 ) Atmosphere: Photosphere, Chromosphere, Corona Overall Structure

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

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

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

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"

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

Chromosphere -- very dynamic Simulation [Hansteen&Carlsson] Corona Chromo r Photo r light/ dense. t. region Movie

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

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

Eclipse path

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

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

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

Close-up of Magnetic Loops (Active region)

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

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

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 [Can reach Earth - communications / satellites] Discovered huge ejections of plasma

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

Outer Corona [from SOHO] CME 2000 km/s (5 times faster than normal) Snow -- rel c 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  Solar Physics - golden age - space observations  Sense of vitality will continue  Ancient egyptians intrigued by Sun -- continues

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