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

throneKing & 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

(1638-1675)

Co-founder of Calculus

Invented Reflecting Telescope

Traditionallyclose 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 R0)

Atmosphere: Photosphere, Chromosphere, Corona

Overall Structure

Best ever images

by factor 100

to 70 km

resolution

Zoom from

full diskMovie

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

Chromor

Photor

light/dense.

β <1

β >1

t. regionMovie

("crown") -- See at ECLIPSE of Sun

Faint open structures -- Bright closed structuresSURPRISE (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 1995. Orbiting Sun

in phase with Earth

MANY NEW SURPRISES

--> 1st comprehensive view of Sun

QuickTime™ and aCinepak decompressor

are needed to see this picture.

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, 2003

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

Solar Physics - golden age - space observations

Sense of vitality will continue

Ancient egyptians intrigued by Sun -- continues

Future Space Missions

STEREO July 2006* Two satellitesStereo 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