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

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

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

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

OUR AMAZING SUN(Alexandria, March 26, 2006)

Eric Priest

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1. INTRODUCTION

For centuries we have worshipped the Sun

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Ancient Egyptians

Many forms of Sun worship:

Ra or Re - the Sun god (old kingdom)

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Aten

- the visible disk or face of the Sun

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Eye of Ra or Horus

(-- eclipse) reflects solar energy,

reason & mathematics

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Tutankhamun’s

throneKing & bride

- rays of Aten sun-disk protecting

& giving them life

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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

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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

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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

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“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

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Sun is plasma --> coupled (intimate,

subtle) to B

Another Theme:Many surprises caused by magnetic field (B)

B exerts force on plasma -- stores energy

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Ionosphere --> Sun (8 light mins)

stars (4 light years) [At 186,000 miles per sec]

MOST of UNIVERSE is PLASMA:

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Ionosphere --> Sun (8 light mins)

Learn basic behaviour of plasma from Sun

MOST of UNIVERSE is PLASMA:

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Vital Statistics

Ball of gas held together by gravity

100 x Earth = 700 Mm (1Mm = 1000 km)

2. STRUCTURE of SUN

Radius =

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Interior:Core

Convection zone

(> 0.7 R0)

Atmosphere: Photosphere, Chromosphere, Corona

Overall Structure

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Best ever images

by factor 100

to 70 km

resolution

Zoom from

full diskMovie

Covered with turbulent

convection cells: “Granulation”

(1 Mm)

Photosphere

Movie

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Thomas Harriot

discovered (1610) w. telescope

[Galileo]

-- Greeks, Chinese

3. SUNSPOTS

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Dark because cool But why cool ?

Surprise (1908):

site of strong magnetic field

Because magnetic field

(B) stops granulation

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Stunning Image

Penumbral structure

created by B

[Scharmer & van der Voort]

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Map of Photospheric Magnetic Field

White -- towards

Black -- away

Around sunspots -- bipolar

"Active Regions"

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Intense magnetic fields over whole

Sun

Movie

B carried to edges of

convection cells

Movie

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Chromosphere -- very dynamic

Simulation [Hansteen&Carlsson]

Corona

Chromor

Photor

light/dense.

β <1

β >1

t. regionMovie

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("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

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Another ECLIPSE

In corona B

dominates plasma

& heats plasma

Structure created by B

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Eclipse path

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Iran 1999(Koutchmy

-- see tomorrow)

Radial structures: outflow --solar wind

Research students

imaginative:

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Normally need eclipse to see -- Glare of surface

Observe direct with X-ray telescope

As T increases (furnace), object becomes bluer

CORONA:

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Picture with X-ray telescope:

Image from latest new satellite:Leon Golub (tomorrow) - pioneer

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Close-up of Magnetic Loops (Active region)

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B strong - creates intricate structure

From the Side in Corona (TRACE)

- dominates plasma

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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.

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The SUN this

week

Photo sphere

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Magnetic Field

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Corona at 1.6 MK

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Corona at 2.0 MK

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QN. -- ? How Do Flares & CME’s Occur

SOHO Coronagraph -- Artificial eclipse

[Can reach Earth - communications / satellites]

Discovered huge ejections of plasma

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Photo- sphere

[from SOHO]

On October 28, 2003

3rd largest flare

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Outer Corona [from

SOHO]CME 2000

km/s

(5 times faster than

normal)

Snow -- relc

particles

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Thurs Aurora in St Andrews

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1 Week Later

(Nov 4 )- Fireworks Continued

the biggest

solar flare ever

recorded !

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Close-up from TRACE

Movie of flare at limb

Movie of zoom in and out

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6. CONCLUSIONS

Solar Physics - golden age - space observations

Sense of vitality will continue

Ancient egyptians intrigued by Sun -- continues

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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