our amazing sun (alexandria, march 26, 2006) eric priest
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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
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