Our Amazing Sun by Serendipity1

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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
     throne
     King & bride
- rays of Aten sun-disk
       protecting
   & giving them life
         Why Study the Sun ?
 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
        “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:
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
2. STRUCTURE of SUN   Vital
                    Statistics
                                       Radius =

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


Ball of gas held together by gravity
            Overall Structure
                                      Interior:
                                        Core

                                     Convection
                                       zone
                                      (> 0.7 R0)




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

 Thomas
  Harriot
discovered
   (1610)
w. telescope
 [Galileo]



-- Greeks,
 Chinese
Surprise (1908):

site of strong
magnetic field
Dark because cool
 But why cool ?

   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"
                    Movie

Intense magnetic
fields over whole
       Sun                  Movie

  B carried to
    edges of
convection cells
Chromosphere -- very dynamic
Simulation [Hansteen&Carlsson]


                                  Corona

                                  t. region
    Movie                             1
                                 Chromor
                                      1

                                  Photor
                                  light/
                                  dense.
4. CORONA ("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 !!!!
            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:
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)




             creates intricate
B strong - -dominates plasma structure
5. SOHO (Solar & Heliospheric Observatory)



            QuickTime™ an d a
                                             Launched 1995.
          Cinepak decompre ssor
      are need ed to see this p icture .       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
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
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

								
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