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Title: The Sun through the Eyes of SOHO: New Insight into our Star, and its Impact on the Earth


1
The Sun through the Eyes of SOHO New
Insight into our Star, and its Impact on the
Earths Environment
2
The Sun
  • The Sun is located in a spiral arm of our Galaxy,
    in the so-called Orionis arm, some 30,000
    light-years from the center.
  • The Sun orbits the center of the Milky Way in
    about 225 million years. Thus, the solar system
    has a velocity of 230 km/s (or 830 000 km/h)
  • Our galaxy consists of about 100 billion other
    stars and there are about 100 billion other
    galaxies
  • The Sun has inspired mythology in many cultures
    including the ancient Egyptians, the Aztecs, the
    Native Americans, and the Chinese.
  • The Sun is 333,400 times more massive than the
    Earth and contains 99.86 of the mass if the
    entire solar system
  • It consist of 78 Hydrogen, 20 Helium and 2 of
    other elements
  • Total energy radiated 100 billion tons of TNT
    per second

3
The Suns Structure
  • Core
  • Where the energy is created.
  • Nuclear reactions burn every second about 700
    million tons of hydrogen into helium.
  • Radiation Zone
  • Where energy is transported by radiation.
  • Although the photons travel at the speed of
    light, they bounce so many times through the
    dense material that they use about a million
    years to escape the Sun.
  • Convection Zone
  • Energy transported by convection (just like
    boiling soup) where heat is transported to the
    photosphere.

4
Sunspots
  • Dark areas (umbra, penumbra)
  • Strong magnetic fields
  • Inhibit energy transport from solar interior
  • Cooler areas, and therefore darker
  • Frequency varies with the 11-year solar cycle

Light and dark in this magnetic scan of the Sun
indicate concentrated areas of intense magnetic
field lines.
Close-up of sunspots
5
The Suns Magnetic Field
  • The Sun is strongly affected by magnetic forces.
  • The red arrows show open magnetic field lines
    emerging from the poles.
  • The gray arrows represent solar wind particles
    which carry field lines with it.
  • The bright active regions have closed magnetic
    field lines (orange).

6
Solar Cycle
Maunder minimum
7
Solar Activity 1992-1999
1992
1999
Yohkoh Soft X-ray
Kitt Peak magnetograms
8
The Solar Corona
  • The corona is the area just above the surface.
    While the surface is about 5,000o Celsius, the
    temperature in the corona reaches about 2 million
    degrees Celsius. What causes this rapid increase
    in tempera-ture is still one of the big mysteries
    in solar physics.

5,000 o C
2,000,000 o C
Corona
Solar interior
Surface
The black circle divides two images.
9
What is the Solar Wind?
  • A constant stream of particles flows from the
    Suns corona, with a temperature of about a
    million degrees and with a velocity of about 450
    km/s. The solar wind reaches out beyond Pluto's
    orbit (about 5900 million kilometers). The
    drawing showshow it pushes onand shapes the
    Earths magnetosphere(the dotted line).

10
The SOHO Mission
  • Joint program between the European Space Agency
    (ESA) and NASA.
  • An industry team led by Matra Marconi Space built
    SOHO in Europe. Its instruments were provided by
    nine European and three U.S. Principle
    Investigators
  • ESA responsible for SOHOs procurement,
    integration, and testing
  • NASA provided launch and mission operations (at
    Goddard Space Flight Center)

Launch 2 December 1995
11
Science Objectives
  • Solar Interior What are its structure and
    dynamics?
  • Corona Why does it exist and how is it heated?
  • Solar Wind Where is it accelerated and how?

12
SOHO Operations
  • Unique Operations Mode
  • Live display of data on scientists
    workstations
  • Real-time commanding by scientists, directly from
    their workstations
  • Emphasis on Coordinated Observations
  • Internally - daily planning meetings at EOF
  • Externally - campaigns and collaborations
    coordination and data exchange over Internet

13
Helioseismology
  • The entire Sun vibrates from a complex pattern of
    acoustic waves
  • The Sun's acoustic waves bounce from one side of
    the Sun to the other, causing the Sun's surface
    to oscillate up and down
  • The sound waves are influenced by conditions
    inside the Sun
  • By observing these oscillations on the surface we
    can learn about the structure of the solar
    interior

Hear the Sun sing!
Sound waves speeded up 42,000 times
14
Solar Interior Structure
Rotation
Convection zone differential rotation Radiation
zone rotates almost as a rigid body
Sound speed
15
Surface Dynamics - Oscillations
16
Time-Distance Helioseismology
  • New technique which is primarily developing with
    SOHO/MDI data
  • First ever images of flows in the convection zone
    of a star
  • First images of the subsurface structure of
    sunspots
  • Can give us the first insight into how sunspots
    are formed

17
SOHO sees through the Sun
  • First images of active regions on the far side of
    the Sun, from applying a new technique, called
    two-skip far-side seismic holography, to high
    quality MDI data.
  • Acoustic waves speed up in areas of strong
    magnetic field (active regions)
  • The delay of the sound waves is about 12 sec in a
    total travel time of 6 hours

Solar farside helioseismic holographic geometry
the pupil for imaging a circular area on the far
side is an annulus on the near side.
Near side magnetic field strength one half solar
rotation before (March 16) and after (April 12)
the day of the holographic, farside image Note
evolution of southeastern (lower left) part of
active region between nearside views on March 16
and April 12. The farside image shows that this
had occurred by March 29.

18
The Pulse of the Suns Dynamo
Rotation rates near the bottom of the convection
zone (white line), the most likely location of
the solar dynamo action, change markedly over 6
months. Faster/slower rates are shown in
red/blue. Near the surface bands of faster (red)
and slower (green) rotation move toward the
equator
19
The Beauty of the Sun EIT He II 304 Å 27 July
1999
20
3 Weeks of EIT observations
Fe XII 195 Å (1.500.000 K) 17 May - 8 June
1998
IMAX movie SOLARMAX A 40-minute documentary that
tells the story of humankinds struggle to
understand the Sun. It takes the audience on an
incredible voyage from pre-history to the leading
edge of todays solar science. World premier in
summer 2000 in London, now playing in a theatre
near you!
21
loops, loops, loops ...
22
TRACE the new kid on the block
23
EUV Spectroscopy with SOHO
  • From studying the position, shape and intensity
    of spectral lines we can derive physical
    properties of the emitting gas like
  • Temperature
  • Density
  • Flow velocities

24
Loop Dynamics / Active Region Flows
25
Heating of the CoronaThe Magnetic Carpet
Constant magnetic flux emergence, fragmentation
and disappearance T ? 40 hours
Each one of these loops carries as much energy as
a large hydroelectric plant would generate in 1
million years
26
The Temperature of the Corona
Line widths or Thermal Velocities OV width
exceeds 500 km/s which implies extremely high
kinetic temperatures T gt 200 MK at 3.5 solar
radii This behaviour of preferential heating -
cold electrons (derived from SUMER obs) - hot
protons - superhot heavy ions is consistent with
wave heating via ion cyclotron resonance
27
Acceleration of the Fast Solar Wind
Acceleration of the fast solar wind
Outflow velocities of protons and minor ions are
different! Acceleration takes place very low in
the corona O VI ions reach velocities of more
than 300 km/s below 2.5 solar radii
28
Source Regions of the High Speed Solar Wind
Observations with SUMER (UV Spectrometer)
  • SUMER spectroscopic observations in a coronal
    hole in Ne VIII 770Å (650 000 K)
  • Shows outflows (blue shifts) in coronal hole as
    compared to red shifts in quiet Sun
  • Largest outflows occur along the boundaries and
    the intersections of the chromospheric network
    (superimposed dark lanes)
  • solar wind breaking through network like grass
    around the edges of paving stones in a patio

Dopplergram showing the up- and downflows
Artists impression
29
Elemental and Isotopic Composition of the
Solar Wind
RED New elements/isotopes Green Rarely
observed Black Routinely observed
CELIAS has doubled the number of elements and
isotopes previously recorded in the solar wind
30
Eruptive Prominences
31
Eruptive Prominences
The Sun comes up with a great idea a light bulb
CME!
32
The many faces of CMEs
33
Coronal Moreton Waves
  • Speeds 200 - 600 km/s
  • Deflected by AR
  • Stop at CH boundaries
  • Usually associated with CMEs
  • Fast-mode Alfvén shock (cf. Uchida 1968, 1973)

34
Solar Flares
Sun-quake observed with SOHO/MDI
Flare observed with TRACE
35
Comets observed with SOHO/LASCO(over 290 comets
discovered so far!)
36
Comet Discoveries
  • As of 5 Feb 2001, SOHO discovered a total of 293
    comets (LASCO 292, SWAN 1)
  • Almost 25 of all comets dicoveries since 1760
    come from SOHO.
  • More than 85 of the comet discoveries during the
    past two years come from the SOHO and LINEAR
    programs.
  • Studies on dust-production of sungrazers
  • tails straight and narrow
  • no evidence for Lorentz force on charged dust
  • tails include a major population of
    sub-micron-sized dielectric grains (most probably
    silicates)

Beginning of NEO surveys
37
UV Spectroscopy of a Sungrazing
CometComet C/2001 C2 (SOHO-294)
  • Discovered in LASCO real-time images on Internet
    by two amateur astronomers
  • Sebastian Hoenig, Germany
  • Xing Ming Zhou, China)
  • Outgassing rate ? 100 kg/s
  • Size of comet nucleus ? 10 m
  • Densities
  • 10,000 particles/cm3 at 4.82 R?
  • 86,000 particles/cm3 at 3.32 R?

38
Shadow of a Comet
SWAN maps the whole sky in UV light of H Ly-?. It
sees a huge cloud of interstellar hydrogen that
bathes the entire solar system and interacts with
the solar wind. Comets (dirty snowballs) are
surrounded by large hydrogen clouds
- water-ice vaporizes near Sun -
solar UV radiation splits up water molecules
- liberated hydrogen atoms glow in UV
light ? Absolute determination of amount
of hydrogen released by comet The hydrogen cloud
blocks out the UV radiation that normally
illuminates the sky ? comets UV
shadow. Hale-Bopps shadow more than 150 million
km long!
39
Looking at the Far Side of the Sun
40
SOHO Captures Planet Gathering
41
From Solar Min towards Solar Max
42
The Extended Corona
1996
1999
43
Solar Irradiance Measurements - The Sun as a
Star
  • VIRGO - Total solar irradiance
  • CDS EUV 307-380 Å and 515-632 Å spectral
    irradiance and 69 full disk images taken each
    month
  • SEM (CELIAS) EUV disk integrated flux from
    1-500Å and in 260-340 Å (He II 304 Å)

44
SOHO and CMEs To the Max?
CME rate is reaching the value historically found
at solar maximum, roughly one order of magnitude
higher than at minimum.
45
The 14 July 2000 Event
46
The 14 July 2000 Event
47
The 14 July 2000 Event
48
The 14 July 2000 Event
49
The Biggest Sunspot Group in 10 Years
  • AR 9393 developed a complex delta-gamma magnetic
    field configuration while rotating towards the
    center of the Sun
  • An X-flare and CME was observed on 29 March 2001
    causing a severe geomagnetic storm on Earth
  • Aurora was observed south in Europe

ALASKA (Zimmerman)
Nice (Benvenuto)
50
The Biggest Flare on Record
  • At 2151 UT, Monday 2 April 2001, active region
    9393 unleashed a major solar flare reclassified
    as at least an X20 It appears to be the biggest
    flare on record, most likely bigger than the one
    on 16 August 1989 and definitely more powerful
    that the famous 6 March 1989 flare which was
    related to the disruption of the power grids in
    Canada.

51
The Sun-Earth Connection
  • How and why does the Sun vary?
  • How does the Earth respond?
  • What are the impacts on humanity?

52
What is Space Weather?
  • SPACE WEATHER refers to conditions on the Sun and
    in the solar wind, magnetosphere, ionosphere, and
    thermosphere that can influence the performance
    and reliability of space born and ground-based
    technological systems and that can affect human
    life or health.
  • Space Weather effects on installations on Earth
    not a new phenomena
  • 17 November 1848 Telegraph wire between Pisa and
    Florence interrupted
  • September 1851 Telegraph wire in New England
    disrupted
  • Induced currents made it possible to run the
    telegraph lines without batteries. The following
    is a transcript between Portland and Boston
    (1859)
  • Portland Please cut off your battery, let
    us see if we can work with the auroral
    current alone
  • Boston I have already done so! How do
    you receive my writing?
  • Portland Very well indeed - much
    better that with batteries

53
Aurora Borealis
54
Effects from Solar Storms
Source Flares
CMEs/Flares CMEs/Coronal Holes
55
Navigation systems (GPS, LORAN C)
  • When the ionosphere between the satellites and
    the user becomes turbulent and irregular, the
    signal may scintillate and prove difficult to
    track
  • loss of signal lock on one or several satellites
  • Both single and dual frequency systems may be
    affected
  • The Total Electron Content (TEC) along the path
    of a GPS signal can introduce a positioning error
    ( up to 100 m)
  • The effects on GPS could be one of the most
    significant space weather effects due to the
    planned reliance of this system in the future.

A 7-10 km height change of the lower ionosphere
can give position errors of 1-12 km
56
Satellite Failures due to Space Weather Effects
  • Anomalies due to spacecraft surface and internal
    charging (Marecs, ECS, Meteosat, TELE-X,..)
  • Latch-up induced failures
    (ESR-1, PRARE,
    Equator-S,..)
  • SEUs in linear circuits(Anik 1 2)
  • Solar Array problems/degradation (Tempo,
    PanAm, ECS,.)
  • More recent satellite failures
  • Telestar 401 (Jan 11 1997)
  • TV links etc..
  • Galaxy IV (1998)
  • silenced 80 of pagers in North America
  • More than 12 satellites lost due to Space Weather
    Effects
  • Last 4 years space losses may have exceeded 500
    million
  • Commercial interests often do not allow anomaly
    reporting.

57
Geomagnetic Induced Currents
  • These currents will leak into all long
    conductors
  • power grids,
  • oil and gas pipelines (increased corrosion)
  • Train light signals can be affected (two
    documented events in Sweden)

58
Damage to Transformers
Damage to a transformer at a power plant
Delaware, New Jersey i march 1989. Price 10 mill
USD Repair can take up to 1 year. In this
particular case they were lucky to find a used
one from a shut down plant. Took only 6 weeks to
restore Sweden simultaneous power loss in six
130 kV power distribution lines Chicago Five
transformers in the Chicago area failed due to
elevated geomagnetic activity in April 94
59
High Energy Particles Hazards to Humans
  • Humans in space
  • Space Shuttle, International Space Station,
    missions to Mars
  • Crew/Passengers in high-flying jets
  • Concorde carries radiation detectors
  • Passengers may receive radiation doses equivalent
    to several chest X rays.

60
Space Weather Why should we care?
We did survive the last
solar max!
  • Our society are much more dependant on
    technology today compared to in 1989
  • The most rapidly growing sector of the
    communication market is satellite
    based
  • Broadcast TV/Radio,
  • Long-distance telephone service, Cell phones,
    Pagers
  • Internet, finance transactions
  • Change in technology
  • more sensitive payloads
  • high performance components
  • lightweight and low cost
  • Humans in Space
  • More and longer manned missions
  • Space Weather warning will be very
  • important for our society in the future.

61
Solar Cycles and Climate Variations
  • 11 years Schwabe
  • 22 years Magnetic cycle
  • 80-90 years Gleissberg
  • 180-210 years Seuss

62
The Sun and Global Warming
  • Long term variations in total irradiance (total
    energy)
  • Assumed to only explain part of the global
    warming
  • Long term variation in UV/EUV radiation
  • Changes in chemistry (ozone), temperature etc. in
    the Earths atmosphere. Could lead to climate
    changes
  • Long term variation in the Suns magnetic field
  • Modulates cosmic rays and the solar wind

1994
1991
63
Variations in the Solar Magnetic Flux
  • The solar magnetic flux has increased by a factor
    of 2.3 since 1901
  • The estimated long term changes in TSI alone can
    account for
  • 52 of the temperature rise between 1910-1960
  • 31 of the rise since 1970

64
Cosmic Rays and Clouds
  • Variations in the solar activity/magnetic field
    changes the amount of cosmic particles
    penetrating into the solar system (and the
    Earths atmosphere).
  • Strong correlation with cosmic ray flux and low
    clouds has been found
  • The global cloud cover is an important factor in
    climate forcing

65
Long term monitoring of the Sun
SOHO Solar Maximum Science
Programme
  • Why does the Sun Vary?
  • solar dynamo
  • atmosphere
  • heliosphere
  • How does solar variability affect life
    and society?
  • magnetosphere response
  • space weather forecast
  • How do the planet respond to solar
    Variations?
  • climate changes

66
GSFC June 25 1998 (0712 UT)
Prologue
The following E-mail was issued by the Flight
Operations Team at NASA/GSFC
After the planned momentum management, while
still in thruster mode, the Attitude and Orbital
Control Subsystem (AOCS) switched into
ESR (Emergency Sun Re-acquisition mode) on 24
June at 2316, due to a procedure problem. On 25
June at 0235 a second ESR occurred
during standard ESR recovery, triggered by roll
rate the reason is unclear. Some time later, at
0438, a third ESR triggered by a
fine Sun-pointing anomaly and all telemetry was
lost.
Our worst nightmare was
beginning to unfold SOHO WAS LOST IN
SPACE
67
The Drama of the Summer of 1998
68
We did it!
69
New features on the SOHO Web-pages
http//sohowww.estec.esa.nl/
  • SOHO Real-time display
  • http//sohowww.estec.esa.nl/data/realtime-images.h
    tml
  • Mpegs, Gif animations, Java, and individual
    frames for press/TV
  • A Java-based real time display has been developed
    to make it easy to set up a SOHO display at
    different locations around the world (E.g.
    Museums, ESA facilities etc..)
  • Requirement is a PC with internet connection and
    a web-browser
  • Written by Dennis Wang and Nathan Rich from the
    LASCO team (NRL).
  • SOHO Real-time Screen Saver (more the 250,000
    distinct users)
  • Hot Shots from SOHO

70
SOHO Interactive CD-ROM
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