Dr. Laura Peticolas

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2009 International Year of Astronomy The
Sun-Earth Connection
Dr. Laura Peticolas Space Sciences
Laboratory University of California at Berkeley
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Tonights main talking points

• We learn about our connection to the Sun through
  careful observations.
• Tools (such as telescopes, satellites, computers)
  help us to understand this connection.
• The Sun emits light of many different colors
  (wavelengths/frequencies) known as the
  electromagnetic spectrum.

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Tonights main talking points

• The Sun is a magnetic and dynamic star, ever
  changing in its output of light and particles.
• Earth is a giant electromagnet.
• The northern and southern lights (auroras) are
  global, dynamic glowing light displays
  originating at the boundary between Earths
  atmosphere and space.
• The Suns particles affect the magnetic field
  surrounding Earth in a dynamic way.

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1600sBirth of the Telescope

• Telescopes increased the ability of people to
  see details in astronomical objects such as the
  moons around Jupiter and spots on the Sun.

Johannes Hevelius observing with one of his
telescopes (from galileo.rice.edu)
Galileos telescopes (from galileo.rice.edu)
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Sunspots Observations

• In 1612 during the summer months, Galileo made a
  series of sunspot observations which were
  published in Istoria e Dimostrazioni Intorno Alle
  Macchie Solari e Loro Accidenti Rome (History and
  Demonstrations Concerning Sunspots and their
  Properties, published 1613).

Galileos sunspot drawing (from galileo.rice.edu)
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Sunspots Observations
Because these observations were made at
approximately the same time of day, the motion of
the spots across the Sun can easily be
seen. Conclusion the Sun rotates on its axis.
Movie made from Galileos sunspot drawings from
June 2, 1613 July 8, 1613 (from
galileo.rice.edu)
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Sunspots A modern understanding

• Sunspots are about 2,000 degrees Kelvin cooler
  than the average temperature on the photosphere
  (5,000 degrees Kelvin).
• They are bright but appear to be dark only in
  comparison to their very bright surroundings.
• Following long-lived sunspots through time
  allows one to determine the rotation rate of the
  Sun (25-36 days).
• The Sun spins faster at the equator (25 days)
  than at the poles (36 days).

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What is the Sun?
The Sun is a Star, but seen close-up. The Stars
are other Suns but very far away.
Stars, including the Sun, are giant balls of very
hot, mostly ionized gas that shine under their
own power (from nuclear fusion).
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Modern Solar Science Careful Observations
In 2006 NASA launched the STEREO (Solar
Terrestrial Relations Observatory) spacecraft to
continue our study of the Sun in ways not
possible on Earth. To understand why the
scientific instruments (tools) on the spacecraft
needed to be above Earths atmosphere and
magnetic field, we need a little more background.
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Light Careful Observations

• 1666 A.D. Sir Isaac Newton used a prism to show
  that white light from the Sun disperses to form a
  series of colors called the spectrum

Prism with white light shining through the prism,
shown at the top of the image, and the rainbow of
colors (spectrum) coming out of the prism, shown
at the bottom of the image.
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Electromagnetic Spectrum
1800 A.D. Fredrick W. Herschel used a prism and
thermometers to measure the temperature of each
color of light. During this experiment he placed
a thermometer to one side of the spectrum and
discovered infrared light.
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The Multiwavelength Sun
Looking at the Sun in different wavelengths of
light reveals different parts of the Sun with
different temperatures.
2 bright spots Fe XII Extreme Ultraviolet light
Wavelength 19.5 nm T 1.5 million K
2 dark spots Visible light (white light)
Wavelength 400-700 nm T 5,800 K
2 bright spots He II Extreme Ultraviolet light
Wavelength 30.4 nm T 60,000-80,000 K
2 bright spots Fe IX, X Extreme Ultraviolet
light Wavelength 17.1 nm T 1 million K
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The Multiwavelength Sun
The Extreme Ultraviolet Light (EUV light) is
blocked by our atmosphere we have to go to
space to get these images.
2 bright spots Fe XII Extreme Ultraviolet light
Wavelength 19.5 nm T 1.5 million K
2 dark spots Visible light (white light)
Wavelength 400-700 nm T 5,800 K
Space-based image (STEREO)
Earth-based image
2 bright spots He II Extreme Ultraviolet light
Wavelength 30.4 nm T 60,000-80,000 K
2 bright spots Fe IX, X Extreme Ultraviolet
light Wavelength 17.1 nm T 1 million K
Space-based image (STEREO)
Space-based image (STEREO)
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Observations of the Sun
Images from NASA TRACE
Zoom in images of the Sun in ultraviolet light
reveal loops of hot ionized gas (plasma) trapped
in magnetic fields above the locations of
Sunspots.
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The Magnetic Sun
Above Magnetic field tracing above sunspots on
the visible Sun.
Left Magnetic field tracing using a compass
around two magnetic poles
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STEREO Views June 2007
http//stereo-ssc.nascom.nasa.gov
STEREO camera B
STEREO camera A
STEREO Viewing geometry.
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The Sun in 3D
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STEREO Views April 2009
http//stereo-ssc.nascom.nasa.gov
SOHO camera
STEREO camera B
STEREO camera A
Now we can study the sides of the Sun we cannot
normally take images of.
STEREO Viewing geometry. SOHO is located near
Earth between Earth and the Sun (i.e. looking
straight to the Sun from Earth)
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Atmosphere of the Sun
During a total eclipse of the Sun, the very
bright Photosphere is blocked and the Suns outer
atmosphere becomes visible (in white light). We
call it the Corona.
Spacecraft, like SOHO and STEREO, place a disk in
front of their cameras to create an eclipse. They
are then able to take images with a larger view
of the Suns Corona. It extends far out into the
Solar System, in fact we live in it!
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Solar Flares CMEs
Coronal Mass Ejections (CMEs) are literally
ejections of mass from the Suns corona. CMEs
occur when large-scale magnetic fields break
and release energy and enormous amounts of matter
into space.
Solar flares are enormous explosions in the
atmosphere of the Sun. They release energy in
the form of light, heat, and the movement of
large amounts of plasma.
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STEREO CMEs new!
Coronal Mass Ejections (CMEs) are literally
ejections of mass from the Suns corona. CMEs
occur when large-scale magnetic fields break
and release energy and enormous amounts of matter
into space.
CME continues into the solar system
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The Solar Wind
The solar wind is a stream of mostly charged
particles that emanate from the Sun and blow
throughout the Solar System. The Suns Magnetic
field flows with these particles.
We have turned the data from these charged
particles and magnetic fields into sounds and put
the sounds with a movie of the outermost
atmosphere of the Sun from STEREO. We are
watching the Suns outer atmosphere from far away
while listening to the solar wind data nearby the
spacecraft. Find out more here http//cse.ssl.berk
eley.edu/impact/sounds.html
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Earth
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Earths Magnetic Field Careful Observations

• In the late 1500's, William Gilbert realized
  that the compass was a tiny magnet and it was
  interacting with a larger magnetic field in order
  to point north.
• In 1600, he published "De Magnete" explaining
  that "the globe of the earth is magnetic, a
  magnet," Chapter 17, Book 1.

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Satellite observations Earths Magnetosphere
The solar wind is electrically and magnetically
connected to Earths magneto-sphere
Satellite data (from sophisticated compasses and
particle detectors) out into space compared with
computer models gives us this model for Earths
Magnetosphere.
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Aurora Observations in 1800s
The aurora--a woodcut by Fridtjof Nansen
(1861-1930) (from www.phy6.org)
La Recherche Expedition, 1838-1840
(woolgathersome.blogspot.com)
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August 28, 1859

• Galveston, Texas
• August 28 as early as twilight closed, the
  northern sky was reddish, and at times lighter
  than other portions of the heavens. At 730 PM a
  few streamers showed themselves. Soon the whole
  sky from Ursa Major to the zodiac in the east was
  occupied by the streams or spiral columns that
  rose from the horizon. Spread over the same
  extent was an exquisite roseate tint which faded
  and returned. Stately columns of light reaching
  up about 45 degrees above the horizon moved
  westward. There were frequent flashes of
  lightning along the whole extent of the aurora.
  At 900 PM the whole of the streaking had faded
  leaving only a sort of twilight over the northern
  sky.

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Observations from Space
North Oval

• Aurorae are found in an oval around the North
  and South Magnetic Poles.
• These ovals are always present.

South Oval
Images on the left are from the IMAGE
satellite in 2001 and 2004 (UV Light) with
continents drawn on image.
Cusp Aurora
Image on the right is from the Polar Satellite,
2001 (UV Light.)
Both Ovals
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Aurora observed in 2008 from the ground (aurora
oval detail)
THEMIS All-sky camera mosaic image of aurora
across the Northern American Continent. The
cameras looking up using cameras with a wide
field-of-view.
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Sun-Earth Connection (1128 A.D.)

• In 2001, Astronomers drew a link between the
  earliest known record of sunspots, drawn by John
  of Worcester in England in AD 1128, and the
  aurora borealis (northern lights) recorded in
  Korea five days later.

http//www.abc.net.au/science/articles/2001/07/18/
330954.htm
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Space Weather Effects

• Energy from Solar Flares and CMEs can damage
  satellites and change orbits.
• Disrupt radio communications
• CME particles traveling near the speed of light
  threaten Astronauts.
• CMEs can intensify auroras (Northern and
  Southern Lights)
• Electric currents from intense aurora can cause
  power surges and blackouts.
• Electric currents from intense aurora create
  interesting magnetic field variations detectable
  on Earth.

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THEMIS with 5 satellites and many ground-based
stations, will learn more about dynamic aurora
and the magnetosphere.
Current Disruption Model 1. Substorms start in
the Current Disruption Region 2. Aurora are
triggered on Earth Effects then propagate
tailward 3. Reconnection is triggered
Magnetic Reconnection Model 1. Magnetic storm
starts at 20 Earth Radii 2. Effects propagate
to Current Disruption Region 3. Substorms and
aurora are triggered
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Magnetic Reconnection Model confirmed for one
case in 2008

• When a CME passes Earth, it can drag the
  magnetic tail far out into space.
• Stretched magnetic lines can break and then
  reconnect into a different shape.
• Electrons, guided by the magnetic field, speed up
  towards Earth and enhance auroras.

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New Postcard/Mini-poster THEMIS Unlocking the
Magnetic Mysteries of the Northern LightsNow
available -- a beautiful new XL THEMIS postcard
(6x9"). The front has a gorgeous photo of a vivid
green and purple aurora swirling above dark
trees. The back has text explaining a brief
history of our understanding of aurora, of what
still remains a mystery, and what the THEMIS
mission is doing to resolve these questions.
Highlighted are the most recent discoveries of
the timing of events that occurred in Earths
magnetosphere and triggered an auroral substorm
when the aurora changes rapidly from a tranquil
green glowing band to wildly dancing colorful
curtains of light. We hope the postcard will
inspire students, teachers and the public to
wonder and learn more about auroras, Earths
magnetosphere, and the THEMIS mission. Layout
and Design Laura Peticolas and Karin HauckText
Laura Peticolas, Karin HauckScience content
David Sibeck, Mark Moldwin, Sabine Frey, Bryan
MendezAurora photo Jan CurtisTHEMIS goddess
sketch Darlene YanSatellite artist rendition
GSFC Visualizations Lab
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Back-up slides
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The Different Parts of the Sun

• Core
• Nuclear Fusion H ? He
• T 15,000,000 K

• Radiative Zone
• Energy transported by light
• T 10,000,000 K

• Convective Zone
• Energy transported by convection

• Photosphere
• Visible surface
• Far less dense than Earths atmosphere
• T 5,800 K
• Sunspots T 4,000 K

• Chromosphere
• Thin layer above photosphere
• Produces most of Suns UV light
• T 10,000 K

• Corona
• Tenuous, extends out millions of kilometers
• Emits X-rays
• T 1,000,000 K

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The Solar Cycle
The number of Sunspots and solar flares increase
and decrease on an 11-year cycle.
The Suns magnetic field becomes more and more
twisted and complex from differential rotation.
It finally breaks and flips every 11 years. So
the total cycle is really 22 years from start to
finish.
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Causes of the aurora

• Electrons collide into the upper atmosphere,
  ionizing the gas, creating more electrons.
• All the electrons cause the gas to glow like neon
  lights or a plasma ball.
• 100 km (60 miles) above Earths surface.

Red Green Oxygen Pink/white (Blue Red)
Nitrogen
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Aurora Careful Observations
A map of the frequency with which auroras are
seen, produced in 1881 by the German scientist
Hermann Fritz (1830-1883) Thickest ring aurora
seen 100 times per year (www.phy6.org)