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The American Geophysical UnionThe American Geophysical UnionSpace Physics and Aeronomy Space Physics and Aeronomy
SectionSection
The American Geophysical Union (AGU)The American Geophysical Union (AGU)Space Physics and Aeronomy (SPA) SectionSpace Physics and Aeronomy (SPA) Section
The American Geophysical Union (AGU)The American Geophysical Union (AGU)Space Physics and Aeronomy (SPA) SectionSpace Physics and Aeronomy (SPA) Section
Solar and heliospheric physics - the study of the Sun and solar variability together with the composition, structure, and dynamics of the interplanetary medium and its interaction with the local interstellar medium
Magnetospheric physics - the study of the plasmas, magnetic and electric fields, and current systems in the magnetospheres of the Earth and other planets.
Aeronomy - the study of the ionized and neutral upper atmospheres of the Earth and planets and of their interactions with their respective space environments
that can have that can have dramatic dramatic
effects on the effects on the Earth and Earth and
other planetsother planets
Our Sun is a turbulent, active starOur Sun is a turbulent, active star
The Sun’s place in the GalaxyThe Sun’s place in the GalaxyThe Sun’s place in the GalaxyThe Sun’s place in the Galaxy
The Sun is one of about 200 billion stars in a galaxy we call Milky Way. It resides on the outskirts, about 28,000 light years from the center.
Why Study the Sun?Why Study the Sun?Why Study the Sun?Why Study the Sun?
• Understand how the Sun affects the Earth and the solar system
• Understand how stars work
• Understand more about the laws of nature
The Sun is the only star known to grow vegetables.
(Dr.Philip Scherrer, Stanford University)
The SunThe Sun(just the facts)(just the facts)The SunThe Sun
(just the facts)(just the facts)
• 150 million km from Earth
• 1.4 million km across = 109 Earths
• 4.5 billion years old
• 2x1030 kg mass. (333,000 times the mass of the Earth)
• 75% hydrogen, 24% helium, 1% everything else
• Makes up 99.98% of the mass of the solar system
Surface: 5800 degrees K. (10,000 degrees F.) Core: 15.6 million K. (280,000 F.)
What color is the Sun?What color is the Sun?
1
The Sun appears white The Sun appears white to usto us
but it radiates in all wavelengths (visible and nonvisible “colors”)
The electromagnetic spectrum
The Sun from the Inside OutThe Sun from the Inside Out
Knowledge we gain about the Sun can be applied to other stars.
What makes the Sun hot?
Fusion in the Sun’s core produces heat/energy
The Sun’s Roiling SurfaceThe Sun’s Roiling Surface
Like fudge or oatmeal cooking, the Sun’s surface boils up with heat,
then crashes down
Size of Earth, for comparison
As the Sun turnsAs the Sun turns
Like the Earth, the Sun rotates. However, unlike the Earth, the Sun has a complex rotation mechanism.
The Sun’s Variable RotationThe Sun’s Variable RotationThe Sun’s Variable RotationThe Sun’s Variable Rotation
Solar Rotation Rates:
1) Polar regions = 36 days
2) 60 Degrees = 31 days
3) Equatorial Regions = 26 days
The Sun is a ball of gas. Different regions rotate at different speeds, both in the interior and on the surface, resulting in differential rotation.
The Earth is solid and rotates at one speed (~24 hrs/day).
1
2
3
How do we know about the How do we know about the interior of the Sun?interior of the Sun?
How do we know about the How do we know about the interior of the Sun?interior of the Sun?
Sun-quake observedAcoustic waves “bouncing around” in the solar interior.
Helioseismology is the technique of studying low frequency, primarily sound, waves to probe the inside of the Sun,
SunspotsSunspots SunspotsSunspots
Sunspots denote regions of strong
magnetic fields. They appear dark because
they are relatively cooler than the surface.
Sunspots and Magnetic FieldsSunspots and Magnetic FieldsSunspots and Magnetic FieldsSunspots and Magnetic Fields
Sunspots appear around regions of strong magnetic fields
How do magnetic fields How do magnetic fields cause solar activity?cause solar activity?
Most sunspots and events on the Sun are caused by eruptions and tangles of complex magnetic fields
Seeing Magnetic Field Seeing Magnetic Field LinesLines
Seeing Magnetic Field Seeing Magnetic Field LinesLines
Plasma emission traces out magnetic
fields in the solar corona
What happens below a sunspot?What happens below a sunspot?What happens below a sunspot?What happens below a sunspot?
New techniques allow us to study gas flow beneath a sunspot.
The 11 year The 11 year sunspot cyclesunspot cycleThe 11 year The 11 year
sunspot cyclesunspot cycle
A regular cycle of sunspot numbers over the past 300 years.
The amount of magnetic activity on the Sun varies
in an 11 year cycle.
Comparing the quiet and active SunComparing the quiet and active SunComparing the quiet and active SunComparing the quiet and active Sun
Changes in solar activity after only 3 years
Dramatic changes occur Dramatic changes occur during the solar cycleduring the solar cycle
X-ray and magnetic activity compared
Sunspots appear at different latitudes Sunspots appear at different latitudes
throughout the solar cyclethroughout the solar cycle Sunspots appear at different latitudes Sunspots appear at different latitudes
throughout the solar cyclethroughout the solar cycle
Jan 7, 2004
June 12, 2000
Solar EruptionsSolar Eruptions
Solar prominence dwarfs Earth in size
Huge flare of 28 October 2003
Common during the Sun’s active periods
Classifications of solar flare intensityClassifications of solar flare intensityClassifications of solar flare intensityClassifications of solar flare intensityCategories A & B -- Small
Category C -- larger but few noticeable consequences to Earth
Category M – Medium; cause radio blackouts that affect Earth’s polar regions
Category X – major events that can trigger planet-wide radio blackouts and severe radiation storms
Category X28 flare, largest ever recorded, erupts on November 4, 2003
Chart (2 channel) from 2-5 November 2003shows 4 X-class and many B, C, and M class flares
Explosions on the SunExplosions on the Sun(Coronal Mass Ejections)(Coronal Mass Ejections)Explosions on the SunExplosions on the Sun
(Coronal Mass Ejections)(Coronal Mass Ejections) A billion tons of hot gas being launched from the
Sun.
White circle in image indicates size and location of Sun, which is blocked by a metal disk in the instrument.
Source of Flares and Source of Flares and Coronal Mass Ejections?Coronal Mass Ejections?
Magnetic field lines poke through the solar surface, producing sunspots, flares, and coronal
mass ejections.
The Sun’s corona, or atmosphere, is visible during a solar eclipse.The Sun’s corona, or atmosphere, is visible during a solar eclipse.
Beyond the SunBeyond the Sun
Quiet Sun
Active Sun
Special telescopes can study the corona Special telescopes can study the corona by creating an artificial solar eclipse.by creating an artificial solar eclipse.
The white circle in the images indicates the size and position of the Sun.
A solar “wind” streams into A solar “wind” streams into the solar system and shapes the solar system and shapes
Earth’s magnetosphereEarth’s magnetosphere
A solar “wind” streams into A solar “wind” streams into the solar system and shapes the solar system and shapes
Earth’s magnetosphereEarth’s magnetosphere
The Earth’s magnetosphere is buffeted during a The Earth’s magnetosphere is buffeted during a solar stormsolar storm
The Earth’s magnetosphere is buffeted during a The Earth’s magnetosphere is buffeted during a solar stormsolar storm
The Sun generates The Sun generates Space Weather in our Space Weather in our
solar systemsolar system
The Sun generates The Sun generates Space Weather in our Space Weather in our
solar systemsolar system
Solar activity can have a dramatic impact on communications, satellites, and astronauts.
Solar activity causes Solar activity causes colorful auroraecolorful aurorae
Solar activity causes Solar activity causes colorful auroraecolorful aurorae
Solar storm causes blackout in 1989Solar storm causes blackout in 1989
In 90 seconds, 6 million people lost power for 9
hours.
An October 2003 solar storm knocked out the Mars Odyssey probe
Space WeatherSpace Weather affects the Moon affects the Moon and other planets and other planets we hope to explore.we hope to explore.
Mars
Aurorae on
Neptune, Saturn,
and Jupiter
The IonosphereThe IonosphereThe IonosphereThe Ionosphere
Solar storms affect the Earth’s ionosphere and interfere with communications.
Solar storms affect the Earth’s ionosphere and interfere with communications.
Space Physics & Space Physics & AeronomyAeronomy
Space Physics & Space Physics & AeronomyAeronomy
Helpful Sites
sohowww.nascom.nasa.gov
sun.stanford.edu
www.solarstorms.org
solar.sec.noaa.gov
www.exploratorium.edu/spaceweather
www.spaceweathercenter.org
www.spaceweather.com