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