The American Geophysical Union Space Physics and Aeronomy Section

The American Geophysical Union (AGU) Space 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 dramatic effects on the Earth and other planets Our Sun is a turbulent, active star

The 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? 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 Sun (just the facts) 150 million km from Earth 1.4 million km across = 109 Earths 4.5 billion years old 2x10 30 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? 1

The Sun appears white to us but it radiates in all wavelengths (visible and nonvisible “colors”) The electromagnetic spectrum

The 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 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 turns Like the Earth, the Sun rotates. However, unlike the Earth, the Sun has a complex rotation mechanism.

The 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)

How do we know about the interior of the Sun? Sun-quake observed Acoustic 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,

Sunspots Sunspots Sunspots denote regions of strong magnetic fields. They appear dark because they are relatively cooler than the surface.

Sunspots and Magnetic Fields Sunspots appear around regions of strong magnetic fields

How do magnetic fields cause solar activity? Most sunspots and events on the Sun are caused by eruptions and tangles of complex magnetic fields

Seeing Magnetic Field Lines Plasma emission traces out magnetic fields in the solar corona

What happens below a sunspot? New techniques allow us to study gas flow beneath a sunspot.

The 11 year sunspot 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 Sun Changes in solar activity after only 3 years

Dramatic changes occur during the solar cycle X-ray and magnetic activity compared

Sunspots appear at different latitudes throughout the solar cycle Jan 7, 2004 June 12, 2000

Solar Eruptions Solar prominence dwarfs Earth in size Huge flare of 28 October 2003 Common during the Sun’s active periods

Classifications of solar flare intensity Categories 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 2003 shows 4 X-class and many B, C, and M class flares

Explosions on the Sun (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 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. Beyond the Sun

Quiet Sun Active Sun Special telescopes can study the corona 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 the solar system and shapes Earth’s magnetosphere

The Earth’s magnetosphere is buffeted during a solar storm

The Sun generates Space Weather in our solar system Solar activity can have a dramatic impact on communications, satellites, and astronauts.

Solar activity causes colorful aurorae

Solar 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 Weather affects the Moon and other planets we hope to explore. Mars Aurorae on Neptune, Saturn, and Jupiter

The Ionosphere Solar storms affect the Earth’s ionosphere and interfere with communications.

Space Physics & Aeronomy Helpful Sites sohowww.nascom.nasa.gov sun.stanford.edu solar.sec.noaa.gov