FROM SUN TO EARTH 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
Our Sun is a turbulent, active star that can have dramatic effects on the Earth and other planets
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.
The Sun is the only star known to grow vegetables. (Dr.Philip Scherrer, Stanford University) 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(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.)
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 Size of Earth, for comparison Like fudge or oatmeal cooking, the Sun’s surface boils up with heat, then crashes down
As the Sun turns Like the Earth, the Sun rotates. However, unlike the Earth, the Sun has a complex rotation mechanism.
1 2 3 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? Helioseismology is the technique of studying low frequency, primarily sound, waves to probe the inside of the Sun, Acoustic waves “bouncing around” in the solar interior. Sun-quake observed
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 The amount of magnetic activity on the Sun varies in an 11 year cycle. A regular cycle of sunspot numbers over the past 300 years.
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 June 12, 2000 Jan 7, 2004
Solar Eruptions Common during the Sun’s active periods Huge flare of 28 October 2003 Solar prominence dwarfs Earth in size
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 Chart (2 channel) from 2-5 November 2003 shows 4 X-class and many B, C, and M class flares Category X28 flare, largest ever recorded, erupts on November 4, 2003
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.
Beyond the Sun The Sun’s corona, or atmosphere, is visible during a solar eclipse.
Special telescopes can study the corona by creating an artificial solar eclipse. Quiet Sun Active Sun 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 Sun generates Space Weather in our solar system Solar activity can have a dramatic impact on communications, satellites, and astronauts.
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 www.solarstorms.org solar.sec.noaa.gov www.exploratorium.edu/spaceweather www.spaceweathercenter.org www.spaceweather.com