Anatomy of the Sun
Layers: Core – where fusion occurs Radiation Zone Convection Zone Sun’s Atmosphere
Photosphere – visible surface of sun, innermost layer sun’s atmosphere (5800K) Chromosphere – 10,000K, such high temperatures cause H2 to emit a reddish light. Only visible when photosphere is obscured as in an eclipse Corona – outer layer, 1,000,000 K, flares extend out millions of KM Sun’s Magnetic Field
particles are constantly boiling off the Sun and streaming outward at very high speeds = solar wind Solar wind is always pushing on the Earth's magnetic field (magnetosphere), changing its shape. Note: Compressed on the day side, and forms a tail the night side The Aurora What makes the Aurora Happen? 1. The atmosphere is made up of mostly the gases
N2 and O2, with traces of H2, He and various compounds. 2. The Earth has a magnetic field. (lines closest together = strongest field furthest apart = weakest.) 3. Charged Particles There are always electrons and positive ions traveling along the Earth’s magnetic field as if they were wires. These charged particles are the "ammunition" of an aurora. The Big Push (Do not write this slide)
Build-up of pressure from the solar wind creates an electric voltage The voltage pushes electrons (which are very light) toward the magnetic poles, until huge numbers of electrons are pushed into the ionosphere. (Do not write this slide) In the ionosphere, the speeding electrons collide violently with gas atoms causing them to release both light and more electrons. The electrons flowing back out don't have as much energy as the speedy incoming ones had… Why? The energy was transferred into light to make the aurora The Big Push (write this summary) Electrically charged particles (mostly electrons) accelerate along the magnetic field lines into the ionosphere, where they collide with gas atoms, causing the atoms to give off light. What is the Solar connection? (do not write this slide) We know that the solar wind is the power source for auroras. There is a connection between activity on the Sun and auroral activity on the earth. (do not write this slide) The Sun and its wind are constantly changing. The flow of particles and the intensity of the solar wind's magnetic field increase when the Sun is more active. High Energy Solar Events: Coronal mass ejections (CME's) Solar flares - parts of the Sun's outer atmosphere practically explode, producing huge bursts of solar wind High-energy solar events can result in very large and unusual auroras. Solar flares vary, from several per day to less than one each week. Solar activity varies with an 11-year cycle (the solar cycle). Peak Solar activity = more sunspots = more solar flares = more energized particles in the magnetosphere =increased aurora activity. Where can you see them?