1. THE SUN Energy from the sun, in the form of sunlight supports all life via photosynthesis, and drives the Earth’s climate and weather.

2. THE SUN Began shining 5 billion years ago Expected to continue shining for 5 billion years more At the end of its life it will start to fuse helium into heavier elements becoming a red giant and engulfing the Earth. 73% hydrogen 25% helium Tiny fraction is other elements such as C, N, O, Ni, Fe etc. Over 100 x diameter of the earth

3. A close look at the Sun The sun is made of many layers –Core –Radiative and convective Zone –Photosphere –Chromosphere –Corona

4. The Core Where nuclear fusion occurs (light atoms fuse to become heavier ones) Temperatures and pressures are enormous Temperatures reach 15 million o C.

5. Radiative and Convective Zone Radiative –The plasma is very dense –Light takes approximately 100,000 years to pass through as it is constantly absorbed and re- emitted Convective – Bubbles of hot plasma circulate up toward the surface while cooler regions of plasma sink

6. The Photosphere Surface of the Sun made of churning gases of churning gases Lowest temperatures of all of the layers (5500 o C) The Sun’s yellow colour originates in the photosphere. We see this because it is brighter than the chromosphere.

7. The Chromosphere Is a thin layer of atmosphere above the photosphere (hotter than the photosphere) Has a red colour to it which we can only see during a total solar eclipse.

8. Extends beyond the chromosphere for millions of kilometers Again most clearly visible during a solar eclipse The corona is hotter than the photosphere because the gases are ionized. The Corona

9. Magnetic Fields Earth has its own magnetic field (caused by spinning molten metal deep in the Earth’s core) The Sun has a magnetic field generated by the movement of plasma deep in the Sun’s interior.

10. Sunspots Occur in the photosphere Indicate areas where the magnetic field is strong which prevents the plasma from mixing thus allowing it to cool to form the darker spots

11. Prominence Bright streams of plasma extending from the photosphere into the corona The plasma is electrically charged and can be shaped by the magnetic field of the Sun Can last for days or weeks

12. Solar flares Most solar flares occur near sunspots (thought to be a result of magnetic fields) Occur in the chromosphere and the corona It is a huge outbreak of electrified particles that are thrown into space at a speed of 1000 km/s. (spits out particles so fast that they cannot be trapped by the Sun’s gravity.) If directed at the Earth, they are diverted from the surface towards the poles.

13. Coronal Mass Ejection An extremely powerful kind of flare. If directed at the Earth it can damage satellites. Astronauts on shuttles and the space station must go to areas which offer more protection from the cosmic radiation They are diverted from the Earth’s surface by our magnetic field towards the poles. This can create auroras.

14. When these charged particles hit the earth's atmosphere, they excite the atoms contained in the atmosphere. These excited atoms have a higher energy state than usual and so want to get back to a more normal energy state. The excited atoms give off excess energy in the form of heat, or in the case of the aurora borealis, light. Aurora Borealis

15. Occur at the poles Aurora borealis

16. Solar Wind Steady stream of charged particles from the Sun’s surface in all directions