Near-Earth Space: The Van Allen Belts

1. Near-Earth Space: The Van Allen Belts

2. Nature of the Belts • Discovered early in the space age with a Geiger counter. • Energetic charged particles are trapped in the Earth’s magnetic field. • The inner belt contains protons, and the outer contains electrons. • The inner belt begins at only 100 km or so above ground.

3. Aurorae

4. Space Aurora

5. Aurora Borealis from Yellowknife in Canada

6. Aurorae • Solar wind particles are generally repelled by the magnetosphere, but some “sneak” into the atmosphere by running along magnetic field lines toward the poles. (Outer belt) • Earth atmospheric particles sneak into the belts as well. (Inner belt) • At ~100km altitude, solar wind particles collide with atmosphere particles to produce an auroral light display.

7. Comparison of Planetary Magnetic Fields

8. The space around the Earth is not exactly crowded, but there is a great deal of “space debris” in orbit around Earth.

10. Cosmic Rays: The penetration of energetic particles from space into the Earth’s atmosphere

11. The Earth at Night (light pollution)

12. Sky Appearance

13. Understanding Sky Color

14. Sky Color from Two Places

15. Structure of the Earth’s Atmosphere

16. The Ozone Layer Component

17. Antarctic Ozone Hole

18. Ozone Layer Ozone molecule = O3 O3 protects use from harmful solar UV radiation An efficient O3 destruction mechanism involves chlorofluorocarbons (CFC’s – Cl, F, C): <chemistry> … A single Cl atom can be used 1000’s of times to break up ozone molecules! Catalyst

19. Ozone Trends South Pole North Pole

20. Energy Budget of the Earth

21. Global Warming: Trends and Effects • The topic of global warming is complicated. The question is not whether warming exists, but its origin. • Increased greenhouse gases (carbon dioxide, methane, etc) act like a blanket to block the escape of infrared “heat” light. • The Earth has also undergone cycles in the past. • The main concern is the impact and control of warming.

22. Climate Regulation

24. The Earth's surface absorbs energy from sunlight and then radiates about as much energy back into space. The best proof you can offer for this fact is that the average surface temperature on Earth is a) warming slowly. b) not warming rapidly. c) half light and half dark. d) warmer at the core than on the surface. Share Question

25. Weather Primarily driven by solar radiation. Other significant influences include: • Land mass and oceans • Planet rotation • Atmospheric composition • Ozone • Greenhouse effect • Volcanic activity

26. The Hadley Cell: Fundamental circulation pattern because of the fact that planets are round.

27. Coriolis Deflection: Planet rotation causes north-south weather circulation to deflect east-west.

28. The Coriolis Force

29. Hadley Cells on the Earth

30. Volcanoes and Resurfacing • Magma is less dense than rock, and so rises from the interior • This breaks through, giving a volcano • Products • New rocks (esp. basalts) • Ash ( ~1mm ) • Cinders (~ 1cm ) • The key point is that volcanoes lead to resurfacing and are evidence of an active planetary interior

31. Mount St. Helens

32. Tungurahua (Andes)

33. Igneous (“ignus”=fire) - form from crystallization of molten rock Magma - molten inside earth Lava - molten on surface Of planetary interest: Basalt - fast cooling Granite - slow cooling Sedimentary - formed by deposition of small particles which become cemented (e.g., sandstone, shales) Metamorphic - changed by heat, pressure, and/or chemistry (e.g., marble) Rock Types

34. Crustal Plates and Tectonic Activity • Earth’s surface (or crust) is not a single solid piece, but consists of large and small “plates” • These plates slowly drift around • At points of convergence, get volcanoes, mountain ranges, and earthquakes

35. Crustal Plates

36. Long Term Plate Drifting

37. Plate Motion

38. Volcanic Activity on Earth and Relation to Motion of Plates

39. Recycling process and resurfacing effects

40. Interior Structure of the Earth

41. Detail of Earth Interior

42. Seismology Study of the Earth’s interior from how it carries vibrations • Types of vibrations • P-waves: pressure waves that travel like sound • S-waves: shear waves, like on a rope • Terminology: • Focus: point at which the earthquake originates • Epicenter: surface point above the focus • Seismometer: a device to measure P & S waves and the strength of earthquakes

43. Earthquake

44. Wave Forms

45. Refraction of traveling sound waves in the Earth reveals its components

46. Shuddering of the Earth

47. Earthquakes are an important tool for scientists because their vibrations a) influence the Earth's orbit about the Sun b) allow the study of the Earth's internal structure c) inform us of the mass of the Earth d) are used to predict the future of plate tectonics Share Question

48. Earth’s Magnetic Field • Lines of force are somewhat like a bar magnet. • Its origin and maintenance comes from dynamo activity in the core: • Circulation of conducting fluid (e.g., molten metals) generates magnetic fields. • So, planetary magnetic fields act like probes of unseen planetary interiors

49. Earth Dynamo

50. The Earth's magnetic dynamo is caused by a combination of convection in its molten core and a) the Earth's orbit around the Sun b) the Earth's rotation c) lunar tidal action d) the aurora borealis Share Question